JP7679272B2 - power supply equipment - Google Patents

Description

The present invention relates to a power supply system that stably supplies power generated by a renewable energy power generation device to a load.

Patent Document 1 is known as a power supply facility that stably supplies the generated power of a renewable energy power generation device to a load. Patent Document 1 describes a power control device that includes a control unit configured to be able to control a bidirectional inverter connected between an AC side and a DC side, and the control unit acquires predicted values for the amount of generated power of the renewable energy power generation device and the amount of consumed power of the load at a plurality of times between a first time and a second time, assumes a target charge amount of the power storage device at the second time, and updates the target charge amount at each time by applying the predicted values at each time going back from the second time to the first time to the assumed target charge amount. Based on the target charge amount at the first time, the control unit causes the bidirectional inverter to perform a charge operation or a discharge operation.

JP 2021-52488 A

According to Patent Document 1, the storage battery can be effectively utilized by having the bidirectional inverter perform charging or discharging operations based on the target charge amount of the power storage device, which is assumed from the predicted values of the amount of power generated by the renewable energy power generation device and the amount of power consumed by the load. However, there is an issue that when the predicted value and the actual power deviate due to a sudden change in the generated power caused by a change in weather or a sudden change in the load, the voltage value of the DC connection part may deviate from a specified value or a specified range.

The voltage value of the DC connection may deviate from a specified value or range, and deviation of the voltage value from the specified range may cause failure of equipment connected to the DC power line.

In view of this problem, the present invention aims to provide a power supply facility in which each DC device in the power supply facility stably supplies DC power.

In view of the above, the present invention provides a power supply facility including a first conversion device arranged between an AC power line and a DC power line to perform power conversion, a second conversion device arranged between the DC power line and a storage battery to perform power conversion, and a third conversion device arranged between the DC power line and a renewable energy power source to perform power conversion, the first conversion device controls the voltage of the DC power line to a first voltage, and the second conversion device controls the voltage of the DC power line to a second voltage when the first conversion device cannot control the voltage of the DC power line to the first voltage and the voltage of the DC power line exceeds a second voltage set higher than the first voltage, and the first conversion device and the third conversion device convert a fourth voltage into a fourth voltage on the first DC power line. a first end of the fourth conversion device connected to the first converter and a second end of the fourth conversion device connected to the second conversion device via a first DC power line, the fourth conversion device controls a ratio of a voltage of the first DC power line to a voltage of a second DC power line to a constant value, the first conversion device controls the voltage of the first DC power line to a voltage value obtained by multiplying the first voltage by the constant value, and the second conversion device controls the voltage of the second DC power line to the second voltage when the first conversion device cannot control the voltage of the first DC power line to a voltage value obtained by multiplying the first voltage by the constant value and the voltage of the second DC power line exceeds the second voltage .

According to the present invention, each DC device in the power supply facility can actively switch control by referring to the voltage value of the DC power line without using external commands, thereby enabling a stable supply of DC power.

1 is a diagram showing a configuration example of a power supply facility according to a first embodiment of the present invention; FIG. 2 is a diagram showing a first example of control of the power of each component and the voltage VD of a DC power line when the present invention is applied. FIG. 11 is a diagram showing a second example of control of the power of each component and the voltage VD of a DC power line when the present invention is applied. FIG. 11 is a diagram showing a third example of control of the power of each component and the voltage VD of a DC power line when the present invention is applied. FIG. 11 is a diagram showing a fourth example of control of the power of each component and the voltage VD of the DC power line when the present invention is applied. FIG. 11 is a diagram showing a fifth example of control of the power of each component and the voltage VD of a DC power line when the present invention is applied. FIG. 4 is a diagram showing another configuration example of the power supply facility according to the first embodiment of the present invention. FIG. 4 is a diagram showing yet another configuration example of the power supply facility according to the first embodiment of the present invention. FIG. 11 is a diagram showing a configuration example of a power supply facility according to a second embodiment of the present invention. FIG. 13 is a diagram showing an example of control of the power of each component and the voltage VD of a DC power line when the second embodiment of the present invention is applied. FIG. 11 is a diagram showing a configuration example of a power supply facility according to a third embodiment of the present invention. FIG. 13 is a diagram showing an example of control of the power of each component and the voltage VD of a DC power line when the third embodiment of the present invention is applied. FIG. 13 is a diagram showing a configuration example of a power supply facility according to a fourth embodiment of the present invention. FIG. 13 is a diagram showing a configuration example of a power supply facility according to a fifth embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. Note that the present invention is not limited to the following embodiment. Those skilled in the art can make various additions and modifications within the scope of the present invention.

Figure 1 shows an example of the configuration of a power supply facility according to a first embodiment of the present invention. The power supply facility 1 includes a solar cell 2, a first DC/DC converter 3, a power storage device 4, an AC/DC inverter 5, a DC power line 6, and a power supply facility control unit 7. The solar cell 2 is connected to the first DC/DC converter 3. The DC power line 6 connects the output terminal of the first DC/DC converter 3, the power storage device 4, and the DC output terminal of the AC/DC inverter 5 in parallel. The AC output terminal of the AC/DC inverter 5 is connected to a distribution line 8 connected to an AC power source 9, and the AC/DC inverter 5 is capable of bidirectional power conversion. An AC load 10 is connected to the distribution line 8.

The power storage device 4 is composed of a storage battery 41 and a DC/DC converter 42. The DC/DC converter 42 is a bidirectional power conversion circuit, and the storage battery 41 can be charged and discharged by the control of the DC/DC converter 42. The storage battery 41 is, for example, a secondary battery such as a lithium-ion battery or a nickel-metal hydride battery. The power storage device 4 may be a stationary facility, or the storage battery 41 may be an electrically-driven mobile object such as an electric vehicle, and the DC/DC converter 42 may be a stationary charger/discharger.

In the power supply facility 1 in FIG. 1, the solar cell 2 may generally be a renewable energy power source such as photovoltaic power generation or wind power generation, and here, the case of photovoltaic power generation is shown. In the case of wind power generation, the wind power generation itself outputs AC, so the first DC/DC converter 3 is configured as an inverter that converts AC to DC. Although there are differences in the configuration, the present invention can be applied to any of the above renewable energy power sources.

As shown in FIG. 1, the power supply facility 1 is composed of a first conversion device (AC/DC inverter 5) that is arranged between the AC power line 8 and the DC power line 6 and performs power conversion, a second conversion device (DC/DC converter 42) that is arranged between the DC power line 6 and the storage battery 4 and performs power conversion, and a third conversion device (first DC/DC converter 3) that is arranged between the DC power line 6 and the renewable energy power source 2 and performs power conversion.

In the present invention, the power supply equipment 1 has two types of control functions: the power supply equipment control unit 7 and control by voltage adjustment units 5V, 3V, 4V arranged for each individual conversion device 3, 42, 5. The voltage adjustment units 5V, 3V, 4V may have their functions in the control circuits (not shown) that the conversion devices 3, 42, 5 each have. As will be described in detail later, the power supply equipment control unit 7 performs long-term control on the three sets of conversion devices 3, 42, 5 described above on a scale of several seconds or minutes, while the control by the voltage adjustment units 5V, 3V, 4V arranged for each individual conversion device 3, 42, 5 performs short-term control. The short-term control is performed in a shorter cycle than the long-term control.

The power supply equipment control unit 7 operates as an EMS (Energy Management System). That is, it measures (not shown) the power received from the AC power source 9, the power consumption of the load 10, the power generated by the solar cell 2, the SOC (State of Charge) of the storage battery 41, etc., and determines the power flow within the power supply equipment 1 from the viewpoints of the rated power of each device, the predicted power generation of the solar cell 2, the predicted power consumption of the load 10, the SOC of the storage battery 41, life and deterioration management, etc.

Then, it issues control commands to the storage device 4, such as a charge/discharge power command or a charge/discharge current command, upper and lower charge/discharge power limits or upper and lower charge/discharge current limits, and upper and lower SOC limits, and issues control commands to the AC/DC inverter 5, such as upper and lower conversion power limits. The commands are issued at regular intervals (e.g., one minute intervals) via wired or wireless communication. The power supply equipment control unit 7 also issues control commands to the first DC/DC converter 3, the storage device 4, and the AC/DC inverter 5 to start and stop operation.

The power supply equipment control unit 7 issues these commands to the first DC/DC converter 3, the power storage device 4, and the AC/DC inverter 5 over a long period of time, on the order of tens of seconds or even minutes.

The first DC/DC converter 3 performs maximum power point tracking (MPPT) control of the generated power output by the connected solar cell 2, and outputs it to the DC power line 6. The power storage device 4 also performs charge/discharge power or charge/discharge current control according to commands from the power supply equipment control unit 7.

In contrast to this, the other control system, which is control by voltage adjustment units 5V, 3V, 4V arranged for each individual conversion device 3, 42, 5, detects the voltage VD of the DC power line 6 and controls it to the respective set voltage values VD1, VD2 or VD4, VD3. The voltage adjustment unit 5V of the AC/DC inverter 5 is set to the voltage value VD1, the voltage adjustment unit 4V of the DC/DC converter 42 is set to the voltage values VD2 and VD4, and the voltage adjustment unit 3V of the first DC/DC converter 3 is set to the voltage value VD3.

At this time, the magnitude relationship of each voltage value is voltage value VD3>voltage value VD2>voltage value VD1, and normally the voltage VD of the DC power line 6 is controlled to the voltage value VD1 by the voltage adjustment unit 5V of the AC/DC inverter 5, but when the voltage VD of the DC power line 6 rises, it is controlled to the voltage value VD2 by the voltage adjustment unit 4V of the DC/DC converter 42, and when the voltage VD of the DC power line 6 rises further, it is controlled to the voltage value VD3 by the voltage adjustment unit 3V of the first DC/DC converter 3. The voltage value VD4 will be described later.

Note that although it may not be possible to control the voltage to the target value VD, the voltage control itself continues. The AC/DC inverter 5 always attempts to control to VD1, but the upper limit of the conversion power is reached, and as a result, P3+P4>P5 occurs, and the voltage rises without being controlled to VD1. At that time, the storage device starts voltage control to VD2, but the AC/DC inverter 5 continues the control operation (control to VD1). The same is true for the storage device 4.

By applying the two types of control systems described above, the three sets of conversion devices 3, 42, and 5 will carry out voltage control of the DC power line 6 within the range of control commands regarding various long-term restrictions set by the power supply equipment control unit 7.

This sharing control is specifically executed as follows depending on the operating status of the power supply facility 1. First, the AC/DC inverter 5 controls the voltage VD of the DC power line 6 to a voltage value VD1. The voltage value VD1 is, for example, 350V. The AC/DC inverter 5 controls the AC output power P5 so that the voltage VD of the DC power line 6 is controlled to the voltage value VD1. At this time, the sum of the output power P3 of the first DC/DC converter 3 and the discharge power P4 of the storage device 4 is equal to the AC output power P5 of the AC/DC inverter 5 (P3 + P4 = P5). The first voltage VD1 is set from among the voltage ranges common to the input voltage ranges of the AC/DC inverter 5, the first DC/DC converter 3, and the storage device 4 connected to the DC voltage line 6, excluding the maximum and minimum values.

When the voltage VD of the DC power line 6 is higher than the voltage value VD1, the AC/DC inverter 5 outputs AC power to the distribution line 8 side to supply power to the load 10, thereby lowering the voltage VD of the DC power line 6 to the voltage value VD1. When the voltage VD of the DC power line 6 is lower than the voltage value VD1, the AC/DC inverter 5 receives power from the AC power source 9 from the distribution line 8 side and supplies the power to the power storage device 4, thereby raising the voltage VD of the DC power line 6 to the voltage value VD1.

As described above, the AC/DC inverter 5 can control the voltage VD of the DC power line 6 to a voltage value VD1 by controlling the converted power. In this embodiment, the power conversion from the DC side to the AC side is positive, and the power conversion from the AC side to the DC side is negative.

However, the power that the AC/DC inverter 5 can convert is limited by the rated power. In addition, when the power supply equipment control unit 7 is managing the reverse flow power and the received power to the AC power source 9, the AC/DC inverter 5 is commanded by the power supply equipment control unit 7 for the upper and lower conversion power limits. Therefore, the upper limit of the conversion power of the AC/DC inverter 5 is the minimum of the rated power of the AC/DC inverter 5 and the upper conversion power limit commanded by the power supply equipment control unit 7, and the lower limit of the conversion power of the AC/DC inverter 5 is the maximum of the rated power of the AC/DC inverter 5 x (-1) and the lower conversion power limit commanded by the power supply equipment control unit 7. Due to the upper and lower limits of the conversion power, there are cases where the AC/DC inverter 5 cannot control the voltage VD of the DC power line 6 to the voltage value VD1.

Figure 2 shows a first control example of the power of each part and the voltage VD of the DC power line when the present invention is applied. First, the output power P3 of the first DC/DC converter 3, the discharge power P4 of the storage device 4, and the AC output power P5 of the AC/DC inverter 5 are shown at the top of Figure 2 as the power of each part of the power supply facility 1. However, here, the converted power P5 of the AC/DC inverter 5 is positive when output to the AC side, and negative when input (received power) from the AC side. Also, the charge/discharge power P4 of the storage device 4 is positive when discharged, and negative when charged. The output P3 of the first DC/DC converter 3 is positive.

The lower part of Figure 2 shows the relationship between the time change of the DC power line voltage VD and the voltage values VD1, VD2, and VD3 set for each of the three sets.

According to the time notation shown on the horizontal axis at the top of Figure 2, the control period of the power supply equipment control unit 7 is T, which indicates that after a command is given at time 0, a command is given again at time T. In contrast, times T1 to T6 shown within the period T are the times when various events occur in the three sets of conversion devices 3, 42, and 5 in the power supply equipment 1, and as is clear from this, the control of the power supply equipment 1 is long-period control, while the control by the voltage adjustment units 5V, 3V, and 4V arranged for each individual conversion device 3, 42, and 5 can be said to be short-period control.

In the two-system control shown in FIG. 1, the long-period control power supply equipment control unit 7 provides upper and lower limit values to the converters 42 and 5, and the converters 42 and 5 are operated within the given limits. However, for renewable energy sources, it is best to prioritize outputting the amount of power generated as is and not impose special restrictions.

In the illustrated example, at time 0, the power supply equipment control unit 7 commands the AC/DC inverter 5 to set its upper conversion power limit to 50 kW (the conversion power P5 is 40 kW at time 0), and the storage device 4 has its charge/discharge power upper limit set to 20 kW and its charge/discharge power lower limit set to -20 kW. However, in the illustrated example, the storage device 4 is discharging at 20 kW to supply power to the load 10. Also, the output of the first DC/DC converter 3 at time 0 is 20 kW.

At this time, the sum of the output P3 (20 kW) of the first DC/DC converter 3 and the discharge power P4 (20 kW) of the storage device 4 is 40 kW, which is less than the upper limit of the conversion power P5 of the AC/DC inverter 5. Therefore, the AC/DC inverter 5 can control the voltage VD of the DC power line 6 to the voltage value VD1 by converting only 40 kW.

When the output power of the first DC/DC converter 3 increases due to fluctuations in solar radiation from time 0 to time T1, the AC/DC inverter 5 increases the conversion power P5 to control the voltage VD of the DC power line 6 to the first voltage VD1. At time T1, the output power P3 of the first DC/DC converter 3 becomes 30 kW, and the conversion power P5 of the AC/DC inverter 5 reaches the upper limit value of 50 kW.

After time T1, when the output power P3 of the first DC/DC converter 3 increases further, the AC/DC inverter 5 cannot increase the converted power P5 from 50 kW, and the voltage VD of the DC power line 6 rises from the first voltage VD1. Then, at time T2, it reaches the second voltage VD2 (e.g., 370 V) that is higher than the first voltage VD1 and lower than the third voltage VD3.

When the voltage VD of the DC power line 6 is equal to or higher than the second voltage VD2, this state is detected by the voltage adjustment unit 4V of the DC/DC converter 42, and the storage device 4 stops the charge/discharge power control commanded by the power supply equipment control unit 7 and executes voltage control of the DC power line 6. The voltage control is performed, for example, by feedback control using the voltage VD of the DC power line 6 as a reference value.

At this time, in this embodiment, the storage device 4 executes voltage control with the second voltage VD2 as the target value. The storage device 4 also executes voltage control within a control range that maintains a discharge power equal to or greater than the charge/discharge power lower limit or a discharge current equal to or greater than the charge/discharge current lower limit commanded by the power supply equipment control unit 7. In this embodiment, it is assumed that -20 kW is commanded as the charge/discharge power lower limit. The upper limit of the discharge power or discharge current is the minimum value between the commanded charge/discharge power upper limit and 0 kW, or the minimum value between the commanded charge/discharge current upper limit and 0 A.

In addition, voltage control is performed only when the SOC of the storage battery 41 is below the SOC upper limit commanded by the power supply equipment control unit 7. This operation prevents overvoltage from being applied to the equipment connected to the DC power line 6. After time T2, the storage device 4 performs voltage control with the second voltage as a target value by reducing the discharge power and increasing the charge power.

At time T3, the discharge power of the storage device 4 reaches -20 kW (charging power 20 kW). After time T3, even if the output power P3 of the first DC/DC converter 3 increases further, the storage device 4 cannot increase the charging power, so the voltage VD of the DC power line 6 rises further from the second voltage VD2, and at time T4, it reaches a third voltage VD3 (e.g., 390 V) that is higher than the second voltage VD2 and lower than the maximum DC voltage. The maximum DC voltage is the input voltage upper limit value of the device with the lowest withstand voltage among the AC/DC inverter 5, the first DC/DC converter 3, and the storage device 4 connected to the DC voltage line 6.

As shown in the lower part of FIG. 2, in the above operation, the relationship between the second voltage VD2 and the third voltage VD3 is set so that the third voltage VD3 is higher than the second voltage VD2. This means that the control switching of the first DC/DC converter 3 is performed after the control switching of the storage device 4. With this setting, the first DC/DC converter 3 switches from MPPT control to voltage control, which results in the suppression of solar power generation, as a last resort, and power generation by the solar cell 2 can be continued as long as possible.

If the magnitude relationship of these voltages were reversed, and the second voltage VD2 were set higher than the third voltage VD3, and the third voltage VD3 was set higher than the first voltage VD1, power generation by the solar cell 2 would be suppressed before the storage device 4 switches control to increase the charging power, resulting in a waste of the power generation capacity of the solar cell 2.

When the voltage VD of the DC power line 6 is equal to or higher than the third voltage VD3, this state is detected by the voltage adjustment unit 3V of the first DC/DC converter 3, and the first DC/DC converter 3 stops MPPT control and executes voltage control of the DC power line 6. At this time, in this embodiment, the first DC/DC converter 3 executes voltage control with the third voltage VD3 as a target value. When the voltage VD of the DC power line 6 is equal to or higher than the third voltage VD3, there is no load or storage battery that can consume or charge all the power generated by the solar cell, so it is necessary to suppress the power generated by the solar cell 2. By switching to the voltage control described above, the power generation of the solar cell 2 is suppressed, and overvoltage application to the equipment connected to the DC power line 6 is prevented.

After time T4, the amount of solar radiation decreases, and the power generated by the solar cell 2 decreases. At time T5, the voltage VD of the DC power line 6 drops below the third voltage VD3. At this time, the first DC/DC converter 3 ends the voltage control of the DC power line 6 and resumes MPPT control. The power storage device 4 continues to control the voltage VD of the DC power line 6 to the second voltage.

When the power generated by the solar cell 2 further decreases, at time T6, the voltage VD of the DC power line 6 drops below the second voltage VD2. At this time, the storage device 4 ends the voltage control of the DC power line 6 and resumes the charge/discharge power control commanded by the power supply equipment control unit 7. Then, the voltage VD of the DC power line 6 is controlled to the first voltage VD1 after time T7 by the voltage control of the AC/DC inverter.

At time T when a new command is received from the power supply equipment control unit 7, the voltage VD of the DC power line 6 is the first voltage VD1. At this time, the upper limit of the conversion power of the AC/DC inverter 5 is updated to the minimum value of the rated power of the AC/DC inverter 5 and the conversion power upper limit value received from the power supply equipment control unit 7 at time T. In addition, the lower limit of the conversion power of the AC/DC inverter 5 becomes the maximum value of the rated power of the AC/DC inverter 5 × (-1) and the conversion power lower limit value commanded from the power supply equipment control unit 7. The storage device 4 operates according to the charge/discharge power command or charge/discharge current command received from the power supply equipment control unit 7 at time T. In addition, the charge/discharge power upper and lower limit values or the charge/discharge current upper and lower limit values, and the SOC upper and lower limit values are updated. The power after time T in FIG. 2 shows a case where the upper limit of the conversion power of the AC/DC inverter 5 is updated to 50 kW and the storage device 4 discharges at the new charge/discharge power command value of 10 kW.

Figure 3 shows control example 2 of the power of each component and the voltage VD of the DC power line when the present invention is applied. The explanation up to time T5 is omitted since it is the same as control example 1 shown in Figure 2. In Figure 3, at time T, the first DC/DC converter 3 executes MPPT control, and the storage device 4 controls the voltage VD of the DC power line 6 to the second voltage. In this example, the storage device 4 is operating with a discharge power of 5 kW.

When time T arrives when the voltage VD of the DC power line 6 is equal to or greater than the second voltage VD2 and less than the third voltage VD3, and the AC/DC inverter 5 and the power storage device 4 receive a new command from the power supply equipment control unit 7, the upper limit of the conversion power of the AC/DC inverter 5 is updated to the minimum of the rated power of the AC/DC inverter 5 and the upper limit of the conversion power received from the power supply equipment control unit 7 at time T, as explained in FIG. 2. In FIG. 3, it is assumed that the upper limit of the conversion power of the AC/DC inverter 5 is updated to 50 kW at time T.

The storage device 4 updates the upper and lower limit values of the charge and discharge power or the upper and lower limit values of the charge and discharge current, and the upper and lower limit values of the SOC to new values received from the power supply equipment control unit 7. The storage device 4 also compares the charge and discharge power command or the charge and discharge current command (called the command value in this embodiment) received from the power supply equipment control unit 7 at time T with the actual charge and discharge power or the charge and discharge current (called the actual value in this embodiment) at time T, assuming that the power and current in the discharging direction are positive. If the command value is smaller than the actual value, the storage device 4 ends the voltage control of the DC power line 6 and performs the charge and discharge power control according to the command value. If the command value is larger than the actual value, the voltage control of the DC power line 6 is continued. However, the command value received at time T is held, and the storage device 4 ends the voltage control of the DC power line 6 and is used as the command value from the power supply equipment control unit 7 when the storage device 4 ends the voltage control of the DC power line 6 and resumes the charge and discharge power control.

In Figure 3, the discharge power of the storage device 4 immediately before time T is 5 kW. When the storage device 4 receives a charge/discharge power command to discharge -10 kW (charge 10 kW) from the power supply equipment control unit 7 at time T, since the command value of -10 kW is smaller than the actual value of 5 kW, the storage device 4 ends the voltage control of the DC power line 6 and performs discharge power control according to the command value of -10 kW. At this time, the voltage VD of the DC power line 6 is controlled to the first voltage VD1 by the voltage control of the AC/DC inverter.

Figure 4 shows control example 3 of the power of each component and the voltage VD of the DC power line when the present invention is applied. The explanation up to time T4 is omitted since it is the same as control example 1 shown in Figure 2. In Figure 4, at time T, the first DC/DC converter 3 controls the voltage VD of the DC power line 6 to a third voltage VD3. The storage device 4 is assumed to be operating with a discharge power of -20 kW (charge power of 20 kW).

When the voltage VD of the DC power line 6 is equal to or higher than the third voltage VD3 and the AC/DC inverter 5 and the power storage device 4 receive a new command from the power supply equipment control unit 7 at time T, the upper limit of the conversion power of the AC/DC inverter 5 is updated to the minimum of the rated power of the AC/DC inverter 5 and the upper limit of the conversion power received from the power supply equipment control unit 7 at time T, as explained in FIG. 2.

The power storage device 4 updates the upper and lower charge/discharge power limits, or the upper and lower charge/discharge current limits, and the upper and lower SOC limits to new commands received from the power supply equipment control unit 7. The power storage device 4 also holds the charge/discharge power command or charge/discharge current command received from the power supply equipment control unit 7 at time T and continues voltage control of the DC power line 6. The held command value is used as the command value from the power supply equipment control unit 7 when the power storage device 4 ends voltage control of the DC power line 6 and resumes charge/discharge power control.

At time T, it is assumed that the upper limit of the conversion power of the AC/DC inverter 5 is updated to 50 kW, and the upper and lower limit values of the charge/discharge power of the power storage device 4 are updated to an upper limit of 20 kW and a lower limit of -40 kW. In addition, the charge/discharge power command of the power storage device 4 is -20 kW. At this time, the voltage VD of the DC power line 6 is the third voltage VD3, so that the power storage device 4 continues to perform the voltage control of the DC power line 6. Before time T, the charge/discharge power lower limit value was -20 kW, but since the charge/discharge power lower limit value is updated to -40 kW at time T, the discharge power of the power storage device 4 decreases. With this operation, when the voltage VD of the DC power line 6 drops from the third voltage VD3 to the second voltage VD2 at time T7, the first DC/DC converter 3 ends the voltage control of the DC power line 6 and resumes the MPPT control. Then, the power storage device 4 continues to control the voltage VD of the DC power line 6 to the second voltage.
In addition to the above operations, a control operation can also be performed in which the magnitude relationship of the voltage values is set as voltage value VD3>voltage value VD1>voltage value VD2, and normally voltage VD of DC power line 6 is controlled to voltage value VD2 by control by voltage adjustment unit 4V of DC/DC converter 42, but when voltage VD of DC power line 6 rises, it is controlled to voltage value VD1 by control by voltage adjustment unit 5V of AC/DC inverter 5, and when voltage VD of DC power line 6 further rises, it is controlled to voltage value VD3 by control by voltage adjustment unit 3V of first DC/DC converter 3. In this operation, power supply facility control unit 7 commands AC output power to AC/DC inverter 5, and when voltage VD of DC power line 6 is less than voltage value VD1, AC/DC inverter 5 outputs AC output power P5 to AC power line 8 in accordance with the command. However, if voltage adjustment unit 4V of DC/DC converter 42 cannot control voltage VD of DC power line 6 to voltage value VD2 and voltage VD rises to exceed voltage value VD1, voltage adjustment unit 5V of AC/DC inverter 5 controls voltage VD to voltage value VD1. At this time, AC/DC inverter 5 determines AC output power P5 within the range of upper and lower limit values of conversion power commanded by power supply equipment control unit 7. With this operation, power supply equipment 1 can be configured that commands and controls output power P5 to AC power line 8.

Figure 5 shows a fourth control example of the power of each part and the voltage VD of the DC power line when the present invention is applied. Figures 2, 3, and 4 show the response when the voltage VD of the DC power line rises, while Figures 5 and 6 show the response when the voltage VD of the DC power line falls.

In the example of FIG. 5, at time 0, the lower limit of the conversion power of the AC/DC inverter 5 is set to -50 kW, and the upper limit of the charge/discharge power of the storage device 4 is set to 60 kW, and the lower limit of the charge/discharge power of the storage device 4 is set to -60 kW. In addition, the storage device 4 is discharged at -60 kW by command of the power supply equipment control unit 7. In addition, the output of the first DC/DC converter 3 is 20 kW at time 0. At this time, the sum of the output of the first DC/DC converter 3 and the discharge power of the storage device 4 is -40 kW, which is above the lower limit of the conversion power of the AC/DC inverter 5. Therefore, the AC/DC inverter 5 converts power by -40 kW (receives only 40 kW from the distribution line 8), thereby controlling the voltage VD of the DC power line 6 to the first voltage VD1.

When the output power of the first DC/DC converter 3 decreases due to fluctuations in solar radiation from time 0 to time T1, the AC/DC inverter 5 reduces the conversion power to control the voltage VD of the DC power line 6 to the first voltage VD. At time T1, the output power of the first DC/DC converter 3 becomes 10 kW, and the conversion power of the AC/DC inverter 5 reaches the lower limit of -50 kW.

After time T1, when the output power of the first DC/DC converter 3 further decreases, the AC/DC inverter 5 cannot decrease the conversion power from -50 kW, and the voltage VD of the DC power line 6 decreases from the first voltage VD1. Then, at time T2, it reaches a fourth voltage VD4 (e.g., 340 V) that is lower than the first voltage VD1. The fourth voltage VD4 is set to a value higher than the minimum DC voltage of the power supply facility 1. The minimum DC voltage is set to a value (e.g., 320 V) higher than the maximum AC voltage (e.g., 220√2 V) at the AC output terminal of the AC/DC inverter 5. When the voltage VD of the DC power line 6 becomes equal to or lower than the minimum DC voltage, all the devices connected to the DC power line 6 (the first DC/DC converter 3, the storage device 4, and the AC/DC inverter 5) stop operating.

When the voltage VD of the DC power line 6 is equal to or lower than the fourth voltage VD4, the storage device 4 stops the charge/discharge power control instructed by the power supply equipment control unit 7 and executes the voltage control of the DC power line 6. In this embodiment, the storage device 4 executes voltage control with a discharge power less than the charge/discharge power upper limit or a discharge current less than the charge/discharge current upper limit, with the fourth voltage VD4 as the target value. Also, voltage control is executed only when the SOC of the storage battery 41 is equal to or higher than the SOC lower limit instructed by the power supply equipment control unit 7. This operation ensures the voltage required for the operation of the devices connected to the DC power line 6.

After time T2, the storage device 4 continues voltage control with the fourth voltage as the target value due to the increase in discharge power.

After time T3, when the output power of the first DC/DC converter 3 increases, the storage device 4 continues voltage control with the fourth voltage VD4 as the target value due to the decrease in discharge power. Then, when the output power of the first DC/DC converter 3 further increases, at time T4, the voltage VD of the DC power line 6 becomes equal to or higher than the fourth voltage VD4. At this time, the storage device 4 ends the voltage control of the DC power line 6 and resumes the charge/discharge power control commanded by the power supply equipment control unit 7. Then, the voltage VD of the DC power line 6 is controlled to the first voltage VD1 by the voltage control of the AC/DC inverter after time T5.

At time T when a new command is received from the power supply equipment control unit 7, the voltage VD of the DC power line 6 is the first voltage VD1. At this time, the upper limit of the conversion power of the AC/DC inverter 5 is updated to the minimum of the rated power of the AC/DC inverter 5 and the conversion power upper limit value received from the power supply equipment control unit 7 at time T. In addition, the lower limit of the conversion power of the AC/DC inverter 5 is updated to the maximum of the rated power of the AC/DC inverter 5 × (-1) and the conversion power lower limit value commanded from the power supply equipment control unit 7.

The energy storage device 4 operates according to the charge/discharge power command or charge/discharge current command received from the power supply equipment control unit 7 at time T. It also updates the upper and lower charge/discharge power limits or upper and lower charge/discharge current limits, and the upper and lower SOC limits. The power after time T in Figure 5 shows a case where the lower limit of the converted power of the AC/DC inverter 5 is updated to -50 kW, and the energy storage device 4 discharges at the new charge/discharge power command value of -50 kW.

Figure 6 shows control example 5 of the power of each component and the voltage VD of the DC power line when the present invention is applied. The explanation up to time T3 is omitted since it is the same as control example 4 shown in Figure 5. In Figure 6, at time T, the first DC/DC converter 3 executes MPPT control, and the storage device 4 controls the voltage VD of the DC power line 6 to a fourth voltage. In this embodiment, the storage device 4 is operating with a discharge power of -55 kW (charge power of 55 kW).

When time T arrives when the voltage VD of the DC power line 6 is equal to or greater than the fourth voltage VD4 and less than the first voltage VD1, and the AC/DC inverter 5 and the power storage device 4 receive a new command from the power supply equipment control unit 7, the upper limit of the conversion power of the AC/DC inverter 5 is updated to the minimum of the rated power of the AC/DC inverter 5 and the upper limit of the conversion power received from the power supply equipment control unit 7 at time T, as explained in FIG. 5. In addition, the lower limit of the conversion power of the AC/DC inverter 5 is updated to the maximum of the rated power of the AC/DC inverter 5 × (-1) and the lower limit of the conversion power commanded by the power supply equipment control unit 7.

The storage device 4 updates the upper and lower limit values of the charge and discharge power or the upper and lower limit values of the charge and discharge current, and the upper and lower limit values of the SOC to new values received from the power supply equipment control unit 7. The storage device 4 also compares the charge and discharge power command or the charge and discharge current command (called the command value in this embodiment) received from the power supply equipment control unit 7 at time T with the actual charge and discharge power or the charge and discharge current (called the actual value in this embodiment) at time T, assuming that the power and current in the discharging direction are positive. If the command value is larger than the actual value, the storage device 4 ends the voltage control of the DC power line 6 and performs the charge and discharge power control according to the command value. If the command value is smaller than the actual value, the voltage control of the DC power line 6 is continued. However, the command value received at time T is held, and the storage device 4 ends the voltage control of the DC power line 6 and is used as the command value from the power supply equipment control unit 7 when the storage device 4 ends the voltage control of the DC power line 6 and resumes the charge and discharge power control.

In Figure 6, the discharge power of the storage device 4 immediately before time T is -55 kW. When the storage device 4 receives a charge/discharge power command to discharge -40 kW from the power supply equipment control unit 7 at time T, since the command value of -40 kW is larger than the actual value of -55 kW, the storage device 4 ends the voltage control of the DC power line 6 and performs discharge power control according to the command value of -40 kW. At this time, the voltage VD of the DC power line 6 is controlled to the first voltage VD1 by the voltage control of the AC/DC inverter.

Figure 7 shows another example of the configuration of the power supply facility according to the first embodiment of the present invention. In Figure 7, an electric vehicle connection unit 611 is installed on the DC power line 6. The electric vehicle 11 is connected to the DC power line 6 via the electric vehicle connection unit 611. The electric vehicle connection unit 611 is a cable connector branched from the DC power line 6, and is an electrical contact between the electric vehicle 11 and the DC power line 6. The electric vehicle 11 is, for example, an electric car, an electric agricultural machine, a drone, etc., and is not necessarily always provided in the power supply facility 1. The electric vehicle 11 has a storage battery 41 and a DC/DC converter 42, and can charge the storage battery 41 by controlling the charging power by itself using a DC power supply. In addition, the power stored in the storage battery 41 can be discharged by DC discharge under the control of the DC/DC converter 42.

The power supply equipment 7 can issue charge/discharge power commands or charge/discharge current commands, upper and lower charge/discharge current limits, and upper and lower SOC limits to the electric vehicle 11, and can operate in the same manner as the example configuration shown in FIG. 1 and the examples of power and DC power line voltage of the power supply equipment shown in FIGS. 2 to 6.

In FIG. 7, the electric vehicle 11 may be configured not to have a DC/DC converter 42, in which case it may be connected via a separate external DC/DC converter 42.

Figure 8 shows another example of the configuration of the power supply facility according to the first embodiment of the present invention, which is a connection example in the case where the electric vehicle 11 does not have a DC/DC converter 42. In Figure 8, one end of the DC/DC converter 42 is connected to the DC power line 6, and an electric vehicle connection unit 611 is installed at the other end of the DC/DC converter 42. The electric vehicle 12 is connected to the DC power line 6 via the DC/DC converter 42 and the electric vehicle connection unit 611. The electric vehicle connection unit 611 is a cable connector for supplying the output of the DC/DC converter 42 to the electric vehicle 12. The electric vehicle 12 is, for example, an electric automobile, an electric agricultural machine, a drone, etc., and is not necessarily always provided in the power supply facility 1. The electric vehicle 12 has a storage battery 41, and the storage battery 41 is charged and discharged by the charge/discharge power control of the DC/DC converter 42. The configuration shown in Figure 8 can also perform the same operation as the configuration shown in Figure 7.

Figure 9 shows an example of the configuration of a power supply facility according to Example 2 of the present invention. In this example, the power supply facility 1 includes a received power measurement unit 12 in addition to the configuration shown in Example 1. The following describes the differences from Example 1.

This embodiment is applied to a power supply facility 1 and a load 10 that are connected to an AC power source 9 on the condition that reverse power flow is not allowed. In a connection that does not allow reverse power flow, a reverse power flow relay is installed at the receiving point, and the circuit breaker opens when reverse power flow occurs. When power is supplied to the load 10 using the power generated by the solar cell 2 and the discharged power of the power storage device 4, the occurrence of reverse power flow must be prevented so that the circuit breaker does not open.

The power supply equipment 7 issues a command for the upper limit of the converted power to the AC/DC inverter 5 and a command for charging/discharging power or a command for charging/discharging current to the battery 4 at regular intervals (e.g., one minute), so if the power consumption of the load 10, which takes a time longer than the regular interval, decreases gradually, reverse power flow can be prevented. However, if the power consumption of the load 10 decreases suddenly in a time shorter than the regular interval, the command value update of the power supply equipment 7 cannot be kept up, reverse power flow occurs, and the circuit breaker is opened. If the command period of the power supply equipment 7 is set to a short time (e.g., 0.1 seconds) to prevent reverse power flow, the equipment cost of the power supply equipment 7 will increase.

In this embodiment, the receiving power measurement unit 12 measures the power at the receiving point 91 of the AC power source 9, and transmits an AC output stop command 13 to the AC/DC inverter 5 while the receiving power is below a predetermined value (e.g., 1 kW). When the AC/DC inverter 5 receives the AC output stop command 13, it sets the upper limit of the conversion power to 0 kW from the time of reception until it receives a new conversion power upper limit command from the power supply equipment 7. After the time when it receives a new conversion power upper limit command from the power supply equipment 7, the upper limit of the conversion power of the AC/DC inverter 5 is set to the minimum of the rated power of the AC/DC inverter 5 and the conversion power upper limit commanded by the power supply equipment control unit 7.

Figure 10 shows an example of control of the power of each component and the voltage VD of the DC power line when the second embodiment of the present invention is applied. In this embodiment, as in the first embodiment, the converted power P5 of the AC/DC inverter 5 is positive when output to the AC side and negative when input (received power) from the AC side. Also, the charging/discharging power P4 of the storage device 4 is positive when discharging and negative when charging. The output P3 of the first DC/DC converter 3 is positive.

The time when the power storage device 4 and the AC/DC inverter 5 receive a command from the power supply equipment control unit 7 is set to 0. The power supply equipment control unit 7 transmits commands at a constant cycle T. Therefore, the next time when the power storage device 4 and the AC/DC inverter 5 receive a command is at time T.

At time 0, the power supply equipment control unit 7 commands the upper limit of the conversion power P5 of the AC/DC inverter 5 to be set to 50 kW. The storage device 4 has a charge/discharge power upper limit of 30 kW and a charge/discharge power lower limit of -30 kW, and is discharging at 30 kW to supply power to the load 10. For simplicity's sake, the output of the first DC/DC converter 3 at time 0 is set to a constant 10 kW. At this time, the sum of the output P3 of the first DC/DC converter 3 and the discharge power P4 of the storage device 4 is 40 kW, which is less than the upper limit of the conversion power P5 of the AC/DC inverter 5. Therefore, the AC/DC inverter 5 can control the voltage VD of the DC power line 6 to the first voltage VD1 by converting power by 40 kW.

When the AC/DC inverter 5 receives the AC output stop command 13 at time T1, the upper limit of the conversion power P5 of the AC/DC inverter 5 is updated to 0 kW. Therefore, the conversion power of the AC/DC inverter 5 was 40 kW until time T1, but becomes 0 kW after time T1. Then, the voltage VD of the DC power line 6 rises, and at time T2, the voltage VD of the DC power line 6 exceeds the second voltage VD2.

When the voltage VD of the DC power line 6 is equal to or higher than the second voltage VD2, the storage device 4 stops the charge/discharge power control instructed by the power supply equipment control unit 7 and executes voltage control of the DC power line 6. In this embodiment, the storage device 4 executes voltage control with the second voltage VD2 as a target value. The storage device 4 also executes voltage control with a discharge power equal to or higher than the charge/discharge power lower limit instructed by the power supply equipment control unit 7 or a discharge current equal to or higher than the charge/discharge current lower limit instructed by the power supply equipment control unit 7. In this embodiment, it is assumed that -30 kW is instructed as the charge/discharge power lower limit.

At time T, the upper limit of the conversion power P5 of the AC/DC inverter 5 is updated to the minimum of the rated power of the AC/DC inverter 5 and the upper limit of the conversion power received from the power supply equipment control unit 7. In this embodiment, it is updated to 30 kW.

The power storage device 4 updates the upper and lower limit values of the charge/discharge power or the upper and lower limit values of the charge/discharge current, and the upper and lower limit values of the SOC to the new upper and lower limit values received from the power supply equipment control unit 7.

At time T, the voltage VD of the DC power line 6 is equal to or greater than the second voltage VD2 and less than the third voltage VD3, so the storage device 4 compares the charge/discharge power command or charge/discharge current command (called a command value in this embodiment) received from the power supply equipment control unit 7 at time T with the actual charge/discharge power or charge/discharge current (called an actual value in this embodiment) at time T, with the power and current in the discharging direction being positive.

If the command value is smaller than the actual value, the storage device 4 ends the voltage control of the DC power line 6 and performs charge/discharge power control according to the command value. If the command value is larger than the actual value, the voltage control of the DC power line 6 continues. In this embodiment, it is assumed that a command value of 10 kW, which is larger than the actual value, is received. At this time, the storage device 4 continues the voltage control of the DC power line 6.

After time T, the AC/DC inverter 5 starts controlling the voltage VD of the DC power line 6 to the first voltage VD1 with the upper limit of the converted power of 30 kW. Meanwhile, the storage device 4 increases the discharge power in accordance with the increase in the converted power of the AC/DC inverter 5 in order to continue the voltage control of the DC power line 6. At time T3, when the charge/discharge power of the storage device 4 reaches the charge/discharge power of 10 kW commanded by the power supply equipment control unit 7 at time T, the storage device 4 ends the voltage control of the DC power line 6 and performs charge/discharge power control at 10 kW commanded by the power supply equipment control unit 7. Then, the voltage VD of the DC power line 6 is controlled to the first voltage VD1 by the voltage control of the AC/DC inverter.

In this embodiment, the power storage device 4 can be replaced with the configuration of the electric vehicle connection part 611 and the electric vehicle 11 shown in FIG. 7 of the first embodiment.

Figure 11 shows an example of the configuration of a power supply facility according to Example 3 of the present invention. In this example, in addition to the power storage device 4, a power storage device 4A is connected to the DC power line 6. Like the power storage device 4, the power storage device 4A is composed of a storage battery 41A and a DC/DC converter 42A, and the storage battery 4A can be charged and discharged by controlling the DC/DC converter 42A. The following describes the differences from Examples 1 and 2.

In this embodiment, when the voltage VD of the DC power line 6 becomes equal to or greater than the second voltage VD2 or less than the fourth voltage VD4, if the storage device 4 and the storage device 4A each independently control the voltage of the DC power line 6, their voltage controls may interfere with each other, causing the voltage VD of the DC power line 6 to become unstable. Therefore, when two or more storage devices are connected to the DC power line 6, the storage devices control the voltage of the DC power line 6 in one of the following two ways.

The first is droop control. The power supply equipment control unit 7 transmits a charge/discharge power command or a charge/discharge current command, a charge/discharge power upper/lower limit command or a charge/discharge current upper/lower limit command, and an SOC upper/lower limit command to the storage device 4 and the storage device 4A. A droop gain is set in advance for the storage device 4 and the storage device 4A. Then, when the voltage VD of the DC power line 6 is equal to or higher than the second voltage VD2 or equal to or lower than the fourth voltage VD4, the storage device 4 and the storage device 4A control the voltage VD of the DC power line 6 to the second voltage VD2 or the fourth voltage VD4 using the droop gain.

The droop gain may be transmitted sequentially from the power supply equipment control unit 7. That is, the power supply equipment control unit 7 transmits a charge/discharge power command or a charge/discharge current command, a charge/discharge power upper and lower limit command or a charge/discharge current upper and lower limit command, an SOC upper and lower limit command, and a droop gain to the storage device 4 and the storage device 4A. Then, when the voltage VD of the DC power line 6 is equal to or higher than the second voltage VD2 or equal to or lower than the fourth voltage VD4, the storage device 4 and the storage device 4A perform droop control according to the droop gain received from the power supply equipment control unit 7, and control the voltage VD of the DC power line 6 to the second voltage VD2 or the fourth voltage VD4.

However, when the charge/discharge power or charge/discharge current determined according to the droop gain is outside the range of the upper and lower charge/discharge power limit values or the upper and lower charge/discharge current limit values commanded by the power supply equipment control unit 7, the storage device 4 and the storage device 4A perform charging and discharging at the commanded upper and lower charge/discharge power limit values or the commanded upper and lower charge/discharge current limit values. Also, when the SOC of the storage battery 41 and the storage battery 41A reaches the commanded SOC upper limit value, the lower limit value of the discharge power is set to 0 kW and charging is not performed, and when the commanded SOC lower limit value is reached, the upper limit value of the discharge power is set to 0 kW and discharging is not performed.

The second method is to set a voltage control switching priority for the power storage device. In this method, the power storage device stops the charge/discharge power control commanded by the power supply equipment control unit 7, and the second voltage DV2 and fourth voltage DV4, which are thresholds for executing the voltage control of the DC power line 6, are set for each power storage device connected to the DC power line 6.

In this embodiment, the storage device 4 stops the charge/discharge power control instructed by the power supply equipment control unit 7 at the second voltage VD2 and the fourth voltage VD4, and executes voltage control of the DC power line 6. Also, the storage device 4A stops the charge/discharge power control instructed by the power supply equipment control unit 7 at the second voltage VD2A and the fourth voltage VD4A, and executes voltage control of the DC power line 6.

The magnitude relationship between the second voltage VD2 and the second voltage VD2A and the magnitude relationship between the fourth voltage VD4 and the fourth voltage VD4A are determined independently, and the voltage control switching priority is reflected in this magnitude relationship. Here, the maximum value of the second voltage VD2 and the second voltage VD2A is set to be less than the third voltage, and the minimum value of the second voltage VD2 and the second voltage VD2A is set to be higher than the first voltage. In addition, the maximum value of the fourth voltage VD4 and the fourth voltage VD4A is set to be less than the first voltage, and the minimum value of the fourth voltage VD4 and the fourth voltage VD4A is set to be higher than the minimum DC voltage.

The second voltage VD2, the second voltage VD2A, the fourth voltage VD4, and the fourth voltage VD4A are determined by a command from the power supply equipment control unit 7, an input from a source other than the power supply equipment control unit 7 possessed by the storage device 4 and the storage device 4A, or the storage device 4 and the storage device 4A themselves. In this embodiment, they are determined by a command from the power supply equipment control unit 7, and are as follows: first voltage VD1 < second voltage VD2 < second voltage VD2A < third voltage VD3, first voltage VD1 > fourth voltage VD4 > fourth voltage VD4A > minimum DC voltage.

Figure 12 shows an example of control of the power of each component and the voltage VD of the DC power line when the third embodiment of the present invention is applied. In this figure, the time when the power storage devices 4, 4A, and AC/DC inverter 5 receive commands from the power supply equipment control unit 7 is set to 0. The power supply equipment control unit 7 transmits commands at a constant cycle T. Therefore, the next time the power storage devices 4, 4A, and AC/DC inverter 5 receive a command is at time T.

At time 0, the power supply equipment control unit 7 commands the AC/DC inverter 5 to set the upper limit of the conversion power P5 to 50 kW. The storage device 4 and the storage device 4A are set with a charge/discharge power upper limit of 10 kW and a charge/discharge power lower limit of -20 kW, and are discharging at 10 kW to supply power to the load 10. Also, at time 0, the output of the first DC/DC converter 3 is 20 kW. At this time, the sum of the output of the first DC/DC converter 3 and the discharge power of the storage device 4 and the storage device 4A is 40 kW, which is less than the upper limit of the conversion power P5 of the AC/DC inverter 5. Therefore, the AC/DC inverter 5 can control the voltage VD of the DC power line 6 to the first voltage VD1 by converting power by 40 kW.

When the output power P3 of the first DC/DC converter 3 increases due to fluctuations in solar radiation from time 0 to time T1, the AC/DC inverter 5 increases the converted power P5 to control the voltage VD of the DC power line 6 to the first voltage VD1. At time T1, the output power P3 of the first DC/DC converter 3 becomes 30 kW, and the converted power P5 of the AC/DC inverter 5 reaches the upper limit of 50 kW.

After time T1, if the output power of the first DC/DC converter 3 increases further, the AC/DC inverter 5 cannot increase the conversion power P5 from 50 kW, and the voltage VD of the DC power line 6 rises from the first voltage VD1. Then, at time T2, it reaches a second voltage VD2 (e.g., 365 V) that is higher than the first voltage VD1.

When the voltage VD of the DC power line 6 is equal to or higher than the second voltage VD2, the storage device 4 stops the charge/discharge power control instructed by the power supply equipment control unit 7 and executes voltage control of the DC power line 6. In this embodiment, the storage device 4 executes voltage control with the second voltage VD2 as a target value. The storage device 4 also executes voltage control with a discharge power equal to or higher than the charge/discharge power lower limit instructed by the power supply equipment control unit 7 or a discharge current equal to or higher than the charge/discharge current lower limit instructed by the power supply equipment control unit 7. In this embodiment, -20 kW is instructed as the charge/discharge power lower limit.

At this time, the power storage device 4A continues the charge/discharge power control commanded by the power supply equipment control unit 7. After time T2, the power storage device 4 executes voltage control with the second voltage VD2 as the target value due to the decrease in discharge power.

At time T3, the discharge power of the storage device 4 reaches -20 kW. After time T3, even if the output power P3 of the first DC/DC converter 3 increases further, the storage device 4 cannot increase the charging power, so the voltage VD of the DC power line 6 rises further from the second voltage VD2, and at time T4, it reaches the second voltage VD2A (e.g., 375 V), which is higher than the second voltage VD2.

When the voltage VD of the DC power line 6 is equal to or higher than the second voltage VD2A, the storage device 4A stops the charge/discharge power control instructed by the power supply equipment control unit 7 and executes voltage control of the DC power line 6. In this embodiment, the storage device 4A executes voltage control with the second voltage VD2A as the target value. The storage device 4A also executes voltage control with a discharge power equal to or higher than the charge/discharge power lower limit instructed by the power supply equipment control unit 7 or a discharge current equal to or higher than the charge/discharge current lower limit instructed by the power supply equipment control unit 7. In this embodiment, -20 kW is instructed as the charge/discharge power lower limit.

After time T4, the storage device 4A executes voltage control with the second voltage VD2A as a target value due to a decrease in discharge power. At this time, when the solar radiation decreases and the power generated by the solar cell 2 decreases, at time T5, the voltage VD of the DC power line 6 becomes less than the second voltage VD2A. At this time, the storage device 4A ends the voltage control of the DC power line 6 and resumes the charge/discharge power control commanded by the power supply equipment control unit 7. The voltage VD of the DC power line 6 is then controlled to the second voltage VD2 by the voltage control of the storage device 4.

Similarly, after time T5, when the solar radiation decreases and the power generated by the solar cell 2 decreases, at time T6, the voltage VD of the DC power line 6 becomes less than the second voltage VD2. At this time, the storage device 4 ends the voltage control of the DC power line 6 and resumes the charge/discharge power control commanded by the power supply equipment control unit 7. Then, the voltage VD of the DC power line 6 is controlled to the first voltage VD1 by the voltage control of the AC/DC inverter 5.

At time T when a new command is received from the power supply equipment control unit 7, the voltage VD of the DC power line 6 is the first voltage VD1. At this time, the upper limit of the conversion power P5 of the AC/DC inverter 5 is updated to the minimum of the rated power P5 of the AC/DC inverter 5 and the conversion power upper limit value received from the power supply equipment control unit 7 at time T. In addition, the lower limit of the conversion power P5 of the AC/DC inverter 5 becomes the maximum of the rated power of the AC/DC inverter 5 × (-1) and the conversion power lower limit value commanded from the power supply equipment control unit 7. The storage device 4 operates according to the charge/discharge power command or charge/discharge current command received from the power supply equipment control unit 7 at time T. In addition, the charge/discharge power upper and lower limit values or the charge/discharge current upper and lower limit values, and the SOC upper and lower limit values are updated.

As described above, when setting voltage control switching priorities for the storage devices in a configuration in which multiple storage devices are connected to the DC power line 6, the voltage VD of the DC power line 6 can be controlled by setting the second voltage in Examples 1 and 2 to the second voltage VD2, the second voltage VD2A, ... for each storage device.

In addition, in a configuration in which three or more storage devices are connected, it is also possible to set voltage control switching priorities for the group of storage devices that perform droop control and for each storage device that does not perform droop control.

For example, when the power storage device 4, the power storage device 4A, the power storage device 4B, and the power storage device 4C are connected to the DC power line 6, the power storage device 4 and the power storage device 4A can be set to execute droop control, and the power storage device 4B and the power storage device 4C can be set not to execute droop control. At this time, the voltages at which the power storage device 4 and the power storage device 4A start droop control are set to the second voltage VD2 and the fourth voltage VD4, and the voltages at which the power storage device 4B and the power storage device 4C start voltage control of the DC power line 6 are set to the second voltage VD2B and the fourth voltage VD4B, and the second voltage VD2C and the fourth voltage VD4C, respectively.

The magnitude relationship between the second voltage VD2, the second voltage VD2B, and the second voltage VD2C and the magnitude relationship between the fourth voltage VD4, the fourth voltage VD4B, and the fourth voltage VD4C can be set independently and arbitrarily. However, the maximum values of the second voltage VD2, the second voltage VD2B, and the second voltage VD2C are set to be less than the third voltage VD3, and the minimum values are set to be higher than the first voltage VD1. Also, the maximum values of the fourth voltage VD4, the fourth voltage VD4B, and the fourth voltage VD4C are set to be less than the first voltage VD1, and the minimum values of the fourth voltage VD4, the fourth voltage VD4B, and the fourth voltage VD4C are set to be higher than the minimum DC voltage.

In this embodiment, the power storage device 4 and the power storage device 4A can be replaced with the configurations of the electric vehicle connection part 611 and the electric vehicle 11 shown in FIG. 7 of the first embodiment, respectively.

Figure 13 shows an example of the configuration of a power supply facility according to Example 4 of the present invention. In this example, one end (primary side) of a second DC/DC converter 60 is connected to a first DC power line 61 to which a first DC/DC converter 3 and an AC/DC inverter 5 are connected. A second DC power line 62 is connected to the other end (secondary side) of the second DC/DC converter 60.

That is, the second DC/DC converter 60 splits the DC power line 6 in the example configuration of the power supply facility in Example 1. The second DC/DC converter 60 is a bidirectional converter, and can charge the power generated by the solar cell 2 or the power of the AC power source 9 received via the AC/DC inverter 5 to the power storage device 4, and can supply the power of the power storage device 4 to the load 10 via the AC/DC inverter 5.

Depending on the configuration of the solar cell 2, the output voltage of the first DC/DC converter 3 may be high (e.g., 1000V). In the configurations described in Examples 1 to 3, the first voltage, which is the voltage control target value of the AC/DC inverter 5, is set to a high voltage (e.g., 1000V), and as a result, the withstand voltage of the storage device 4 needs to be increased. However, by installing the second DC/DC converter 60 and stepping down the output voltage (primary side voltage) of the first DC/DC converter 3, it is possible to prevent the withstand voltage of the storage device 4 from becoming too high.

In addition, by making the second DC/DC converter 60 an insulated bidirectional converter, it is possible to insulate the first DC/DC converter 3 from the power storage device 4. As a result, even if the second DC power line 62 deteriorates and the conductor portion is exposed and a human body touches the exposed portion, a current path is not formed from the solar cell 2, which is the power source, to the human body, so electric shock can be prevented even if the first DC/DC converter 3 is a non-insulated type (e.g., a boost chopper circuit).

In this embodiment, the second DC/DC converter 60 always controls the ratio of the primary voltage to the secondary voltage V2 to a constant value N during operation. That is, (primary voltage) = N x (secondary voltage). Here, N = 20/7. The rated power of the second DC/DC converter 60 is equal to the rated power of the DC/DC converter 42 of the storage device 4.

By constant voltage ratio control by the second DC/DC converter 60 described above, when the voltage of the second DC power line 62 is the first voltage VD1 (350V), the second voltage VD2 (370V), the third voltage VD3 (390V), or the fourth voltage VD4 (340V) shown in Example 1, the primary voltage of the second DC/DC converter 60, i.e., the voltage of the first DC power line 61, is the first voltage VD1' (1000V), the second voltage VD2' (1057V), the third voltage VD3' (1114V), or the fourth voltage VD4' (971V), respectively.

In this embodiment, the power storage device 4 operates in the same manner as in the first embodiment. That is, when the voltage value of the second DC power line 62 is equal to or greater than a second voltage that is higher than the first voltage, and when the voltage value is less than a fourth voltage that is lower than the first voltage, the power storage device 4 performs voltage control of the second DC power line 62.

The voltage control target value of the AC/DC inverter 5 is set to the first voltage VD1', and the threshold voltage at which the first DC/DC converter 3 ends MPPT control and performs voltage control is set to the third voltage VD3'. When the AC/DC inverter 5 can control the voltage of the first DC power line 61 to the first voltage VD1', the voltage of the second DC power line 62 becomes the first voltage VD1.

As described in the first embodiment, the AC/DC inverter 5 may not be able to control the voltage of the first DC power line 61 to the first voltage VD1' due to the upper and lower limits of the converted power, and the voltage may rise from the first voltage VD1' to the second voltage VD2' (1057 V) or fall to the fourth voltage VD4' (971 V). At this time, the voltage of the second DC power line 62 also rises or falls in response to the rise or fall of the voltage of the first DC power line 61. If the voltage of the first DC power line 61 rises to the second voltage VD2', the voltage of the second DC power line 62 rises to the second voltage VD2, and the storage device 4 starts controlling the voltage of the second DC power line 62. Even if the storage device 4 executes voltage control, if the voltage of the second DC power line 62 rises and reaches the third voltage VD3, the voltage of the first DC power line 61 rises to the third voltage VD3'. At this time, the first DC/DC converter 3 ends the MPPT control and controls the voltage of the first DC power line 61.

As described above, the voltage control target value of the AC/DC inverter 5 is set to the first voltage VD1', the threshold voltage at which the first DC/DC converter 3 ends MPPT control and performs voltage control is set to the third voltage VD3', and other controls and operations are similar to those of the first embodiment, so that the configuration example of the power supply equipment in this embodiment can achieve the same effects as those of the first embodiment. The same is true for the second and third embodiments.

Figure 14 shows an example of the configuration of a power supply facility in the fifth embodiment of the present invention. In this embodiment, the first DC/DC converter 3, the AC/DC inverter 5, and the storage device 4 are connected to the first DC power line 61, which is the primary side of the second DC/DC converter 60, and the storage device 4A is connected to the second DC power line 62, which is the secondary side of the second DC/DC converter 60. In other words, the storage devices are connected to both the primary side and the secondary side of the second DC/DC converter 60. The rated power of the second DC/DC converter 60 is equal to the rated power of the DC/DC converter 422 of the storage device 4A.

The second DC/DC converter 60 performs constant voltage ratio control (N=20/7) in the same manner as in Example 4. That is, when the voltage of the second DC power line 62 is the first voltage VD1 (350V), the second voltage VD2 (370V), the third voltage VD3 (390V), the fourth voltage VD4 (340V), the second voltage VD2 (365V), or the second voltage VD2A (375V) shown in Example 3, the voltage of the first DC power line 61 is the first voltage VD1' (1000V), the second voltage VD2' (1057V), the third voltage VD3' (1114V), the fourth voltage VD4' (971V), the second voltage VD2' (1043V), or the second voltage VD2A' (1071V), respectively.

The voltage control target value of the AC/DC inverter 5 is set to the first voltage VD1', and the threshold voltage at which the first DC/DC converter 3 ends MPPT control and performs voltage control is set to the third voltage VD3'. The threshold voltage at which the storage device 4 stops the charge/discharge power control instructed by the power supply equipment control unit 7 and performs voltage control of the first DC power line 61 is set to the second voltage VD2' or the second voltage VD2', and the fourth voltage VD4'. The other controls and operations are in accordance with the third embodiment, so that the configuration example of the power supply equipment in this embodiment can achieve the same effects as the third embodiment.

In this embodiment, the power storage device 4 and the power storage device 4A can be replaced with the configurations of the electric vehicle connection part 611 and the electric vehicle 11 shown in FIG. 7 of the first embodiment, respectively.

1...Power supply equipment 2...Solar cells (renewable energy source)
Reference Signs List 3: First DC/DC converter 4, 4A: Power storage device 5: AC/DC inverter 6: DC power line 7: Power supply equipment control unit 8: Power distribution line 9: AC power source 10: Load 12: Power receiving system side unit 13: AC output stop command 60: Second DC/DC converter 61: First DC power line 62: Second DC power line

Claims (8)

A power supply facility including a first conversion device arranged between an AC power line and a DC power line and performing power conversion, a second conversion device arranged between the DC power line and a storage battery and performing power conversion, and a third conversion device arranged between the DC power line and a renewable energy power source and performing power conversion,
a first conversion device controls a voltage of the DC power line to a first voltage, and a second conversion device controls a voltage of the DC power line to a second voltage when the first conversion device cannot control the voltage of the DC power line to the first voltage and the voltage of the DC power line exceeds a second voltage that is set higher than the first voltage;
the first conversion device and the third conversion device are connected to one end of a fourth conversion device by a first DC power line, and the other end of the fourth conversion device is connected to the second conversion device via the first DC power line;
the fourth conversion device controls a ratio of a voltage of the first DC power line to a voltage of the second DC power line to a constant value;
the first conversion device controls a voltage of the first DC power line to a voltage value obtained by multiplying the first voltage by the constant value;
the second conversion device controls the voltage of the second DC power line to the second voltage when the first conversion device is unable to control the voltage of the first DC power line to a voltage value obtained by multiplying the first voltage by the constant value and the voltage of the second DC power line exceeds the second voltage. The power supply facility according to claim 1 ,
the third conversion device controls the voltage of the DC power line to the third voltage when the voltage of the first DC power line exceeds a voltage value obtained by multiplying a third voltage by the constant value. The power supply facility according to claim 2 ,
The third conversion device controls the generated power output by the renewable energy power source using maximum power point tracking (MPPT) when the voltage of the first DC power line is equal to or lower than a voltage value obtained by multiplying the third voltage by the constant value. The power supply facility according to claim 1 ,
the fourth conversion device performs voltage control of the second DC power line when the voltage of the second DC power line falls below a fourth voltage that is lower than the first voltage. The power supply facility according to any one of claims 1 to 4 ,
a power storage device including a storage battery and a second conversion device that converts an output of the storage battery into power is connected to the first DC power line and the second DC power line;
a power storage device connected to the first DC power line, when a voltage of the first DC power line exceeds a voltage value obtained by multiplying the second voltage by the constant value, performing voltage control of the first DC power line. The power supply facility according to claim 5 ,
the power storage device connected to the first DC power line performs voltage control of the first DC power line when the voltage of the first DC power line falls below a voltage value obtained by multiplying a fourth voltage lower than the first voltage by the constant value. The power supply facility according to any one of claims 1 to 6 ,
The power supply facility is characterized in that the storage battery is mounted on an electric vehicle. The power supply facility according to any one of claims 1 to 7 ,
a power supply facility comprising a plurality of power storage devices each including a storage battery and a second conversion device that converts the output of the storage battery into power, the power storage devices each being connected to the DC power line, and a threshold value for executing voltage control of the DC power line and for each of the power storage devices being set to stop a commanded charge/discharge power control.

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