JP7489648B2 - Distributed power supply system, control device and control method - Google Patents

Description

This disclosure relates to a distributed power system, a control device, and a control method.

Distributed power supply systems are known. Distributed power supply systems may include multiple power generation devices. An example of such a distributed power supply system is described in Patent Document 1.

The distributed power system 100 described in Patent Document 1 is shown in FIG. 7. The distributed power system 100 includes a power generation device 110, a DC bus 104, a power storage device 102, a grid interconnection device 108, and an overall control device 109.

The power generation device 110 generates power using renewable energy. Specifically, the power generation device 110 is a solar power generation device. The power generation device 110 includes a solar cell 101 and a DC-DC converter 103. The DC-DC converter 103 converts the DC voltage output from the solar cell 101 into a DC voltage of a predetermined magnitude.

The power storage device 102 is connected to the DC-DC converter 103 via the DC bus 104. The power storage device 102 is supplied with the power generated by the power generation device 110 and is charged with that power.

The grid interconnection device 108 has a DC-AC inverter 107. The DC-AC inverter 107 inversely converts the DC power from the power storage device 102 into AC power that can be interconnected with the power grid 105. The power obtained by the inverse conversion is supplied to the load 106 and the power grid 105.

The control device 109 receives forecast data on the amount of power generation. Based on the forecast data on the amount of power generation and the forecast power consumption, the control device 109 sets a target value for the remaining charge of the power storage device 102. Based on the target value and actual value of the remaining charge, the control device 109 changes the output of the grid interconnection device 108 in fixed time units.

JP 2012-75224 A

This disclosure provides technology that can contribute to the realization of an inexpensive distributed power system suitable for stabilizing the power supplied to a load from a commercial power source.

The present disclosure relates to
a plurality of power generating units including a first power generating unit;
a power storage device connected to the plurality of power generation devices;
a power output device including a power input unit connected to the plurality of power generation devices and the power storage device, and a power output unit connected to a commercial power source via a branch unit to which a load is connected;
A detection device;
a control device that causes a specific power, which is a value representing the power received from the commercial power source and is determined using the detection device, to follow a certain target power,
When the generated power of the first power generation device is defined as a first generated power, and a value that indicates the charging power of the power storage device when it is positive and indicates the discharging power of the power storage device when it is negative is defined as the charging/discharging power of the power storage device, the control device:
Calculating a difference power by subtracting the specific power from the target power;
When the difference power is greater than zero, in a case where a second process for increasing the charge/discharge power is to be executed, a first process for decreasing the first generated power is executed before the second process is executed;
When the difference power is smaller than zero, in a case where a fourth process for decreasing the charge/discharge power is to be executed, a third process for increasing the first generated power is executed before the fourth process is executed.
Provides a distributed power system.

The technology disclosed herein can contribute to the realization of an inexpensive distributed power system suitable for stabilizing the power supplied to a load from a commercial power source.

FIG. 1A is a configuration diagram of a distributed power system according to an embodiment. FIG. 1B is a configuration diagram of a distributed power supply system according to an embodiment. FIG. 2A is a configuration diagram of a Rankine cycle power generation power source according to an embodiment. FIG. 2B is a configuration diagram of a power converter according to the embodiment. FIG. 3 is a configuration diagram of a solar power generation device according to an embodiment. FIG. 4 is a configuration diagram of the power storage device according to the embodiment. FIG. 5 is a control flow chart according to the embodiment. FIG. 6A is a diagram illustrating changes in power over time according to the embodiment. FIG. 6B is a diagram illustrating the change in power over time in the comparative example. FIG. 6C is a diagram illustrating the change in power over time in the comparative example. FIG. 6D is a diagram illustrating the change in power over time in the comparative example. FIG. 6E is a diagram illustrating changes in power over time in the comparative example. FIG. 7 is a configuration diagram of a conventional distributed power system.

(Findings that form the basis of this disclosure)
There are known power generation devices that utilize renewable energy such as sunlight. The power generated by such power generation devices is prone to fluctuations due to the natural environment. Patent Literature 1 describes that the fluctuations in the power generation are absorbed by a power storage device.

However, the power generated by a power generation device that uses renewable energy can fluctuate significantly. For this reason, if fluctuations in generated power are absorbed by a power storage device as described in Patent Document 1, a large-capacity power storage device is required. However, large-capacity power storage devices are expensive.

Patent Document 1 also describes that a target value for the remaining charge of the storage device is set based on predicted data on the amount of power generated. However, the predictions may not be accurate. If the predictions are incorrect, the storage device may be in a fully charged state or an over-discharged state. In these states, it may not be possible to absorb fluctuations in the amount of power generated.

Here, let us consider a case where the power required by the load is supplied by the power generated by a power generation device using renewable energy and the power received from a commercial power source. In this case, when the generated power fluctuates, the received power will also fluctuate accordingly.

If the power received from a commercial power source is unstable, it is difficult to balance power supply and demand, and the voltage of the commercial power source is prone to fluctuations.

For these reasons, technology that can realize an inexpensive distributed power system suitable for stabilizing the power supplied to a load from a commercial power source is worthy of consideration.

(Summary of one aspect of the present disclosure)
A distributed power supply system according to a first aspect of the present disclosure includes:
a plurality of power generating units including a first power generating unit;
a power storage device connected to the plurality of power generation devices;
a power output device including a power input unit connected to the plurality of power generation devices and the power storage device, and a power output unit connected to a commercial power source via a branch unit to which a load is connected;
A detection device;
a control device that causes a specific power, which is a value representing the power received from the commercial power source and is determined using the detection device, to follow a certain target power,
When the generated power of the first power generation device is defined as a first generated power, and a value that indicates the charging power of the power storage device when it is positive and indicates the discharging power of the power storage device when it is negative is defined as the charging/discharging power of the power storage device, the control device:
Calculating a difference power by subtracting the specific power from the target power;
When the difference power is greater than zero, in a case where a second process for increasing the charge/discharge power is to be executed, a first process for decreasing the first generated power is executed before the second process is executed;
When the differential power is smaller than zero, in a case where a fourth process for decreasing the charge/discharge power is to be executed, a third process for increasing the first generated power is executed before executing the fourth process.

The technology according to the first aspect can contribute to the realization of an inexpensive distributed power system suitable for stabilizing the power supplied from a commercial power source to a load.

In a second aspect of the present disclosure, for example, in the distributed power supply system according to the first aspect,
The control device may update a command first generated power of the first power generation device at a certain control period,
The first generated power may follow the command first generated power of the first power generation device,
The control period may be 1 millisecond or less.

The second aspect is suitable for controlling the first generated power with high responsiveness.

In a third aspect of the present disclosure, for example, in the distributed power supply system according to the first or second aspect,
The first power generation device may be a thermal power generation device that generates electricity by utilizing heat, or a fuel cell power generation device.

The power generation device of the third aspect is a specific example of the first power generation device.

In a fourth aspect of the present disclosure, for example, in the distributed power system according to any one of the first to third aspects,
The plurality of power generation units may include a second power generation unit,
The second power generation device may be a power generation device that utilizes renewable energy.

The second power generation device of the fourth aspect uses renewable energy. Such a second power generation device has the advantage of having a small environmental impact, but the disadvantage that the generated power may fluctuate depending on the natural environment. However, the second power generation device of the fourth aspect is combined with the technology of the first aspect. This makes it possible to obtain the above advantages while minimizing the above disadvantages.

In a fifth aspect of the present disclosure, for example, in the distributed power system according to the fourth aspect,
The second power generation device may be a solar power generation device or a wind power generation device.

The fifth aspect of the power generation device is a specific example of a power generation device that uses renewable energy.

In a sixth aspect of the present disclosure, for example, in the distributed power system according to any one of the first to fifth aspects,
The control device may set a lower limit power that is a lower limit of a command first generated power that the first generated power should follow, and an upper limit power that is an upper limit of the command first generated power,
The second process may be started when the command first generated power reaches the lower limit power by the first process.
The fourth process may be started when the command first generated power reaches the upper limit power by the third process.

According to the sixth aspect, the adjustment of the power received from the commercial power source by adjusting the first generated power can be performed within a reasonable range for the first power generating device.

In a seventh aspect of the present disclosure, for example, in the distributed power system according to any one of the first to sixth aspects,
The operation mode executed by the control device may include a first mode in which any one of a plurality of processes including the first process, the second process, the third process, and the fourth process is selected and executed,
The first generated power at a start of the first mode may be greater than zero and less than a rated value of the first generated power.

According to the seventh aspect, after the first mode is started, the state in which the first generated power can be increased or decreased tends to continue. This is suitable for suppressing charging and discharging of the power storage device. Operation that tends to suppress charging and discharging makes it possible to use an inexpensive power storage device with a limited capacity.

In an eighth aspect of the present disclosure, for example, the distributed power system according to any one of the first to seventh aspects includes:
an AC circuit extending from the power output section to the commercial power source, the AC circuit including a first portion between the power output section and the branch portion and a second portion between the branch portion and the commercial power source;
A branch electric path extending from the branch portion to the load,
The detection device includes:
(i) a current detector disposed in the second portion; or
(ii) The power supply may include a current detector provided in the branch electric circuit.

The eighth aspect of the current detector is useful for determining a specific power.

A control device according to a ninth aspect of the present disclosure includes:
a plurality of power generating units including a first power generating unit;
a power storage device connected to the plurality of power generation devices;
a power output device including a power input unit connected to the plurality of power generation devices and the power storage device, and a power output unit connected to a commercial power source via a branch unit to which a load is connected;
a detection device, and a control device that controls a distributed power system so that a specific power, which is a value representing power received from the commercial power source and is determined using the detection device, follows a certain target power,
When the generated power of the first power generation device is defined as a first generated power, and a value that indicates the charging power of the power storage device when it is positive and indicates the discharging power of the power storage device when it is negative is defined as the charging/discharging power of the power storage device, the control device:
Calculating a difference power by subtracting the specific power from the target power;
When the difference power is greater than zero, in a case where a second process for increasing the charge/discharge power is to be executed, a first process for decreasing the first generated power is executed before the second process is executed;
When the differential power is smaller than zero, in a case where a fourth process for decreasing the charge/discharge power is to be executed, a third process for increasing the first generated power is executed before executing the fourth process.

The technology according to the ninth aspect can contribute to the realization of an inexpensive distributed power system suitable for stabilizing the power supplied from a commercial power source to a load.

A control method according to a tenth aspect of the present disclosure includes:
a plurality of power generating units including a first power generating unit;
a power storage device connected to the plurality of power generation devices;
a power output device including a power input unit connected to the plurality of power generation devices and the power storage device, and a power output unit connected to a commercial power source via a branch unit to which a load is connected;
A control method for controlling a distributed power system including a detection device, so that a specific power, which is a value representing power received from the commercial power source and is determined using the detection device, follows a certain target power, comprising:
When the generated power of the first power generation device is defined as a first generated power, and a value indicating the charging power of the power storage device when it is positive and indicating the discharging power of the power storage device when it is negative is defined as the charging/discharging power of the power storage device,
calculating a difference power by subtracting the specific power from the target power;
When the difference power is greater than zero, in a case where a second process for increasing the charge/discharge power is to be executed, a first process for decreasing the first generated power is executed before the second process is executed.
When the differential power is smaller than zero, in a case where a fourth process of decreasing the charging/discharging power is to be executed, a third process of increasing the first generated power is executed before the fourth process is executed.
including.

The technology according to the tenth aspect can contribute to the realization of an inexpensive distributed power system suitable for stabilizing the power supplied from a commercial power source to a load.

The following describes embodiments of the present disclosure with reference to the drawings. The present invention is not limited to the following embodiments.

(Embodiment 1)
FIG. 1A shows a distributed power system 1 according to the first embodiment.

The distributed power system 1 shown in FIG. 1A includes a plurality of power generation devices 32, a power output device 6, a control device 8, a power storage device 9, and a detection device 71.

The power generation devices 32, the power storage device 9, and the power output device 6 are connected to each other. Specifically, this connection is made via a DC circuit 35.

The distributed power system 1 can be connected to a commercial power source 5A and a load 5B. Specifically, the power output device 6, the commercial power source 5A, and the load 5B can be connected to each other. More specifically, this connection can be made via an AC circuit 36.

The power generated by the multiple power generation devices 32 can be supplied to the power storage device 9. The power generated by the multiple power generation devices 32 and the power stored in the power storage device 9 can be supplied to the load 5B via the power output device 6. The load 5B can also be supplied with power from the commercial power source 5A.

In one example, power is supplied from distributed power system 1 to load 5B. If this power supply is not enough to cover the power required by load 5B, the shortfall is supplied from commercial power source 5A to load 5B. There is no reverse power flow from distributed power system 1 to commercial power source 5A.

In another example, power may flow back from the distributed power system 1 to the commercial power source 5A.

Load 5B is not particularly limited. In one example, load 5B is electrical equipment in a factory. In another example, load 5B is a household electrical appliance.

The components of the distributed power system 1 are described below.

The multiple power generation devices 32 include a first power generation device 3 and a second power generation device 2. In this embodiment, the multiple power generation devices 32 are two power generation devices, the first power generation device 3 and the second power generation device 2. However, the multiple power generation devices 32 may further include other power generation devices.

The first power generating device 3 is connected to the DC circuit 35. The first power generating device 3 has power generation adjustment capability. Having power generation adjustment capability means that the power generated by the first power generating device 3 can be increased or decreased by controlling the power generated by the first power generating device 3. In this embodiment, the power generated by the first power generating device 3 can be increased or decreased sequentially by controlling the control device 8.

In the example of FIG. 1A, the first power generation device 3 includes a power generation source 3R and a power converter 3H.

The power generation source 3R generates electricity. The power generation source 3R has power generation adjustment capability. In this embodiment, the power generated by the power generation source 3R can be increased or decreased sequentially under the control of the control device 8.

Hereinafter, the generated power of the first power generation device 3 may be referred to as a first generated power _P1 . Specifically, the first generated power _P1 is DC power. The first generated power _P1 is output to a DC circuit 35. In the example of Fig. 1A, the first generated power _P1 is the output power of the power converter 3H.

In this embodiment, the first power generation device 3 is a thermal power generation device that uses heat to generate power. Specifically, the first power generation device 3 is an exhaust heat power generation device that uses exhaust heat to generate power. In this embodiment, the first power generation device 3 is a Rankine cycle power generation device.

In this embodiment, the power source 3R is a power source that generates power using heat. Specifically, the power source 3R is a power source that generates power using exhaust heat. In this embodiment, the power source 3R is a Rankine cycle power source.

In the above description of the power generation device and power source that generate electricity using exhaust heat, an example of a source of exhaust heat is a factory. A specific example of a source of exhaust heat is a furnace. For example, this furnace is a furnace used in the manufacture of castings.

In this embodiment, the power converter 3H is an AC-DC converter.

In the following, the first power generation device 3, which is a thermal power generation device, may be referred to as a thermal power generation device 3. The first power generation device 3, which is an exhaust heat power generation device, may be referred to as an exhaust heat power generation device 3. The first power generation device 3, which is a Rankine cycle power generation device, may be referred to as a Rankine cycle power generation device 3. The power generation source 3R, which is a Rankine cycle power generation source, may be referred to as a Rankine cycle power generation source 3R. The power converter 3H, which is an AC-DC converter, may be referred to as an AC-DC converter 3H.

In another example, the first power generation device 3 is a fuel cell power generation device. The power generation source 3R is a fuel cell. The power converter 3H is a DC-DC converter.

As can be understood from the above description, in this embodiment, the Rankine cycle power generation device 3 includes a Rankine cycle power generation source 3R and an AC-DC converter 3H.

Figure 2A shows the Rankine cycle power generation power source 3R of this embodiment. The Rankine cycle power generation power source 3R of this embodiment includes a pump 3A, an evaporator 3B, a temperature sensor 3D, an expansion machine 3C, a bypass valve 3E, a condenser 3F, and a generator 3G.

In the Rankine cycle power generation source 3R, a refrigerant circulation path is formed. In this circulation path, a pump 3A, an evaporator 3B, an expander 3C, and a condenser 3F appear in this order.

The pump 3A circulates the refrigerant by pumping it. The evaporator 3B recovers heat from the heating medium and uses that heat to heat the refrigerant. The expander 3C expands the refrigerant. The condenser 3F condenses the refrigerant by removing heat from the refrigerant. The heat removed by the condenser 3F is given to the cooling medium.

In this embodiment, the heating medium is gas. More specifically, the heating medium is exhaust gas. In other words, the Rankine cycle power generation source 3R is a power generation source that uses exhaust heat. The source of the exhaust gas is, for example, a factory, and in one specific example, a furnace, which may be a furnace used in the manufacture of castings. The evaporator 3B is, for example, a fin-and-tube heat exchanger.

In this embodiment, the refrigerant becomes a high-pressure gas by heating in the evaporator 3B. The expander 3C expands the high-pressure gas refrigerant.

In this embodiment, the cooling medium is a gas. Specifically, the cooling medium is air in the atmosphere. However, the cooling medium may be a liquid such as water. The condenser 3F may be equipped with a fan. The condenser 3F is, for example, a fin-and-tube heat exchanger, a plate heat exchanger, or a double-tube heat exchanger.

A bypass passage for the refrigerant is formed in the Rankine cycle power generation source 3R. The bypass passage bypasses the expander 3C. Specifically, the bypass passage connects a portion of the circulation passage downstream of the evaporator 3B and upstream of the expander 3C to a portion of the circulation passage downstream of the expander 3C and upstream of the condenser 3F.

The bypass valve 3E is provided in the bypass path. By making the opening of the bypass valve 3E non-zero, some or all of the refrigerant flowing through the circulation path can be made to flow into the bypass valve 3E.

The bypass valve 3E may be a flow rate control valve or an on-off valve. Here, a flow rate control valve is a valve that can have an opening degree greater than 0% and less than 100%. An on-off valve is a valve whose opening degree can be set to one of two values, 0% and 100%.

The temperature sensor 3D is provided in a portion of the circulation path downstream of the evaporator 3B and upstream of the expander 3C. The temperature sensor 3D detects the temperature of the refrigerant in this portion. The temperature sensor 3D can be used to control the components of the Rankine cycle power generation device 3. Specifically, the temperature sensor 3D is provided in a portion of the circulation path upstream of the branch point to the bypass path. The temperature detected by the temperature sensor 3D can be substantially the inlet temperature of the expander 3C.

The generator 3G is connected to the expander 3C. In the expander 3C, rotational energy is generated by expansion. In the generator 3G, the rotor rotates due to the rotational energy. In this way, AC power is generated in the generator 3G.

The AC-DC converter 3H is connected to the generator 3G. The AC-DC converter 3H is supplied with AC power generated by the generator 3G. The AC-DC converter 3H converts this AC power into DC power.

The configuration of AC-DC converter 3H of this embodiment is shown in FIG. 2B. AC-DC converter 3H of this embodiment includes switching elements 16 to 21, diodes 51 to 56, and capacitor 22. Capacitor 22 is an output capacitor.

The AC-DC converter 3H is configured with a first phase circuit 61, a second phase circuit 62, and a third phase circuit 63. The first phase circuit 61, the second phase circuit 62, and the third phase circuit 63 configure a switching circuit 60. The first phase circuit 61, the second phase circuit 62, the third phase circuit 63, and the capacitor 22 are connected in parallel with each other. The first phase circuit 61, the second phase circuit 62, and the third phase circuit 63 are each connected to the generator 3G.

In this embodiment, the first phase circuit 61, the second phase circuit 62, and the third phase circuit 63 are connected to the first phase, the second phase, and the third phase of the generator 3G, respectively. In this embodiment, the first phase, the second phase, and the third phase are the U phase, the V phase, and the W phase, respectively.

The first phase circuit 61 includes switching elements 16 and 17 and diodes 51 and 52. The switching elements 16 and 17 are connected in series via a first connection point 66. The switching element 16 and the diode 51 are connected in parallel. The switching element 17 and the diode 52 are connected in parallel.

The second phase circuit 62 includes switching elements 18 and 19 and diodes 53 and 54. The switching elements 18 and 19 are connected in series via a second connection point 67. The switching element 18 and the diode 53 are connected in parallel. The switching element 19 and the diode 54 are connected in parallel.

The third phase circuit 63 includes switching elements 20 and 21, and diodes 55 and 56. The switching elements 20 and 21 are connected in series via a third connection point 68. The switching element 20 and the diode 55 are connected in parallel. The switching element 21 and the diode 56 are connected in parallel.

In this embodiment, the first connection point 66 is connected to the first phase of the generator 3G. The second connection point 67 is connected to the second phase of the generator 3G. The third connection point 68 is connected to the third phase of the generator 3G.

The rotation speed of the generator 3G is controlled using the AC-DC converter 3H. More specifically, the switching of the switching elements 16 to 21 is controlled so that the AC-DC converter 3H applies regenerative braking to the generator 3G to obtain regenerative power. Control using the AC-DC converter 3H is performed by the control device 8. The capacitor 22 absorbs momentary pulsations in the regenerative power.

In one specific example, the switching elements 16 to 21 are driven by pulse width modulation (PWM). More specifically, a PWM signal is supplied to the switching elements 16 to 21. The switching elements 16 to 21 then switch based on the PWM signal.

In the example of FIG. 2B, the switching elements 16 to 21 are, for example, insulated gate bipolar transistors (IGBTs). However, the switching elements 16 to 21 may be other switching elements, such as metal oxide semiconductor field effect transistors (MOSFETs).

As can be understood from the above description, in this embodiment, the first power generation device 3 includes a generator 3G that generates power by rotation of a rotor, and a power converter 3H that includes a switching circuit 60. The control device 8 controls the rotation of the rotor using the switching circuit 60, thereby controlling the first generated power _P1 . This embodiment is suitable for controlling the first generated power _P1 with high responsiveness.

Specifically, the first generated power _P1 is controlled by a generator 3 using an AC-DC converter 3H.
This can be achieved by controlling the rotation speed of G. This control can be achieved by the control device 8.

A configuration may be adopted in which the flow rate of the refrigerant flowing through the circulation path is controlled by controlling the rotation speed of the pump 3A, thereby controlling the first generated power _P1 . A configuration may be adopted in which the flow rate of the refrigerant flowing through the circulation path is controlled by controlling the opening degree of the bypass valve 3E, thereby controlling the first generated power _P1 . A configuration may also be adopted in which a brake circuit is provided in the first power generating device 3, and a part of the DC power obtained by the first power generating device 3 is consumed in the brake circuit, thereby controlling the first generated power _P1 . These controls may also be executed by the control device 8. A configuration may also be adopted in which the first generated power P1 is controlled by combining two or more selected from the control of the rotation (specifically, the rotation speed) of the rotor, the control of the rotation speed of the pump 3A, _the control of the opening degree of the bypass valve 3E, and the power consumption by the brake circuit.

The configuration of the AC-DC converter 3H shown in FIG. 2B can also be used when the power generating source 3R is not a Rankine cycle power generating source.

As can be understood from the above description, control of the rotation of the rotor using a switching circuit can be employed when the first power generating device is a Rankine cycle power generating device. In addition, this control can be employed when the first power generating device is another type of power generating device as long as the first power generating device has a rotor. Of course, this control can be employed whether the first power generating device is a Rankine cycle power generating device or not, as long as the first power generating device is a thermal power generating device such as an exhaust heat power generating device and has a rotor.

The number of power sources included in the first power generating device 3 is not limited to one. This number may be more than one. In this case, the first power generating device 3 may include the same number of power converters as the number of power sources, and the multiple power sources and the multiple power converters may be connected one-to-one. In this case, the power sources and the power converters may be the elements exemplified as the power source 3R and the power converter 3H. The multiple power sources may be different types of power sources, such as one power source being a Rankine cycle power source and another power source being a fuel cell. Also, the multiple power sources may be the same type of power sources, such as one power source and another power source being a Rankine cycle power source. This also applies to the multiple power converters. In this case, the power output by the first power generating device 3 by the generation of the multiple power sources is referred to as the first generated power P ₁
This will be referred to as the "

Returning to FIG. 1A, the second power generating device 2 is connected to the DC circuit 35. During operation of the second power generating device 2, the power generated by the second power generating device 2 may vary depending on the weather, etc. Specifically, the second power generating device 2 is a power generating device that uses renewable energy.

In the example of FIG. 1A, the second power generation device 2 includes a power generation source 2A and a power converter 2B.

In this embodiment, the second power generation device 2 is a solar power generation device. Specifically, the power generation source 2A is a solar cell. The power converter 2B is a DC-DC converter.

In the following, the second power generation device 2, which is a solar power generation device, may be referred to as the solar power generation device 2. The power generation source 2A, which is a solar cell, may be referred to as the solar cell 2A. The power converter 2B, which is a DC-DC converter, may be referred to as the DC-DC converter 2B.

In another example, the second power generation device 2 is a wind power generation device. Specifically, the power generation source 2A is a wind turbine. The power converter 2B is a power converter that combines an AC-DC converter and a DC-DC converter.

Figure 3 shows a specific example of the second power generation device 2 according to this embodiment. In this specific example, the DC-DC converter 2B is a DC chopper circuit. Hereinafter, the DC-DC converter 2B, which is a DC chopper circuit, may be referred to as the DC chopper circuit 2B.

In the specific example shown in FIG. 3, the DC chopper circuit 2B includes capacitors 41 and 42, a switching element 13, a diode 57, a rectifier diode 14, and a reactor 15. Capacitor 41 is an input capacitor. Capacitor 42 is an output capacitor.

The switching element 13 and the diode 57 are connected in parallel.

The solar cell 2A, the reactor 15, and the switching element 13 are connected in this order. Current can flow through the solar cell 2A, the reactor 15, and the switching element 13 in this order.

Further, the solar cell 2A, the reactor 15, the rectifier diode 14, and the DC circuit 35 are connected in this order. A current can flow through the solar cell 2A, the reactor 15, the rectifier diode 14, and the DC circuit 35 in this order.

Specifically, a DC voltage is input from the solar cell 2A to the DC chopper circuit 2B. The switching of the switching element 13 is controlled. When the switching element 13 is on, a current flows from the solar cell 2A to the reactor 15 and the switching element 13 in this order, and energy is stored in the reactor 15. When the switching element 13 is off, a current flows from the solar cell 2A to the reactor 15 and the diode 14 in this order, and the energy stored in the reactor 15 is output via the diode 14. Through this operation, the DC chopper circuit 2B boosts the DC voltage input from the solar cell 2A and transmits power to the DC circuit 35 by passing a current through the diode 14. The control using the DC chopper circuit 2B is performed by the control device 8.

In one specific example, the switching element 13 is driven by pulse width modulation. More specifically, a PWM signal is supplied to the switching element 13. The switching element 13 then switches based on the PWM signal.

In one specific example, MPPT (Maximum Power Point Tracking) control of the solar cell 2A is performed. More specifically, the output current of the solar cell 2A is controlled using a DC chopper circuit 2B so that the power generated by the solar cell 2A is maximized.

In the example of FIG. 3, the switching element 13 is a MOSFET. However, the switching element 13 may be another switching element, such as an IGBT.

The configuration of the DC chopper circuit 2B shown in FIG. 3 can also be used when the power generation source 2A is not a solar cell.

Hereinafter, the generated power of the second power generation device 2 may be referred to as the second generated power _P2 . Specifically, the second generated power _P2 is DC power. The generated power _P2 is output to the DC circuit 35. In the example of Fig. 1A, the generated power _P2 is the output power of the power converter 2B.

In the following description, the sum of the power generated by the multiple power generation devices 32 may be referred to as the total generated power Psum. In this embodiment, the total generated power _Psum is the _sum of the generated power _P1 of the first power generation device 3 and the generated power P2 of the second power generation device ₂ .

The number of power sources included in the second power generating device 2 is not limited to one. This number may be multiple. In this case, the second power generating device 2 may include the same number of power converters as the number of power sources, and the multiple power sources and the multiple power converters may be connected one-to-one. In this case, the power sources and the power converters may be the elements exemplified as the power source 2A and the power converter 2B. The multiple power sources may be different types of power sources. Also, the multiple power sources may be the same type of power sources. This point is similar for the multiple power converters. In this case, the power output by the second power generating device 2 by the power generation of the multiple power sources is referred to as the second generated power _P2 .

Returning to FIG. 1A, the power storage device 9 is connected to a plurality of power generation devices 32. The power storage device 9 can be supplied with the power generated by the plurality of power generation devices 32. Specifically, the power storage device 9 is connected to the plurality of power generation devices 32 via a DC circuit 35. The power storage device 9 can function as a power buffer when the power generated by the plurality of power generation devices 32 is insufficient or excessive.

In the present embodiment, the power storage device 9 is connected to the first power generation device 3 and the second power generation device 2. Therefore, the power storage device 9 can be supplied with electric power generated by the first power generation device 3 and the second power generation device 2. Specifically, the power storage device 9 is connected to the first power generation device 3 and the second power generation device 2 via a DC current path 35.

In the example of FIG. 1A, the power storage device 9 includes a power storage device 9A and a power converter 9B.

In this embodiment, the storage battery 9A is a storage battery. Hereinafter, the storage battery 9A may be referred to as storage battery 9A. Specific examples of the storage battery constituting the storage battery 9A include a lithium ion battery, a nickel metal hydride battery, a lead storage battery, etc.

Another example of the storage battery 9A is a capacitor. A specific example of the capacitor that constitutes the storage battery 9A is an electric double layer capacitor.

In this embodiment, the power converter 9B is a DC-DC converter. Specifically, the power converter 9B is a bidirectional DC-DC converter. More specifically, the power converter 9B is a bidirectional chopper circuit. Hereinafter, the power converter 9B, which is a bidirectional DC chopper circuit, may be referred to as a bidirectional DC chopper circuit 9B.

Here, a bidirectional DC-DC converter refers to a converter that can perform both the following: converting a DC voltage input from its first terminal into a DC voltage of a different magnitude and outputting it to its second terminal, and converting a DC voltage input from its second terminal into a DC voltage of a different magnitude and outputting it to its first terminal.

Similarly, a bidirectional chopper circuit refers to a chopper circuit that can perform both the following: converting a DC voltage input from its first terminal into a DC voltage of a different magnitude and outputting it to its second terminal; and converting a DC voltage input from its second terminal into a DC voltage of a different magnitude and outputting it to its first terminal.

Figure 4 shows a specific example of the storage device 9 according to this embodiment.

In the specific example shown in FIG. 4, the bidirectional chopper circuit 9B includes switching elements 10 and 11, diodes 58 and 59, a reactor 12, and capacitors 46 and 47. Capacitors 46 and 47 are input and output capacitors.

The switching element 10 and the diode 58 are connected in parallel. The switching element 11 and the diode 59 are connected in parallel.

The DC circuit 35, the switching element 10, the reactor 12, and the storage battery 9A are connected in this order. Current can flow through the DC circuit 35, the switching element 10, the reactor 12, and the storage battery 9A in this order.

The diode 59, the reactor 12, and the storage battery 9A are connected in this order. Current can flow through the diode 59, the reactor 12, and the storage battery 9A in this order.

The storage battery 9A, the reactor 12, and the switching element 11 are connected in this order. Current can flow through the storage battery 9A, the reactor 12, and the switching element 11 in this order.

The storage battery 9A, the reactor 12, the diode 58, and the DC circuit 35 are connected in this order. Current can flow through the storage battery 9A, the reactor 12, the diode 58, and the DC circuit 35 in this order.

When charging the storage battery 9A, the switching element 11 is maintained in the off state. The switching of the switching element 10 is controlled. When the switching element 10 is on, a current flows through the switching element 10, the reactor 12, and the storage battery 9A in this order. When the switching element 10 is off, the reactor 12 tries to maintain the current flowing through it, and a current flows through the diode 59, the reactor 12, and the storage battery 9A in this order. Through this operation, the bidirectional chopper circuit 9B functions as a step-down chopper. In other words, the bidirectional chopper circuit 9B steps down the DC voltage input from the DC circuit 35, and charges the storage battery 9A by controlling the current of the reactor 12 with the stepped-down voltage.

When discharging from the storage battery 9A, the switching element 10 is maintained in the off state. The switching of the switching element 11 is controlled. When the switching element 11 is on, a current flows from the storage battery 9A to the reactor 12 and the switching element 11 in this order, and energy is stored in the reactor 12. When the switching element 11 is off, a current flows from the storage battery 9A to the reactor 12 and the diode 58 in this order, and the energy stored in the reactor 12 is output via the diode 58. Through this operation, the bidirectional chopper circuit 9B functions as a boost chopper. In other words, the bidirectional chopper circuit 9B boosts the DC voltage input from the storage battery 9A and transmits power to the DC circuit 35 by passing a current through the diode 58.

Control using the bidirectional chopper circuit 9B is performed by the control device 8.

In one specific example, switching element 10 is driven by pulse width modulation. More specifically, a PWM signal is supplied to switching element 10. Then, switching element 10 switches based on the PWM signal. The same is true for switching element 11.

When discharging from the storage battery 9A, synchronous rectification may be performed using the two switching elements 10 and 11. In synchronous rectification, when one of the switching elements 10 and 11 is on, the other is off, and when one is off, the other is on. In synchronous rectification, the two switching elements are turned on and off in a complementary manner in this way, which can reduce conduction loss compared to diode rectification using diodes. Specifically, synchronous rectification can be achieved by turning on switching element 10 during the period when current flows through diode 58 in the above description.

In the DC chopper circuit 2B shown in FIG. 3, the diode 14 may be replaced with a switching element X, and synchronous rectification may be performed using the switching element X and the switching element 13. Specifically, synchronous rectification can be achieved by turning on the switching element X during the period in which current flows through the diode 14 as described above.

In the example of FIG. 4, the switching elements 10 and 11 are, for example, MOSFETs. However, the switching elements 10 and 11 may be other switching elements, such as IGBTs.

The configuration of the bidirectional chopper circuit 9B shown in FIG. 4 can also be used when the storage battery 9A is not a storage battery.

Hereinafter, the charge/discharge power of the power storage device 9 may be referred to as P _storage . Here, the charge/discharge power that is positive indicates the charge power, and the absolute value of the charge/discharge power that is negative indicates the discharge power. Specifically, the charge/discharge power P _storage is DC power. The charge/discharge power P _storage is input/output to/from the DC circuit 35. In the example of FIG. 1A, the charge/discharge power P _storage is the input/output power of the bidirectional chopper circuit 9B.

The number of electric storage devices included in the electric storage device 9 is not limited to one. This number may be more than one. In this case, the electric storage device 9 may include the same number of power converters as the number of electric storage devices, and the multiple electric storage devices and the multiple power converters may be connected one-to-one. In this case, the electric storage devices and the power converters may be the elements exemplified as the electric storage device 9A and the power converter 9B. The multiple electric storage devices may be different types of electric storage devices. Also, the multiple electric storage devices may be the same type of electric storage devices. This point is similar for the multiple power converters. Also, in this case, the power that is charged and discharged by the second power generation device 2 by charging and discharging the multiple electric storage devices is referred to as charging and discharging power P _storage .

Returning to FIG. 1A, the power output device 6 includes a power input section 6i and a power output section 6о.

The power input unit 6i is connected to a plurality of power generation devices 32 and a power storage device 9. Specifically, the power input unit 6i is connected to the plurality of power generation devices 32 and the power storage device 9 via a DC circuit 35.

As shown in FIG. 1A, a load 5B is connected to the branch BP. The power output unit 6о is connected to a commercial power source 5A via the branch BP. Specifically, the power output unit 6о is connected to the commercial power source 5A and the load 5B via an AC circuit 36.

The power input unit 6i receives DC power from a plurality of power generation devices 32 and a power storage device 9. The power output unit 6о outputs AC power. The power is converted from DC to AC between the power input unit 6i and the power output unit 6о.

Specifically, the power input unit 6i receives power obtained by subtracting the charging/discharging power _Pstorage of the power storage device 9 from the total generated power _Psum . That is, when the power storage device 9 is being charged, the power input unit 6i receives power obtained by subtracting the charging power of the power storage device 9 from the total generated power _Psum . When the power storage device 9 is being discharged, the power input unit 6i receives power obtained by summing up the total generated power _Psum and the discharged power of the power storage device 9. As described above, the total generated power _Psum is the sum of the generated powers of the multiple power generation devices 32.

In another example, the power is converted from DC to DC between the power input section 6i and the power output section 6о, and then converted from DC to AC.

As shown in FIG. 1A, an AC electric circuit 36 extends from the power output unit 6о to the commercial power source 5A. The AC electric circuit 36 includes a first portion 36a and a second portion 36b. The first portion 36a is the portion between the power output unit 6о and the branch portion BP. The second portion 36b is the portion between the branch portion BP and the commercial power source 5A. The branch electric circuit 37 extends from the branch portion BP to the load 5B.

The distributed power system 1 is configured to be able to identify the specific power _Pgrid . Here, the specific power _Pgrid is a value that represents the power received from the commercial power source 5A. The specific power _Pgrid is also a value that is identified using the detection device PD. In this embodiment, the specific power _Pgrid represents the active power received from the commercial power source 5A.

In the example of Fig. 1A, the distributed power system 1 includes a detection device 71 as the detection device PD. The specific power _Pgrid is identified using the detection device 71. The detection device 71 includes a current detector 71A, a voltage detector 71B, and a power calculation unit 71C.

The current detector 71A is provided in the second portion 36b. The current detector 71A detects the AC current flowing through the location where the current detector 71A is provided. In this embodiment, the current detector 71A detects the AC current received from the commercial power source 5A.

The voltage detector 71B is provided in the AC circuit 36. Specifically, the voltage detector 71B is provided in the first portion 36a. The voltage detector 71B detects the AC voltage applied to the position where the voltage detector 71B is provided. In this embodiment, the voltage detector 71B detects the AC voltage received from the commercial power source 5A.

The voltage detector 71B may be provided in the second portion 36b. The voltage detector 71B may also be provided in the branch electrical circuit 37.

The power calculation unit 71C calculates a specific power _Pgrid using the current detected by the current detector 71A and the voltage detected by the voltage detector 71B.

The example of Fig. 1B may also be adopted. In the example of Fig. 1B, the distributed power system 1 includes a detection device 81 as the detection device PD. The specific power P _grid is identified using the detection device 81. The detection device 81 includes a current detector 81A, a voltage detector 81B, and a power calculation unit 81C.

The current detector 81A is provided in the branch electric circuit 37. The current detector 81A detects the AC current flowing through the location where the current detector 81A is provided. In this embodiment, the current detector 81A detects the AC current supplied to the load 5B.

The voltage detector 81B is provided in the AC circuit 36. Specifically, the voltage detector 81B is provided in the first portion 36a. The voltage detector 81B detects the AC voltage applied to the position where the voltage detector 81B is provided. In this embodiment, the voltage detector 81B detects the AC voltage supplied to the load 5B.

The voltage detector 81B may be provided in the second portion 36b. The voltage detector 81B may also be provided in the branch electrical circuit 37.

The power calculation unit 81C calculates the load power P _load using the detected current of the current detector 81A and the detected voltage of the voltage detector 81B. The load power P _load represents the AC power supplied to the load 5B. In this example, the load power P _load represents the active power supplied to the load 5B.

Furthermore, in the example of FIG. 1B, the distributed power system 1 includes a detection device 7. The detection device 7 includes a current detector 7A, a voltage detector 7B, and a power calculation unit 7C.

The current detector 7A is provided in the first portion 36a. The current detector 7A detects the AC current flowing through the location where the current detector 7A is provided. In this embodiment, the current detector 7A detects the AC current output from the power output device 6.

The voltage detector 7B is provided in the AC circuit 36. Specifically, the voltage detector 7B is provided in the first portion 36a. The voltage detector 7B detects the AC voltage applied to the position where the voltage detector 7B is provided. In this embodiment, the voltage detector 7B detects the voltage output from the power output device 6.

The voltage detector 7B may be provided in the second portion 36b. The voltage detector 7B may be provided in the branch electric circuit 37.

The power calculation unit 7C calculates the output power _Pout using the detected current of the current detector 7A and the detected voltage of the voltage detector 7B. The output power _Pout represents the AC power output from the power output device 6. In this example, the output power _Pout represents the active power output from the power output device 6.

1B, the distributed power system 1 further includes a calculation device 85. The calculation device 85 calculates the specific power _Pgrid by using the output power _Pout and the load power _Pload . Specifically, the calculation device 85 calculates the specific power _Pgrid by subtracting the output power _Pout from the load power _Pload .

In the example of Fig. 1A, the detection device 71 includes a current detector 71A provided in the second portion 36b. In the example of Fig. 1B, the detection device 81 includes a current detector 81A provided in the branch electric path 37. Specifically, in the example of Fig. 1B, a detection device 7 separate from the detection device 81 further includes a current detector 7A provided in the first portion 36a. These current detectors are useful for determining the specific power _Pgrid .

In both the example of Fig. 1A and the example of Fig. 1B, the control device 8 makes the specific power _Pgrid follow a constant target power _Pgrid ^* . The control device 8 is configured to be able to control the first generated power _P1 of the first power generation device 3 and the charge/discharge power _Pstorage of the power storage device 9. In this embodiment, the control device 8 is configured to be able to also control the generated power _P2 of the second power generation device 2. Note that the illustrated detection devices 7, 71, and 81 are devices that detect power, and therefore may be referred to as power detection devices.

Hereinafter, an example of control of the generated power _P1 of the first power generation device 3 and the charge/discharge power _Pstorage of the power storage device 9 by the control device 8 will be described with reference to the flowchart of FIG.

In the following description, the command value that the first generated power _P1 should follow may be referred to as a command first generated power _P1 ^* . The command value that the charge/discharge power _Pstorage of the storage device 9 should follow may be referred to as a command charge/discharge power _Pstorage ^* .

In addition, in the following explanation, the expression "electric power is input to the control device 8" is used. This expression means that information representing that electric power is input to the control device 8.

In the example according to this description, the control device 8 sets the command first generated power P ₁ ^* to a value in the range of not less than the lower limit power P _min and not more than the upper limit power P _max . The lower limit power P _min and the upper limit power P _max are expressed as follows:
This can be set based on the capacity of the first power generation unit 3, the operating environment, etc.

The steps from "Start" to "End" in the flowchart in Figure 5 constitute one control cycle. The control device 8 can repeatedly execute this control cycle.

In step S1, the specific power P _grid is input to the control device 8.

After step S1, in step S2, the target power P _grid ^* is input to the control device 8. Specifically, the target power P _grid ^* is input to the control device 8 from the upper level control device.

After step S2, in step S3, the control device 8 calculates the differential power P _delta . The differential power P _delta is the difference obtained by subtracting the specific power P _grid from the target power P _grid ^* .

After step S3, in step S4, the control device 8 determines whether the first condition, the second condition, the third condition, the fourth condition, or the fifth condition is satisfied.

The first condition is that the differential power P _delta is zero. If the first condition is met, in step S5, the control device 8 maintains the command first generated power P ₁ ^* at the current value. Using a formula, P ₁ ^* set in step S5 is given by P ₁ ^* (s) = P ₁ ^* (s - 1).

Here, P ₁ ^* (s-1) indicates P ₁ ^* before it is updated in the current control cycle, and P ₁ ^* (s) indicates P ₁ ^* after it is updated in the current control cycle. The same is true for P _storage ^* .

Furthermore, if the first condition is met, in step S6, the control device 8 sets the command charge/discharge power P _storage ^* to zero. Using a formula, P _storage ^* set in step S6 is given by P _storage ^* (s)=P _delta =0.

The second condition is that the differential power P _delta is greater than zero and the command first generated power P ₁ ^* is greater than the lower limit power P _min . If the second condition is met, in step S7, the control device 8 reduces the command first generated power P ₁ ^* by a first step width P _width1 . Using a formula, P ₁ ^* set in step S7 is given by P ₁ ^* (s) = P ₁ ^* (s - 1) - P _width1 .

Furthermore, if the second condition is satisfied, in step S8, the control device 8 maintains the command charge/discharge power P _storage ^* at the current value. Using a formula, P _storage ^* set in step S8 is given by P _storage ^* (s)=P _storage ^* (s-1).

The third condition is that the differential power P _delta is smaller than zero and the command first generated power P ₁ ^* is smaller than the upper limit power P _max . If the third condition is met, in step S9, the control device 8 increases the command first generated power P ₁ ^* by the first step width P _width1 . Using a formula, P ₁ ^* set in step S9 is given by P ₁ ^* (s) = P ₁ ^* (s - 1) + P _width1 .

Furthermore, if the third condition is satisfied, in step S10, the control device 8 maintains the command charge/discharge power P _storage ^* at the current value. Using a formula, P _storage ^* set in step S10 is given by P _storage ^* (s)=P _storage ^* (s-1).

The fourth condition is that the differential power P _delta is greater than zero and the command first generated power P ₁ ^* is the lower limit power P _min . If the fourth condition is met, in step S11, the control device 8 maintains the command first generated power P ₁ ^* at the lower limit power P _min . Using a formula, P ₁ ^* set in step S11 is given by P ₁ ^* (s) = P _min .

Furthermore, if the fourth condition is met, in step S12, the control device 8 increases the command charge/discharge power P _storage ^* by the second step width P _width2 . Using a formula, P _storage ^* set in step S12 is given by P _storage ^* (s)=P _storage ^* (s-1)+P _width2 .

The fifth condition is that the differential power P _delta is smaller than zero and the command first generated power P ₁ ^* is the upper limit power P _max . If the fifth condition is met, in step S13, the control device 8 maintains the command first generated power P ₁ ^* at the upper limit power P _max . Using a formula, P ₁ ^* set in step S13 is given by P ₁ ^* (s) = P _max .

Furthermore, if the fifth condition is met, in step S14, the control device 8 reduces the command charge/discharge power P _storage ^* by the second step width P _width2 . Using a formula, P _storage ^* set in step S14 is given by P _storage ^* (s)=P _storage ^* (s-1)-P _width2 .

After steps S5 and S6, after steps S7 and S8, after steps S9 and S10, after steps S11 and S12, or after steps S13 and S14, steps S15 and S16 are performed. In step S15, the control device 8 transmits a command first generated power P ₁ ^* to the first power generation device 3. In step S16, the control device 8 transmits a command charge/discharge power P _storage ^* to the storage device 9.

By repeating the control cycle of Fig. 5, the command first generated power _P1 ^* and the command charge/discharge power _Pstorage ^* can be successively updated. The first generated power _P1 of the first power generation device 3 follows the command first generated power _P1 ^* . The charge/discharge power _Pstorage of the storage device 9 follows the command charge/discharge power _Pstorage ^* . In this manner, the first power generation device 3 and the storage device 9 are controlled by the control device 8.

In this embodiment, the control cycle is repeated in a control period _Tp . Specifically, the control cycle includes updating of the command first generated power _P1 ^* in the control device 8, transmission of the command first generated power _P1 ^* from the control device 8 to the first power generation device 3, updating of the command charge/discharge power _Pstorage ^* in the control device 8, and transmission of the command charge/discharge power _Pstorage ^* from the control device 8 to the power storage device 9. The update of the command first generated power _P1 ^* in the control device 8 is repeated in a control period _Tp . The transmission of the command first generated power _P1 ^* from the control device 8 to the first power generation device 3 is repeated in a control period _Tp . The update of the command charge/discharge power _Pstorage ^* in the control device 8 is repeated in a control period _Tp . The transmission of the command charge/discharge power _Pstorage ^* from the control device 8 to the power storage device 9 is repeated in a control period _Tp .

As can be understood from the above description, in this embodiment, the control device 8 updates the command first generated power P ₁ ^* of the first power generating device 3 at a certain control period T _p . The first generated power P ₁ follows the command first generated power P ₁ ^* of the first power generating device 3. The control period T _p is, for example, 1 millisecond or less, and in one specific example, 100 microseconds or less. Doing so is suitable for controlling the first generated power P ₁ with high responsiveness. Specifically, by doing so, even if the generated power of a power generating device other than the first power generating device 3, such as the second generated power P ₂ , fluctuates instantaneously, the first generated power P ₁ can be controlled with high responsiveness to the fluctuation, and the total generated power P _sum can be stabilized. This makes it possible to stabilize the power received from the commercial power source 5A. This is advantageous from the viewpoint of maintaining a good power supply and demand balance. More specifically, by doing so, it is possible to control the first generated power P ₁ on the order of 10 milliseconds or on the order of milliseconds. The control period T _p is, for example, 100 nanoseconds or more, and may be 1 microsecond or more.

In this embodiment, the control device 8 updates the command charge/discharge power P _storage ^* of the storage device 9 at a certain control period T _p . The charge/discharge power P _storage follows the command charge/discharge power P _storage ^* of the storage device 9. An example of the numerical value of the control period T _p is as described above.

Hereinafter, the terms first process, second process, third process, and fourth process may be used. The first process is a process for decreasing the first generated power _P1 . The second process is a process for increasing the charge/discharge power _Pstorage . The third process is a process for increasing the first generated power _P1 . The fourth process is a process for decreasing the charge/discharge power _Pstorage .

As will be understood from the description with reference to Fig. 5, when the differential power P _delta is greater than zero, the control device 8 executes the first process before executing the second process in the case of executing the second process. Also, when the differential power P _delta is less than zero, the control device 8 executes the first process before executing the second process.
When the fourth process is to be executed, the third process is executed before the fourth process is executed.

As described above, the control device 8 prioritizes execution of the first process over the second process. Also, the control device 8 prioritizes execution of the third process over the fourth process. In this way, it is easier to suppress charging and discharging of the power storage device 9. This makes it possible to use an inexpensive power storage device 9 with a reduced capacity. For these reasons, prioritizing execution of the first process or the third process can contribute to the realization of an inexpensive distributed power system 1 suitable for stabilizing the power supplied from the commercial power source 5A to the load 5B. Also, suppressing the capacity of the power storage device 9 is advantageous from the viewpoint of miniaturization of the power storage device 9.

When the power supplied to the load from the commercial power source is stable, as in this embodiment, it can be said that the load power "from the perspective of the commercial power source" is stable. When the load power "from the perspective of the commercial power source" is stable, it is easier to balance the power supply and demand, and the voltage of the commercial power source is less likely to fluctuate.

Specifically, in this embodiment, the power required by the load 5B is met by the power from the power output device 6 and the power from the commercial power source 5A. The power storage device 9 can absorb fluctuations in the generated power _P2 of the power generation device 2 using renewable energy, so that even in a situation where such fluctuations occur, the power supplied from the power output device 6 to the load 5B can be stabilized. By stabilizing the power supplied from the power output device 6 to the load 5B, the power supplied from the commercial power source 5A to the load 5B can also be stabilized. Moreover, as described above, in this embodiment, the priority order of control is appropriately set. Therefore, the function of stabilizing the power supplied from the commercial power source 5A to the load 5B can be obtained by the inexpensive power storage device 9 with a reduced capacity. Therefore, the technology according to this embodiment can contribute to the realization of an inexpensive distributed power system suitable for stabilizing the load power "from the viewpoint of the commercial power source".

The power required by the load 5B may also change. Even in such a case, the control and storage device 9 makes it easy to suppress fluctuations in the power supplied from the commercial power source 5A to the load 5B.

The first process corresponds to at least one execution of step S7. The second process corresponds to at least one execution of step S12. The third process corresponds to at least one execution of step S9. The fourth process corresponds to at least one execution of step S14.

5, in the first and third processes, the command first generated power _P1 ^* that the first generated power _P1 should follow is changed by a first interval _Pwidth1 at least once. In the second and fourth processes, the command charge/discharge power _Pstorage ^* that the charge/discharge power _Pstorage should follow is changed by a second interval _Pwidth2 at least once.

The first step width _Pwidth1 and the second step width _Pwidth2 can be set so as to ensure both the responsiveness and stability of the control. Typically, the first step width _Pwidth1 and the second step width _Pwidth2 are very small.

5, when the command first generated power _P1 ^* reaches the lower limit power _Pmin by the first process, the second process is started. When the command first generated power _P1 ^* reaches the upper limit power _Pmax by the third process, the fourth process is started. By setting the lower limit power _Pmin and the upper limit power _Pmax suitable for the first power generating device 3, the adjustment of the power received from the commercial power source 5B by adjusting the first generated power _P1 can be performed within a reasonable range for the first power generating device 3.

In the example of Fig. 5, the first and third processes are performed while maintaining the command charge/discharge power _Pstorage ^* at the current value. The second process is performed while maintaining the command first power generation power _P1 ^* at the lower limit power _Pmin . The fourth process is performed while maintaining the command first power generation power _P1 ^* at the upper limit power _Pmax .

The first process and the third process may be performed while maintaining the command charge/discharge power P _storage ^* at zero. This is suitable for suppressing the charge/discharge of the power storage device 9.

The upper limit power _Pmax is, for example, the maximum value of the first generated power _P1 that can currently be output by the first power generation device 3. The lower limit power _Pmin is set, for example, to a value that ensures power generation efficiency in the first power generation device 3.

The upper limit power _Pmax and the lower limit power _Pmin may be changed during operation of the distributed power system 1. For example, when the first power generating device 3 is the Rankine cycle power generating device shown in FIG. 2A and FIG. 2B, the first generated power _P1 that the first power generating device 3 can output varies depending on the temperature, flow rate, etc. of the heating medium supplied to the evaporator 3B. In consideration of this, it is reasonable to change the upper limit power _Pmax and the lower limit power _Pmin according to the temperature, flow rate, etc. of the heating medium. The temperature, flow rate, etc. of the heating medium can be reflected in the detected temperature of the temperature sensor 3D. Therefore, in one example of this embodiment, the control device 8 changes the upper limit power _Pmax and the lower limit power _Pmin based on the detected temperature of the temperature sensor 3D.

The upper limit power P _max and the lower limit power P _min may be maintained constant during operation of the distributed power system 1 .

As can be seen from Fig. 5, the operation modes executed by the control device 8 include a first mode in which one of a plurality of processes including a first process, a second process, a third process, and a fourth process is selected and executed. The first generated power _P1 at the start of the first mode may be greater than zero and less than the rated value of the first generated power _P1 . In this way, it is easy to continue the state in which the first generated power can be increased or decreased after the start of the first mode. This is suitable for suppressing the charging and discharging of the storage device 9. According to an operation in which charging and discharging can be easily suppressed, it is possible to use an inexpensive storage device 9 with a limited capacity.

The first generated power _P1 at the start of the first mode may be a value within a range of 20% to 80% of the rated value of the first generated power _P1 , or may be a value within a range of 40% to 60% of the rated value.

The command first power generation power _P1 ^* at the start of the first mode may be a value greater than zero and less than the rated value of the first power generation power _P1 , or may be a value within the range of 20% to 80% of the rated value, or may be a value within the range of 40% to 60% of the rated value.

The command first power generation power _P1 ^* at the start of the first mode may be a value greater than the lower limit power _Pmin and smaller than the upper limit power _Pmax , or may be a value obtained by adding a value within a range from ₂₀ % to 80% of the range between the upper limit power _Pmax and the lower limit power _Pmin to the lower limit power Pmin, or may be a value obtained by adding a value within a range from 40% to 60% of that range to the lower limit power _Pmin .

Typically, after several days have passed since the start of the first mode, a periodicity appears in the daily change of the first generated power _P1 . In one specific example, in the first mode, after two or more days have passed since the start of the first mode, a transition of the first generated power _P1 in which the first generated power _P1 increases across the reference power and the first generated power _P1 decreases across the reference power appears repeatedly over multiple days. Here, the reference power is a power that is greater than zero and smaller than the rated value of the first generated power. The reference power may be a value within a range of 20% to 80% of the rated value, or may be a value within a range of 40% to 60% of the rated value.

In this embodiment, the total generated power _Psum is the sum of the generated power _P1 of the first power generating device 3 and the generated power _P2 of the second power generating device 2. Therefore, in the first mode, when the second generated power _P2 increases, the first generated power _P1 can be reduced. Also, when the second generated power _P2 decreases, the first generated power _P1 can be increased. In this way, in this embodiment, the generated power _P1 can be controlled complementarily with the generated power _P2 .

When the second power generating device 2 is a photovoltaic power generating device, the power generation power _P2 of the second power generating device 2 fluctuates depending on the weather. However, according to the present embodiment, when the power generation power _P2 fluctuates in this way, the first power generation power _P1 can be controlled so that the fluctuation of the total power generation power _Psum is suppressed. Typically, the responsiveness of the control of the power generation power _P1 of the first power generating device 3 is higher than the responsiveness of the control of the power generation power of a thermal power plant owned by a power company. In one specific example, even in a situation where the power generation power _P2 decreases for a short period of time due to clouds passing across the sun, the first power generation power _P1 can be controlled with high responsiveness, and the fluctuation of the total power generation power _Psum can be suppressed. This is advantageous from the viewpoint of stabilizing the specific power _Pgrid .

If the differential power P _delta does not become zero even when the first process to the fourth process are performed, the differential power P _delta may be brought closer to zero by adjusting the second generated power _P2 of the second power generation device 2. For example, when the second power generation device 2 is a solar power generation device, if the differential power P _delta does not become zero even when the first process and the second process are performed, the differential power P _delta may be brought closer to zero by reducing the second generated power _P2 .

In one example, the first step width _Pwidth1 and the second step width _Pwidth2 are fixed values, which makes it easier to stabilize the control.

In another example, the first step width P _width1 and the second step width P _width2 are changed according to the magnitude of P _delta . Specifically, the larger P _delta is, the larger the first step width P _width1 and the second step width P _width2 can be. In this way, it is possible to achieve both stability and responsiveness of the control. Specifically, it is possible to reduce the number of control cycles that are repeated until the generated power P ₁ and the charge/discharge power P _storage converge while ensuring the stability of the control. This allows the generated power P ₁ and the charge/discharge power P _storage to converge in a short time. This is advantageous from the viewpoint of stabilizing the specific power P _grid .

One of the first step size _Pwidth1 and the second step size _Pwidth2 may be changed according to the magnitude of _Pdelta . Specifically, the larger _Pdelta is, the larger one of the first step size _Pwidth1 and the second step size _Pwidth2 may be made.

Below, the relationship between the generated power in the distributed power system 1, the received power from the commercial power source 5A, and the required power of the load 5B will be explained with reference to Figures 6A to 6E.

Figure 6A shows a specific example of this embodiment. In the specific example of Figure 6A, the multiple power generation devices 32 are two power generation devices, a first power generation device 3 and a second power generation device 2. The first power generation device 3 is an exhaust heat power generation device that generates power by utilizing exhaust heat. The second power generation device 2 is a solar power generation device. The storage battery 9A is a storage battery.

In the following description, the power generated by the first power generating device 3 may be referred to as exhaust heat power. The power generated by the second power generating device 2 may be referred to as photovoltaic power. The power required by the load 5B may be referred to as load power. The power received by the load 5B from the commercial power source 5A may be simply referred to as received power. As described above, a value that indicates the charging power of the storage battery 9A when it is positive and indicates the discharging power of the storage battery 9A when its absolute value is negative may be referred to as charging/discharging power. The power output from the power output unit 6о of the power output device 6 may be simply referred to as output power.

The comparative example in FIG. 6B differs from the example in FIG. 6A in that it does not have a storage battery. In FIG. 6B, the sum of the exhaust heat power generation power and the solar power generation power is smaller than the load power at any time. During the daytime, the solar power generation power is large, the sum of the exhaust heat power generation power and the solar power generation power is maximum, this sum is closest to the load power, and the received power is minimum. On the other hand, during the nighttime, the solar power generation power is zero, and the received power is maximum when the load power is maximum. In the comparative example in FIG. 6B, the deviation between the maximum and minimum values of the received power in one day is large.

The comparative example in FIG. 6C differs from the comparative example in FIG. 6B in that it does not have an exhaust heat power generation device. Furthermore, the comparative example in FIG. 6C has a higher solar power generation power than the comparative example in FIG. 6B. In the comparative example in FIG. 6C, like the comparative example in FIG. 6B, the received power is minimum during daytime hours. During nighttime hours, the received power is maximum when the load power is maximum. In the comparative example in FIG. 6C, the maximum value of the received power is larger and the deviation between the maximum and minimum values of the received power in one day is larger than in the comparative example in FIG. 6B.

In the comparative example of FIG. 6D, the photovoltaic power generation is greater than in the comparative example of FIG. 6C. Specifically, in the comparative example of FIG. 6D, it is assumed that the photovoltaic power generation is obtained so that the amount of power generated in one day by the photovoltaic power generation device is the same as the total amount of power generated in one day by the exhaust heat power generation device and the photovoltaic power generation device in the comparative example of FIG. 6B. In the comparative example of FIG. 6D, the maximum value of the photovoltaic power generation is large. At a certain time during the daytime when this maximum value appears, this maximum value is greater than the received power. Therefore, at this time, the received power is negative, that is, a reverse power flow occurs from the distributed power system to the commercial power source. Also, in the comparative example of FIG. 6D, the photovoltaic power generation is zero during the nighttime, and the load power is at a maximum. In the comparative example of FIG. 6D, the deviation between the maximum value and the minimum value of the received power in one day is greater than in the comparative example of FIG. 6C.

The comparative example in FIG. 6E differs from the example in FIG. 6A in that there is no exhaust heat power generation device and that, like the comparative example in FIG. 6D, the solar power generation power is large. In the comparative example in FIG. 6E, charging and discharging are performed by the storage battery, and no reverse power flow occurs. Also, in the comparative example in FIG. 6E, unlike the comparative examples in FIG. 6B to FIG. 6D, the received power is substantially constant over one day. However, the solar power generation power is zero during the nighttime hours and is large during the daytime hours. For this reason, the charging and discharging power of the storage battery and the amount of power stored in the storage battery can be large. For this reason, the comparative example in FIG. 6E requires a large-capacity storage battery.

In contrast, the specific example of this embodiment shown in FIG. 6A combines an exhaust heat power generation device 3, a solar power generation device 2, and a storage battery 9A. In addition, in this specific example, the control described using the flowchart in FIG. 5 is performed. As a result, the charging and discharging power of the storage battery 9A and the amount of power stored in the storage battery 9A can be suppressed. Therefore, in this specific example, the received power can be kept substantially constant over one day while using the small-capacity storage battery 9A.

It is not essential that _Pgrid follow a constant target power. Even in such a case, the above control can be said to suppress fluctuations in _Pgrid and stabilize the power supplied from the commercial power source to the load.
A plurality of power generation units 32 including a first power generation unit 3;
A power storage device 9 connected to a plurality of power generation devices 32;
a power output device 6 including a power input unit 6i connected to a plurality of power generation devices 32 and a power storage device 9, and a power output unit 6o connected to a commercial power source 5A via a branch unit BP connected to a load 5B;
A detection device 71 or 81;
A control device 8,
When a value representing the power received from the commercial power source 5A and identified using the detection device 71 or 81 is defined as a specific power _Pgrid , the power generated by the first power generation device 3 is defined as a first generated power _P1 , and a value indicating the charging power of the power storage device 9 when it is positive and indicating the discharge power of the power storage device 9 when its absolute value is negative is defined as a charging/discharging power _Pstorage of the power storage device 9, the control device 8:
Calculate a differential power P _delta by subtracting the specific power P _grid from the target power P _grid ^* ;
When the differential power P _delta is greater than zero, in the case where the second process for increasing the charge/discharge power P _storage is executed, the first generated power P ₁ is decreased before the second process is executed.
Execute the process,
When the differential power P _delta is smaller than zero, in the case where the fourth process for decreasing the charge/discharge power P _storage is executed, the third process for increasing the first generated power P ₁ is executed before the fourth process is executed.
Execute the process,
It can also be thought that the present invention provides a distributed power system 1. Such a distributed power system can be an inexpensive system suitable for stabilizing the power supplied from a commercial power source to a load.

Similarly, the present disclosure provides
A plurality of power generation units 32 including a first power generation unit 3;
A power storage device 9 connected to a plurality of power generation devices 32;
a power output device 6 including a power input unit 6i connected to a plurality of power generation devices 32 and a power storage device 9, and a power output unit 6o connected to a commercial power source 5A via a branch unit BP connected to a load 5B;
A control device 8 for controlling a distributed power system 1 including a detection device 71 or 81,
When a value representing the power received from the commercial power source 5A and identified using the detection device 71 or 81 is defined as a specific power _Pgrid , the power generated by the first power generation device 3 is defined as a first generated power _P1 , and a value indicating the charging power of the power storage device 9 when it is positive and indicating the discharge power of the power storage device 9 when its absolute value is negative is defined as a charging/discharging power _Pstorage of the power storage device 9, the control device 8:
Calculate a differential power P _delta by subtracting the specific power P _grid from the target power P _grid ^* ;
When the differential power P _delta is greater than zero, in the case where the second process for increasing the charge/discharge power P _storage is executed, the first generated power P ₁ is decreased before the second process is executed.
Execute the process,
When the differential power P _delta is smaller than zero, in the case where the fourth process for decreasing the charge/discharge power P _storage is executed, the third process for increasing the first generated power P ₁ is executed before the fourth process is executed.
Execute the process,
It can also be thought of as providing a control device 8 .

Similarly, the present disclosure provides
A plurality of power generation units 32 including a first power generation unit 3;
A power storage device 9 connected to a plurality of power generation devices 32;
a power input unit 6i connected to a plurality of power generation devices 32 and a power storage device 9; and a power output unit 6o connected to a commercial power source 5A via a branch point BP connected to a load 5B;
A control method for controlling a distributed power system 1 including a power output device 6 including a detection device 71 or 81,
A value representing the power received from the commercial power source 5A and identified using the detection device 71 or 81 is defined as a specific power _Pgrid , the power generated by the first power generation device 3 is defined as a first generated power _P1 , and a value indicating the charging power of the storage device 9 when it is positive and indicating the discharge power of the storage device 9 when its absolute value is negative is defined as a charging/discharging power _Pstorage of the storage device 9,
Calculating a differential power P _delta by subtracting the specific power P _grid from the target power P _grid ^* ;
When the differential power P _delta is greater than zero, in the case where the second process for increasing the charge/discharge power P _storage is executed, the first generated power P ₁ is decreased before the second process is executed.
Performing a process; and
When the differential power P _delta is smaller than zero, in the case where the fourth process for decreasing the charge/discharge power P _storage is executed, the third process for increasing the first generated power P ₁ is executed before the fourth process is executed.
Performing a process; and
It can also be considered that the present invention provides a control method including the steps of:

The technology disclosed herein can stabilize the power generated by a power generation device that has power generation adjustment capability, the power generated by a power generation device that uses renewable energy, and the power received from a commercial power source using a small-capacity power storage device. Examples of power generation devices that have power generation adjustment capability include power generation devices that use exhaust heat and power generation devices that use fuel cells. Examples of power generation devices that use renewable energy include power generation devices that use solar power and power generation devices that use wind power.

1 Distributed power supply system 2, 3 Power generation device 2A, 3R Power generation source 2B, 3H, 9B Power converter 3A Pump 3B Evaporator 3C Expansion machine 3D Temperature sensor 3E Bypass valve 3F Condenser 3G Generator 5A Commercial power source 5B Load 6 Power output device 7, 71, 81 Detection device 7A, 71A, 81A Current detector 7B, 71B, 81B Voltage detector 7C, 71C, 81C Power calculation unit 8 Control device 9 Storage device 9A Storage machine 10, 11, 13, 16, 17, 18, 19, 20, 21 Switching element 12, 15 Reactor 14, 51, 52, 53, 54, 55, 56, 57, 58, 59 Diode 22, 41, 42, 46, 47 Capacitor 35, 36 Electric circuit 60 Switching circuit 61, 62, 63 Phase circuits 66, 67, 68 connection points

Claims (4)

A power generation device;
A power storage device;
A control device that executes at least one of a first control and a second control,
the power generation device, the power storage device, and a commercial power source are connected to each other;
the first control is a control in which, when the target power is greater than a power value received from the commercial power source, a charge/discharge power of the power storage device is increased, a power generation power of the power generation device is reduced before the charge/discharge power is increased;
The second control is a control in which, when the charge/discharge power is to be reduced when the target power is smaller than the power value, the power generation power of the power generation device is increased before the charge/discharge power is reduced.
Distributed power systems. A power generation device;
A power storage device,
A control device for controlling a distributed power supply system in which the power generation device, the power storage device, and a commercial power supply are connected to each other,
The control device executes at least one of a first control and a second control,
the first control is a control in which, when the target power is greater than a power value received from the commercial power source, a charge/discharge power of the power storage device is increased, the power generation power of the power generation device is reduced before the charge/discharge power is increased;
The second control is a control in which, when the charge/discharge power is to be reduced when the target power is smaller than the power value, the power generation power of the power generation device is increased before the charge/discharge power is reduced.
Control device. A power generation device;
A power storage device,
A control method for controlling a distributed power supply system in which the power generation device, the power storage device, and a commercial power supply are connected to each other, comprising:
A control method comprising: when increasing the charging/discharging power of the power storage device when the target power is greater than the power value received from the commercial power source, reducing the generated power of the power generation device before increasing the charging/discharging power. A power generation device;
A power storage device,
A control method for controlling a distributed power supply system in which the power generation device, the power storage device, and a commercial power supply are connected to each other, comprising:
A control method including, when reducing the charging/discharging power of the power storage device when the target power is smaller than the power value received from the commercial power source, increasing the generated power of the power generation device before reducing the charging/discharging power.

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