JP5452422B2 - Inverter - Google Patents

Description

  The present invention converts DC power from various power generation devices, various power storage devices, and other distributed power sources capable of outputting DC power into AC power, and connects the converted AC power to a commercial power source. In particular, output control is performed so that the power that is not allowed to flow backward to the commercial power source among the DC power related to the various distributed power sources does not flow backward to the commercial power source. It is about.

  Among the various distributed power sources described above, for example, in a distributed power source system in which a solar cell using sunlight is used as a distributed power source and DC power of the solar cell is converted into AC power and supplied to a load, a power conditioner is generally used. When the DC power of the solar cell is converted to AC power and the converted AC power is supplied to each household electrical appliance (home load), if the supplied power is less than the power consumption of the home load, If the power output from the power conditioner exceeds the power consumption of the household load, while the shortage power from the commercial power source flows forward from the power company, the surplus power flows backward to the commercial power source and the power company It is also possible to sell electric power (Patent Document 1).

  In such a case, the solar cell generates power on a sunny day, but cannot generate power on night or rainy days. In order to further reduce the electricity bill by reducing the amount of electricity used, a distributed power supply system in which, in addition to the solar battery, the power usage is less expensive than the power usage of a commercial power supply, for example, a system using a fuel cell as an example is used. Possible (Patent Document 2).

  However, in a distributed power system that uses a solar cell and a fuel cell in combination, the converted AC power from the fuel cell cannot flow backward to the commercial power source. The distributed power source that cannot flow backward to the commercial power source is not limited to the fuel cell. That is, fuel cells and the like are power generators that generate DC power themselves, including wind power generators, etc., but not only distributed power sources such as such power generators, but also power that can store DC power such as capacitors and storage batteries. Even when the storage device is used as a distributed power supply in a distributed power supply system, there is a case where a reverse power flow cannot be made to the commercial power supply side.

JP 2005-102432 A JP 2006-296097 A

  In the present invention, when DC power from a distributed power source that outputs DC power is DC / DC converted, DC / AC converted, and output as a converted AC output, the AC power cannot be reversed. It is an issue to be solved to enable control so as not to flow backward to the commercial power supply side.

  The power conditioner according to the present invention outputs DC power output from a distributed power source after DC / DC conversion and then DC / AC conversion, and the home load power consumption is PL and reverse power flow is impossible. The output relating to the distributed power supply is set as Pout2, and control is performed to maintain the relational expression of output Pout2 ≦ internal load power consumption PL so that the output Pout2 is not reversely flowed to the commercial power supply. .

  Preferably, the distributed power source is a device having a power generation function capable of generating direct current power including a battery and outputting the generated direct current power.

  Preferably, the distributed power source is a device that has a function of storing DC power including a capacitor, a storage battery, and the like and that can output the stored DC power.

  As described above, the distributed power source stores not only a battery or other power generation device that directly generates direct current power, including a fuel cell or a wind power generation device, but also stores direct current power such as a capacitor or a storage battery. Any power storage device capable of outputting the power and any other device capable of outputting the power can be included.

  Preferably, in a power conditioner having a solar battery and a storage battery, the DC / DC converter for DC / DC conversion of DC power output from the solar battery is an insulation type that uses an insulating transformer inside, and is output from the storage battery. The DC / DC converter that converts the DC power to DC / DC can be a non-insulating type that does not use an insulating transformer.

  Preferably, in a power conditioner having a solar cell, a fuel cell, and a storage battery, the DC / DC converter for DC / DC converting DC power output from the solar cell and the fuel cell is an insulation type, and is output from the storage battery. The DC / DC converter that performs DC / DC conversion of the direct current power can be a non-insulated type.

  ADVANTAGE OF THE INVENTION According to this invention, in the distributed power supply system, when the output of a distributed power supply is made non-reversible, it can control so that the electric power regarding the output of the distributed power supply is not reversely flowed to the commercial power supply side. .

FIG. 1 is a diagram showing a distributed power supply system according to an embodiment of the present invention. 2A is a diagram showing an internal block of a DC / DC converter that DC / DC converts the solar cell output of FIG. 1, and FIG. 2B is a DC / DC that DC / DC converts the fuel cell output of FIG. It is a figure which shows the internal block of a converter. FIG. 3 is a diagram showing an internal block of the control device provided in the system of FIG. FIG. 4 is a diagram showing a distributed power supply system according to another embodiment of the present invention.

  Hereinafter, a power conditioner according to an embodiment of the present invention and a distributed power supply system using the same will be described with reference to the accompanying drawings. FIG. 1 shows a configuration of a distributed power supply system according to the embodiment. In FIG. 1, reference numeral 1 denotes a solar cell (solar cell power generation element or device) which is an example of a power generation element capable of reverse flow, and 2 denotes a fuel cell (fuel cell power generation element or device) which is an example of a power generation element where reverse power flow is not possible. 3 is a power conditioner, 4 is a power distribution facility, 5 is a home load, 6 is a power sale meter, 7 is a power purchase meter, 8 is a commercial power supply, and 9 is a power meter.

  The solar cell 1 converts solar energy into electric energy and supplies DC power to the power conditioner 3.

  The fuel cell 2 is a power generation device that uses fuel. For example, hydrogen and oxygen are reacted to generate DC electrical energy, and DC power is supplied to the power conditioner 3.

  The power conditioner 3 converts the DC power from the solar cell 1 and the fuel cell 2 into AC power having a commercial frequency (50 Hz or 60 Hz) and supplies the AC power to the household load 5 and the commercial power source 8.

  The power distribution facility 4 is a facility for distributing power to general households.

  The household load 5 is a load of various electric devices connected to the power distribution facility 4.

  The household load 5 includes a reverse power flow prevention heater provided in the hot water storage tank and auxiliary power for operating the fuel cell so that the power generated by the fuel cell 2 does not flow backward.

  The power sale meter 6 is a meter that measures the amount of power when selling power to the commercial power supply 8 side.

  The electric power purchase meter 7 is a meter that measures the amount of electric power when electric power is purchased from the commercial power supply 8 side.

  The power meter 9 measures the power consumption of the household load 5.

In the above distributed power supply system, the power conditioner 3 converts the direct current power of the solar battery 1 and the fuel cell 2 that are the distributed power supply into alternating current power, and supplies the converted alternating current power to the home load 5. When the supplied power is lower than the power consumption of the household load 5, the shortage power flows forward from the commercial power supply 8 to purchase power from the power company, while the output power of the power conditioner 3 is When the power consumption is exceeded, the output power of the solar cell 1 capable of reverse flow with the surplus power is reversely flowed to the commercial power source 8 and sold to the power company. The amount of power purchased at that time is measured by the power purchase meter 7, and the amount of power sold is measured by the power sale meter 6.

  In such a distributed power supply system, the power conditioner 3 includes a measuring device 3a for measuring the voltage and current of the DC output of the solar cell 1 and power as required, and the voltage of the DC output of the fuel cell 2. , Measuring device 3b for measuring current and electric power as required, DC / DC converter 3c for DC / DC conversion of DC output of solar cell 1, and DC / DC for DC / DC conversion of DC output of fuel cell 2 DC / AC for DC / AC conversion of the outputs of the converter 3d, the DC output voltage measuring device 3e of the DC / DC converter 3c, the DC power measuring device 3f of the DC / DC converter 3d, and the DC / DC converters 3c and 3d. An inverter 3g, an AC output power measuring device 3p of the DC / AC inverter 3g, and a control device 3h for controlling these operations are included.

  As shown in FIGS. 2A and 2B, the DC / DC converters 3c and 3d step up or step down the switching circuits 3c1 and 3d1 that perform switching operation so as to convert the direct current input into alternating current, and the outputs of the switching circuits 3c1 and 3d1. And DC control circuits 3c3 and 3d3 for converting the secondary outputs of the transformers 3c2 and 3d2 into direct current, and control units 3c4 and 3d4 for controlling these DC / DC conversion operations. . The switching circuits 3c1 and 3d1 have, for example, a so-called one-stone inverter method, flyback method, center tap method, half bridge method, full bridge method, and the like depending on the configuration of a switching transistor such as a MOS transistor. The DC / DC converters 3c and 3d use the transformers 3c2 and 3d2. However, the present embodiment is not limited to the DC / DC converter using the transformer, and is a transformerless type DC / DC converter. Are also included in the present invention.

  For example, the DC / AC inverter 3g bridges four switching elements and converts the DC power from the DC / DC converters 3c and 3d into sinusoidal AC power synchronized with the commercial power supply 8 by PWM drive. Supply to commercial power supply 8. Of course, the present invention is not limited to this type of DC / AC inverter.

  Since the output voltage of the solar cell 1 and the fuel cell 2 is generally low, the DC / DC converters 3c and 3d boost the voltage to a voltage sufficient to form the AC voltage of the commercial power supply 8, and the boosted DC voltage is This is supplied to the DC / AC inverter 3g. In this case, when the output voltage of the solar cell 1 or the fuel cell 2 is high, the voltage is stepped down as necessary. In the DC / AC inverter 3g, the output portions of the DC / DC converters 3c and 3d are connected in parallel, and the output voltages of the DC / DC converters 3c and 3d are converted into commercial frequency alternating voltages, and an alternating current flows. .

  While the output voltage of the solar cell 1 varies depending on the amount of solar radiation and temperature, the output voltage of the fuel cell 2 decreases as the generated current increases. The outputs of the solar cell 1 and the fuel cell 2 are stepped up or stepped down by the DC / DC converters 3c and 3d of the power conditioner 3. The fuel cell 2 is generally capable of continuous rated operation as long as the fuel supply is not cut off, but the solar cell 1 is generally limited to daytime operation.

The control device 3h of the power conditioner 3 includes a microcomputer, and can perform control performed by the functional blocks shown in FIG. That is, the control device 3h roughly includes a memory 3h1 and a CPU 3h2. The memory 3h1 stores an operation control program for the control device 3h, and has a data processing work area, a data storage area, and the like. The CPU 3h2 performs the following control according to the program stored in the memory 3h1. That is, the CPU 3h2 in the control device 3h inputs the DC output voltage, current, and electric power as required, which are the measurement values of the measuring device 3a in the solar cell 1, and the solar cell 1 is calculated from these measurement values. The control command S1 is output-controlled to the DC / DC converter 3c so that the DC / DC converter 3c can operate at the maximum output point, and the direct current output voltage and current of the fuel cell 2 that is a measurement value of the measuring device 3a in the fuel cell 2 and as required. Then, based on these measured values and the output current command or output power command of the fuel cell 2, the control command S2 is output controlled to the DC / DC converter 3d. In the DC / DC converters 3c and 3d, the internal switching circuits 3c1 and 3d1 shown in FIGS. 2A and 2B are controlled by the PWM signals S3 and S4 in response to the control commands S1 and S2 from the CPU 3h2 of the control device 3h. To do. As a result, the power conditioner 3 including the DC / DC converters 3c and 3d is configured such that the output Pout2 of the fuel cell 2 measured by the power meter 3f is the power consumption PL of the home load 5 measured by the power meter 9. When smaller, the fuel cell 2 is operated within the allowable output range. If the measured value Pout3 of the power meter 3p that measures the output of the DC / AC inverter 3g determined from the output of the solar cell 1 and the output of the fuel cell 2 is larger than the power consumption PL of the household load 5, the surplus power The output power of the solar cell 1 capable of reverse power flow is sold, and if it is insufficient, it is purchased.

  The control command S2 receives the measured value PL of the power consumption at the household load 5 from the power meter 9, and the DC / DC is prevented from flowing backward from the measured value PL to the commercial power source 8. It is also a control command for controlling the operation of the DC converter 3d.

The DC / AC inverter 3g controls the AC output current of the DC / AC inverter 3g so that the DC voltage of the DC / AC inverter 3g measured by the voltage measuring device 3e becomes a desired value. By this control, the output power Pout3 of the DC / AC inverter 3g is controlled. The output power Pout3 is measured by the power meter 3p.

  That is, the CPU 3h2 of the control device 3h maintains the relational expression of Pout2 ≦ PL, with the AC power consumption (measured value of the power meter 9) PL in the home load 5 and the output of the DC / DC converter 3d as Pout2. The output power Pout2 of the DC / DC converter 3d is controlled. The data of the above relational expression in this case, the calculation program necessary for this control, and the like are stored in the memory 3h1. The CPU 3h2 refers to the data in the memory 3h1 and generates and outputs a control command according to the stored program. The CPU 3h2 inputs the measured value measured by the power measuring instrument 9 as the power consumption PL at the home load 5, and also inputs the measured value by the power measuring instrument 3f as the output power Pout2 of the fuel cell 2. A control command S2 is output to the control unit 3d4 of the DC / DC converter 3d so that the relational expression Pout2 ≦ PL is satisfied from PL, Pout2. In this case, the CPU 3h2 inputs the control command S2 to the DC / DC converter 3d so that the difference PL-Pout2 between the consumed AC power PL and the output of the DC / DC converter 3d is 0 or plus.

  The control unit 3d4 of the DC / DC converter 3d controls the switching operation of the circuit 3d1 by applying the PWM signal S4 to the switching circuit 3d1 in response to the control command S2. As a result, the AC output when the DC output Pout2 of the DC / DC converter 3d is converted into the AC output by the DC / AC inverter 3g is not supplied to the commercial power supply 8 as surplus power, but consumed by the household load 5. Used for. This prevents the power generated by the fuel cell 2 from flowing backward to the commercial power source 8. Here, the switching circuit 3d1 of the DC / DC converter 3d is configured, for example, by connecting a plurality of MOS transistors to a full bridge circuit, etc., and the PWM signal S4 is applied to the gate of each transistor from the control unit 3d4. Thus, the output Pout2 of the DC / DC converter 3d is controlled so as to satisfy the relational expression Pout2 ≦ PL.

  As described above, in the distributed power supply system of the embodiment, the distributed power source capable of reverse power flow is the solar cell 1 and the distributed power source not capable of reverse power flow is the fuel cell 2. The distributed power source is not limited to the solar cell 1, and the distributed power source that does not allow reverse power flow is not limited to the fuel cell 2.

  That is, in FIG. 4, 1a is a first distributed power source that can flow backward to the commercial power supply 8 side like a solar cell, and 2a cannot flow backward to the commercial power supply 8 side like a fuel cell. 2 shows a second distributed power source. The second distributed power source 2a is not limited to a battery other than a fuel cell, and also includes a power generation device such as a wind power generation device and does not generate power, but stores direct current power such as a capacitor or a storage battery and stores it. Any power storage device that can output power, and any other device that can output power are included.

  Although FIG. 4 shows the first distributed power source and the second distributed power source, it is apparent that a third distributed power source and a fourth distributed power source can be added as can be understood from the above description.

  Further, in FIG. 4, when a power conditioner having a solar cell as the first distributed power source 1a and a storage battery as the second distributed power source 2a is used, a DC / DC converter that DC / DC converts DC power output from the solar cell. Can be an insulation type that uses an insulation transformer inside, and a DC / DC converter that DC / DC converts DC power output from a storage battery can be a non-insulation type that does not use an insulation transformer inside.

  Similarly, in FIG. 4, when a power conditioner having a solar cell as the first distributed power source 1a and a fuel cell and a storage battery as the second distributed power source 2a, the DC output from the solar cell is DC / DC converted, respectively. Both the DC / DC converter and the DC / DC converter that converts DC power output from the fuel cell into DC / DC are of an insulating type that uses an insulating transformer inside, and DC / DC that converts DC power output from the storage battery into DC / DC. The DC converter can be a non-insulating type that does not use an insulating transformer. In the case of a storage battery, the DC / DC converter is a bidirectional type. Here, the reason why the DC / DC converters of the solar cell and the fuel cell are insulated is to suppress the leakage current flowing from them to the ground, and the DC / DC converter of the storage battery is made non-insulated. The reason is that the leakage current flowing to the ground is small. Note that the DC / DC converter of the solar cell can also be made non-insulating if it is constructed so that the leakage current from the solar cell is reduced.

  4, parts that are similar to or correspond to those in FIGS. 1 to 3 are given the same reference numerals.

  Also in the control device 3h shown in FIG. 4, the load power consumption is PL, the output of the second DC / DC converter 3d is Pout2, and the relational expression of Pout2 ≦ PL is set so that the output Pout2 is not reversely flowed to the commercial power supply 8. The control to maintain is performed.

In the above, the home load power consumption PL was measured using the power meter 9, but without using the power meter 9 , the output of the power meter 3p for measuring the AC output Pout3 of the DC / AC inverter 3g is sold. It can also be obtained by using the output of the electricity meter 6 and the output of the electricity purchase meter 7.

  As described above, in the power conditioner 3 according to the present embodiment, it is possible to control so that the generated power from the fuel cell 2 that is the reverse flow impossible power generation element does not flow backward to the commercial power supply 8 side.

1 Solar cell 1a First distributed power source 2 Fuel cell (distributed power source)
2a Second distributed power source 3 Power conditioners 3a, 3b, 3e, 3f, 3p Measuring instrument 3c, 3d DC / DC converter 3g DC / AC inverter 3h Control device 3h1 Memory 3h2 CPU
4 Power distribution equipment 5 Domestic load 6 Power meter 7 Power meter 8 Commercial power supply 9 Power meter

Claims (3)

A plurality of DC / DC converters that DC / DC convert DC power of each distributed power source corresponding to each of the plurality of distributed power sources, and output the converted DC power, and each of the plurality of DC / DC converters output unit are connected in parallel, the conversion DC power from the output portion of the DC / DC converter converts DC / AC, followed a DC / AC inverter and outputs the converted AC power, these operations to store the program A control device for controlling based on the control command,
The control device
The output of one DC / DC converter that performs DC / DC conversion of DC power related to a distributed power source that allows load power to be PL and reverse power flow to a commercial power source is Pout1, and that that relates to a distributed power source that is not capable of reverse power flow When the output of one DC / DC converter that converts DC power into DC / DC is Pout2, and the output of the DC / AC inverter to which Pout1 and Pout2 are input is Pout3,
When Pout3 is larger than PL, the power related to the output of Pout1 among the surplus power can be sold to a commercial power supply, and control is performed by a DC / AC inverter that can purchase power when Pout3 is smaller than PL. With
A power conditioner that performs control to maintain a relational expression of Pout2 ≦ PL so that power related to the output of Pout2 does not flow backward to a commercial power source.   When one of the plurality of distributed power sources is a solar battery and the other is a storage battery, the DC / DC converter for DC / DC conversion of DC power output from the solar battery is an insulation type, and is output from the storage battery. The power conditioner according to claim 1, wherein the DC / DC converter that performs DC / DC conversion of the direct current power is a non-insulated type.   When one of the plurality of distributed power sources is a solar cell, the other is a fuel cell, and the other is a storage battery, DC / DC that converts DC power output from each of the solar cell and the fuel cell is DC / DC converted. The power conditioner according to claim 1, wherein the DC converter is an insulating type, and the DC / DC converter that performs DC / DC conversion of the DC power output from the storage battery is a non-insulating type.

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