WO2007004514A1

WO2007004514A1 - Photovoltaic power generation system utilizing commercial system power supply

Info

Publication number: WO2007004514A1
Application number: PCT/JP2006/313006
Authority: WO
Inventors: Ayumi Yagi; Mitsuo Okamoto; Koji Miyamae
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2005-07-06
Filing date: 2006-06-29
Publication date: 2007-01-11
Also published as: JP2007018180A

Abstract

A photovoltaic power generation system (100) comprises a solar cell module (1A), a step up/down circuit (2A) for regulating the voltage level of DC power generated from the solar cell module (1A), a rectifier circuit (5) for converting the AC power from a commercial system power supply (6) into a DC power, and an inverter (3) for producing an AC power to be supplied to a load (7A) from the DC power having a voltage level regulated by the step up/down circuit (2A) and the DC power converted by the rectifier circuit (5).

Description

Specification

Solar power generation system using commercial power supply

Technical field

TECHNICAL FIELD [0001] The present invention relates to a solar power generation system, and more particularly to a solar power generation system using a commercial power supply.

Background art

[0002] In recent years, the use of clean and inexhaustible solar energy has attracted attention as a measure against the energy crisis caused by fossil fuel depletion and the prevention of global warming caused by carbon dioxide emissions. Along with this, solar cell modules that convert solar energy into electrical energy have rapidly spread and have already been introduced into ordinary households, not just large-scale private and public facilities.

[0003] FIG. 6 is a diagram showing a daily power generation amount of a general solar cell. Referring to Fig. 6, sufficient power generation can be obtained during clear daytime, whereas power generation decreases sharply at sunrise and sunset, and no power generation can be obtained at night. In cloudy weather and rainy weather, the amount of power generation is greatly reduced compared to that in fine weather.

[0004] In order to cope with such fluctuations in the amount of power generated by solar cells, the following solar power generation systems have been proposed.

FIG. 7 is a diagram showing a configuration of a grid-connected general photovoltaic power generation system.

Referring to FIG. 7, this solar power generation system includes solar cell modules 1A to 1C, step-up / step-down circuits 2A to 2C, and an inverter 3.

[0006] Solar cell modules 1A to 1C generate DC power from received sunlight.

The step-up / step-down circuits 2A to 2C adjust the voltage value of the DC power generated by the solar cell modules 1A to 1C to a predetermined voltage value.

[0007] Inverter 3 converts DC power received by step-up / step-down circuits 2A to 2C into AC power.

The inverter 3 then reversely flows the converted AC power to the commercial power supply 6. In other words, the AC power generated by the inverter 3 is sent to the power company's transmission line network via the commercial power supply 6. [0008] The commercial system power supply 6 supplies electric power of the power company's transmission line network to the loads 7A to 7C. Here, loads 7A-7C are household appliances, for example. The user connects the outlets 7A to 7C of home appliances to the outlet of the commercial grid power supply 6 for use.

[0009] In this solar power generation system, surplus power can be sold to an electric power company when the amount of power generated by a solar cell is larger than the amount of power consumed by home appliances, such as in the daytime on a clear day. In addition, when the amount of power generated by solar cells is less than the amount of power consumed by home appliances, such as overcast or at night, the shortage can be purchased from an electric power company. Therefore, even when the amount of power generated by the solar cell module is not sufficient, such as when it is cloudy or at night, it is possible to stably supply power to the home appliances.

FIG. 8 is a diagram showing a configuration of a stand-alone general photovoltaic power generation system.

Referring to FIG. 8, this solar power generation system includes a solar cell module 1A, a step-up / down circuit 2A, an inverter 3, and a storage battery 18.

[0011] When the power consumption of the load 7A is smaller than the AC power generated by the inverter 3, the storage battery 18 stores the DC power also received by the buck-boost circuits 2A to 2C. Further, when the power consumption of the load 7A is larger than the AC power generated by the inverter 3, the storage battery 18 discharges the stored DC power and supplies it to the inverter 3 to compensate for the shortage.

Inverter 3 converts DC power received from step-up / down circuit 2A and DC power discharged from storage battery 18 into AC power. Then, the inverter 3 supplies the converted AC power to the load 7A.

Other configurations and operations are the same as those of the photovoltaic power generation system shown in FIG. 7, and therefore description thereof will not be repeated.

Here, a photovoltaic power generation system power similar to that of the photovoltaic power generation system shown in FIG. 7 is disclosed in Japanese Patent Laid-Open No. 7-194134 (Patent Document 1). In other words, by switching a FET (Field Effect Transistor) bridge circuit using a gate pulse signal that has been PWM modulated with a sine wave, it is controlled so that a sine wave current flows through the output of the grid-connected inverter. Supply the output power of the solar cell. At this time, an error signal between the sinusoidal waveform pattern signal read from the waveform pattern storage unit and the inverter output current signal from which the current transformer force is also output is amplified by an error amplifier, and this signal is PWM (Pulse Since the PWM control is performed by the width control unit and the gate drive signal is generated by the gate drive signal generation unit, feedback control is realized so that the output current signal matches the read sine waveform pattern.

Patent Document 1: Japanese Patent Laid-Open No. 7-194134

Disclosure of the invention

Problems to be solved by the invention

However, in the grid-connected photovoltaic power generation system described in Patent Document 1 and the grid-connected photovoltaic power generation system shown in FIG. 7, all power in the home is covered by photovoltaic power generation. It was necessary to install a large number of solar cell modules, and the installation cost increased.

[0016] In addition, in the stand-alone photovoltaic power generation system shown in FIG. 8, it is necessary to enlarge the storage battery 18 in order to cover all household power with photovoltaic power generation because it is not linked to the commercial power source 6. In addition, since storage batteries have a short life, they must be replaced and maintained regularly, which increases installation costs and operation costs.

[0017] Therefore, an object of the present invention is to provide a photovoltaic power generation system capable of preventing an increase in installation cost and operation cost.

Means for solving the problem

[0018] In order to solve the above problems, a photovoltaic power generation system according to an aspect of the present invention is a photovoltaic power generation system that supplies power to a load, and is generated by a solar cell module and the solar cell module. A buck-boost circuit that adjusts the voltage value of the DC power, a rectifier circuit that converts AC power from the commercial power supply into DC power, and a DC power that has been adjusted by the buck-boost circuit and the rectifier circuit. And an inverter that generates AC power to be supplied from DC power to the load.

[0019] Preferably, the photovoltaic power generation system further lacks DC power whose voltage value is adjusted by a step-up / down circuit relative to DC power necessary to generate AC power to be supplied to a load. In such a case, the control circuit determines that the shortage of the DC power whose voltage value has been adjusted by the step-up / down circuit is compensated by the DC power converted by the rectifier circuit. When it is decided to make up for the shortfall with DC power converted by the rectifier circuit In this case, AC power from commercial power supply is converted to DC power, and the converted DC power is output to the inverter.

[0020] Preferably, the photovoltaic power generation system further includes AC power generated by an inverter and AC power from a commercial power source based on the amount of DC power whose voltage value is adjusted by a step-up / down circuit. A control circuit that selects either of these, and a control that switches between output of AC power generated by the inverter to the load or output of AC power of commercial power supply to the load based on the selection of the control circuit With a switch.

[0021] More preferably, the control circuit selects the AC power from the commercial power supply when the DC power whose voltage value is adjusted by the step-up / down circuit satisfies the following formula. PK PX (1—AXB) / A ₀ where P is the power consumption of the load, P1 is the DC power whose voltage value is adjusted by the buck-boost circuit, A is the inverter efficiency, and B is the rectifier circuit Efficiency.

[0022] More preferably, the inverter further adjusts the phase of the AC power to be converted so that it matches the phase of the AC power of the commercial power supply power when the control circuit changes the selection of the AC power. The control circuit changes the selection of AC power after the inverter performs AC power phase adjustment.

The invention's effect

[0023] According to the present invention, even a simple system consisting of a single solar cell module can be introduced as a power source for household electric appliances.

Brief Description of Drawings

FIG. 1 is a diagram showing a configuration of a photovoltaic power generation system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an electric circuit of the photovoltaic power generation system according to the embodiment of the present invention.

[Figure 3] Shows the current-voltage characteristics of solar cells.

FIG. 4 is a diagram showing power and efficiency in the photovoltaic power generation system according to the embodiment of the present invention.

FIG. 5 is a diagram showing AC power phase adjustment performed by the photovoltaic power generation system according to the embodiment of the present invention.

[FIG. 6] —A graph showing the daily power generation of a general solar cell. FIG. 7 is a diagram showing a configuration of a grid-connected general photovoltaic power generation system.

Explanation of symbols

[0025] 1A-: LC solar cell module, 2A-2C buck-boost circuit, 3 inverter, 4 control switch, 5 rectifier circuit, 10 control circuit, 11 switch, D1-D2 diode, CT1-CT2, PT1 sensor, 7A load , 8A ~ 8B Outlet, 9A ~ 9B

Cable, 18 storage batteries, 100 solar power system.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a photovoltaic power generation system 100 includes a solar cell module 1A, a step-up / down circuit 2A, an inverter 3, a control switch 4, a rectifier circuit 5, a control circuit 10, and a switch. 11, diode D1, diode D2, sensor CT1, sensor CT2, sensor PT1, outlet 8B, and cable 9A.

[0028] Since solar cell module 1A and step-up / down circuit 2A are similar to the solar power generation system shown in FIG. 7, description thereof will not be repeated here.

[0029] The switch 11 rectifies the AC power received from the commercial power supply 6 in the on state.

Output to 5 and stop the output of AC power received from commercial power supply 6 in the off state.

The rectifier circuit 5 converts AC power from the commercial power supply 6 into DC power and outputs it to the inverter 3.

[0031] The diode D1 and the diode D2 prevent backflow of the output currents of the step-up / step-down circuit 2A and the rectifier circuit 5.

Inverter 3 converts the DC power received from step-up / step-down circuit 2 A and the DC power received from rectifier circuit 5 into AC power, and outputs the converted AC power to control switch 4.

[0033] Based on a control signal received from a control circuit 10 to be described later, the control switch 4 generates a power for outputting the AC power generated by the inverter 3 to the load 7A or the AC power from the commercial power source 6. Switches whether to output to load 7A. The sensor CT1 measures a current output to the step-up / step-down circuit 2A force inverter 3. Sensor PT1 measures the voltage output to step-up / down circuit 2A force inverter 3. Sensor CT2 measures the load current, that is, the current output by inverter 3 to load 7A. The control circuit 10 receives the measurement result of each sensor, and outputs the DC power adjusted from the voltage value output from the step-up / down circuit 2A and the power consumption of the load, that is, the AC power to be supplied to the load 7A. (Hereinafter referred to as target AC power).

[0035] The control circuit 10 uses DC power output from the step-up / step-down circuit 2A due to cloudy weather or the like to generate target AC power (hereinafter referred to as target DC power). If the target AC power generated by the inverter 3 is less efficient than using the AC power from the commercial power supply 6 directly, the rectifier circuit 5 can compensate for the shortage relative to the target DC power. Decide to make up for the DC power to be converted. In this case, the control circuit 10 selects the AC power generated by the inverter 3 and outputs a control signal representing the selection result to the control switch 4. Further, in this case, the control circuit 10 performs control to turn on the switch 11 and supply AC power from the commercial power supply 6 to the rectifier circuit 5.

[0036] Further, because of the cloudy weather, the control circuit 10 has a DC power output from the step-up / step-down circuit 2A smaller than the target DC power, and the inverter 3 does not generate the target AC power. If it is more efficient to use the AC power directly from 6, the AC power from the commercial power supply 6 is selected and a control signal representing the selection result is output to the control switch 4. In this case, the control circuit 10 performs control to turn off the supply of AC power from the commercial power supply 6 to the rectifier circuit 5 by turning off the switch 11. For example, when the power generation amount of the solar cell module 1A cannot be obtained at all, such as at night, the control circuit 10 selects the AC power from the commercial power source 6. With this configuration, AC power from the commercial power supply 6 is output to the load 7A without passing through the rectifier circuit 5 and the inverter 3, thus avoiding losses caused by power conversion in the rectifier circuit 5 and the inverter 3. can do.

[0037] On the other hand, when the DC power output from the step-up / down circuit 2A is larger than the target DC power, the control circuit 10 performs control to limit the DC power supplied from the step-up / down circuit 2A to the inverter 3 . In this case, the control circuit 10 turns off the switch 11 and turns off the commercial power supply. Control to stop the supply of AC power from 6 to rectifier circuit 5 is performed.

[0038] When the DC power output from the step-up / step-down circuit 2A and the target DC power are equal, the control circuit 10 selects the AC power generated by the inverter 3 and outputs a control signal representing the selection result. Output to control switch 4. In this case, the control circuit 10 performs control to turn off the supply of AC power from the commercial power supply 6 to the rectifier circuit 5 by turning off the switch 11.

[0039] Next, an operation when each circuit is controlled based on the output DC power will be described in the control circuit 10 power step-up / step-down circuit 2A power in the photovoltaic power generation system according to the embodiment of the present invention.

[0040] FIG. 2 is a diagram showing an electric circuit of the photovoltaic power generation system according to the embodiment of the present invention.

Referring to FIG. 2, DC power supply E1 represents a DC voltage on the step-up / down circuit 2A side, and DC power supply E2 represents a DC voltage on the rectifier circuit 5 side. The DC power supply E1 and the current limiting resistor rl correspond to the step-up / down circuit 2A, and the DC power supply E2 and the current limiting resistor r2 correspond to the rectifier circuit 5. In FIG. 2, for the sake of simplicity, the conversion from DC power to AC power in the inverter 3 is omitted, and DC power is directly supplied to the load 7A.

[0042] The current II is a current supplied to the inverter 3 from the step-up / down circuit 2A. The current 12 is a current supplied from the rectifier circuit 5 to the inverter 3.

[0043] Resistance values of the current limiting resistor rl and the current limiting resistor r2 change based on control from the control circuit 10.

[0044] The load current flowing through the load 7A becomes 1 = 11 +12, and the load voltage applied to the load 7A V = R

X I and power consumption of load 7A P = RX I2.

[0045] The control circuit 10 monitors the load voltage V measured by a sensor (not shown), and increases or decreases the load current I so as to keep the load voltage V constant, that is, the inverter 3 generates target AC power. By performing the control, the load is stably operated.

FIG. 3 shows the current-voltage characteristics of the solar cell.

Referring to Fig. 3, when the amount of light received by the solar cell is small, the output current and output voltage from the solar cell become small. In this case, the control circuit 10 first sets the current limiting resistance rl. Control to increase the current II by decreasing the resistance value. The control circuit 10 reduces the AC power generated by the inverter 3 below the target AC power even if the current II is increased by decreasing the resistance value of the current limiting resistor rl, and the target AC power is output by the inverter 3. If the power generation is more efficient than the direct use of AC power from the commercial grid power supply 6, control is performed to increase the current 12 by reducing the resistance value of the current limiting resistor r2. In other words, the shortage of the DC power output from the step-up / down circuit 2A with respect to the target DC power is supplemented with the DC power converted by the rectifier circuit 5.

[0047] On the other hand, when the amount of light received by the solar cell is large, the output current and output voltage from the solar cell increase. In this case, the control circuit 10 first performs control to limit the current 12 by increasing the resistance value of the current limiting resistor r2.

[0048] Then, the control circuit 10 has a current 12 = 0, that is, when the AC power generated by the inverter 3 is larger than the target AC power even when the supply of DC power from the rectifier circuit 5 to the inverter 3 is stopped. Controls the current II by increasing the resistance value of the current limiting resistor rl. The control circuit 10 stops the supply of AC power from the commercial power supply 6 to the rectifier circuit 5 by turning off the switch 11 instead of increasing the resistance value of the current limiting resistor r2 and setting the current 12 = 0. You can control it.

[0049] Next, the operation when switching the selection of the AC power generated by the control circuit 10-power inverter 3 and the AC power from the commercial power source 6 in the photovoltaic power generation system according to the embodiment of the present invention Will be described.

[0051] Referring to FIG. 4, the amount of AC power supplied to load 7A, that is, the power consumption of load 7A is Po, and the amount of DC power output from buck-boost circuit 2A is P1, Assume that AC power received by rectifier circuit 5 from commercial power supply 6 is P2, AC power received by control switch 4 from commercial power supply 6 is P3, inverter 3 efficiency is A, and rectifier circuit 5 efficiency is B. When the control switch 4 outputs the AC power generated by the inverter 3 to the load 7A, Po is expressed by the following equation.

[0052] 0052ο = Α Χ Ρ1 + ΑΧ Β Χ Ρ2 ... (A1) On the other hand, when the control switch 4 outputs AC power from the commercial power supply 6 to the load 7A, Po is expressed by the following equation.

[0053] Ρο = Ρ3 · · · · (Α2)

Here, when the amount of DC power output from the buck-boost circuit 2 is reduced, the control circuit 10 performs control to compensate for the shortage relative to the target DC power with the DC power received from the rectifier circuit 5 as described above. In addition, the amount of DC power received by inverter 3 from rectifier circuit 5 increases. If the AC power Ρ2 output from the commercial power supply 6 to the rectifier circuit 5 exceeds the AC power Ρ3 output from the commercial power supply 6 to the control switch 4, the target AC power is not generated by the inverter 3. Therefore, it is more efficient to use AC power directly from the commercial power source 6 for the power supply! Therefore, the control circuit 10 selects the AC power generated by the inverter 3 from the AC power generated by the inverter 3 to the AC power from the commercial power source 6. The condition for switching is expressed by the following formula.

[0054] Ρ3 <Ρ2 · · · (A3)

Equation (A1) Equation (Α2) and Equation (A3) Forces are also obtained by eliminating Ρ2 and Ρ3.

[0055] ΡΚ Ρο Χ (1 -Α Χ Β) / Α · · · (Α4)

Therefore, the control circuit 10 determines that the AC power generated by the inverter 3 is AC power from the commercial power source 6 when the amount of DC power P1 output from the step-up / step-down circuit 2Α satisfies the formula (Α4). Switch the selection to. With such a configuration, it is possible to improve the power use efficiency in the photovoltaic power generation system.

Next, the operation when the photovoltaic power generation system according to the embodiment of the present invention switches the selection between the AC power generated by the inverter 3 and the AC power from the commercial power supply 6 will be described.

FIG. 5 is a diagram showing phase adjustment of AC power performed by the solar power generation system according to the embodiment of the present invention.

Referring to FIG. 5, the waveforms of (1) and (4) are the AC power on the inverter side, that is, the waveform of the AC power that control switch 4 receives from inverter 3, and the waveforms of (2) and (5) The waveform is the AC power on the commercial power supply side, that is, the AC power waveform received by the control switch 4 from the commercial power supply 6.The waveforms in (3) and (6) are the AC power output from the control switch 4. It is a waveform.

[0059] The waveforms of (1) and (2) are 90 degrees out of phase. Here, simply switching the output of control switch 4 from AC power of (1) to AC power of (2) at time tl, the waveform of AC power output from control switch 4 is as shown in (3) It becomes a discontinuous waveform, causing problems such as an abnormal current flowing instantaneously from control switch 4.

Therefore, in the photovoltaic power generation system according to the embodiment of the present invention, the control circuit 10 issues a phase adjustment command when switching between the AC power on the inverter side and the AC power on the commercial system power supply side. Output to inverter 3.

[0061] Inverter 3, in response to the phase adjustment command from control circuit 10, receives the AC power to be output to control switch 4 so that the phase of the AC power on the inverter side matches the phase of the AC power on the commercial power supply side. Adjust the phase as shown in (4).

[0062] Then, after the inverter 3 adjusts the phase of the AC power, the control circuit 10 changes the selection from the AC power on the inverter side to the AC power on the commercial power supply side at time tl, and the selection result Is output to control switch 4.

[0063] As a result, the waveform of the AC power output from the control switch 4 becomes a continuous waveform as shown in (6) even before and after switching, so that an abnormal current and an instantaneous power failure occur in the control switch 4. Can prevent household appliances with a load of 7A from operating constantly. Therefore, the photovoltaic power generation system according to the embodiment of the present invention can be used for precision equipment such as a computer.

[0064] Although the case where the control circuit 10 switches the selection from the AC power on the inverter side to the AC power on the commercial system power supply side has been described here, the control circuit 10 is switched from the AC power on the commercial system power supply side to the inverter side. The same applies to the case of switching the selection to other AC power. In other words, the phase of the AC power output from inverter 3 to control switch 4 is adjusted as shown in (4) .After the AC power phase is adjusted by control circuit 10-power inverter 3, the AC power from the commercial power supply side is changed to the inverter side By changing the selection to AC power, it is possible to prevent abnormal current from occurring in the control switch 4 and to operate the home appliance with the load 7A stably at all times.

Incidentally, the grid-connected solar power generation system described in Patent Document 1 and the system shown in FIG. In the grid-connected solar power generation system, it is necessary to install a large number of solar cell modules in order to cover all household power with solar power generation, which increases the installation cost.

[0066] In addition, in the stand-alone photovoltaic power generation system shown in FIG. 8, the storage battery 18 needs to be enlarged in order to cover all household power with photovoltaic power generation because it is not connected to the commercial power source 6. In addition, since storage batteries have a short life, they must be replaced and maintained regularly, which increases installation costs and operation costs.

However, in the photovoltaic power generation system according to the embodiment of the present invention, the rectifier circuit 5 converts AC power from the commercial power supply 6 into DC power and outputs it to the inverter 3. Then, the inverter 3 converts the DC power received from the rectifier circuit 5 and the DC power generated by the solar cell module 1A received via the step-up / down circuit 2A into AC power. With such a configuration, it is not necessary to cover all household power with photovoltaic power generation, so there is no need to install a large number of solar cell modules, and there is no need to install storage batteries.

[0068] Therefore, in the photovoltaic power generation system according to the embodiment of the present invention, an increase in installation cost and operation cost can be prevented.

[0069] In the photovoltaic power generation system according to the embodiment of the present invention, control circuit 10 turns off switch 11 when the DC power output from step-up / down circuit 2A is equal to or higher than the target DC power. As a state, control is performed to stop the supply of AC power from the commercial power supply 6 to the rectifier circuit 5. Therefore, it is possible to prevent the AC power from the commercial power supply 6 from being wasted and to improve the power usage efficiency.

[0070] In the grid-connected solar power generation system described in Patent Document 1 and the grid-connected solar power generation system shown in Fig. 7, even when a small number of solar cell modules are installed, the solar power generation system Because it is necessary to apply to a power company etc. to connect (connect) to the commercial power supply and install it in a contractor with a predetermined qualification, the user can easily install it like a general household appliance. In addition, there is a problem that it cannot be removed.

However, in the photovoltaic power generation system according to the embodiment of the present invention, the AC power from the commercial power source 6 is supplied to the photovoltaic power generation system by connecting the cable 9A to the household outlet 8A. Connect the cable 9B of the home appliance with a load of 7A. By connecting the solar cell module 1A to a place where the sun hits, connecting to the cent 8B, AC power from the photovoltaic power generation system is supplied to the household electrical appliance with the load 7A. Therefore, in the photovoltaic power generation system according to the embodiment of the present invention, a user who does not need to be connected to the commercial power supply 6 can easily install and remove.

[0072] Further, in the photovoltaic power generation system according to the embodiment of the present invention, the DC power output from the step-up / down circuit 2A with respect to the target DC power is converted by the rectifier circuit 5, that is, the DC power. By supplementing with AC power from the commercial power supply 6, even a single solar cell module can stably supply power to the load. Therefore, the photovoltaic power generation system according to the embodiment of the present invention can be installed in a narrow space such as a veranda, and can also be used for loads that regularly consume power regardless of day or night, such as a refrigerator. Can be used.

[0073] The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims

The scope of the claims

[1] A photovoltaic power generation system (100) for supplying power to a load (7A),

Solar cell module (1 A),

A step-up / down circuit (2A) for adjusting the voltage value of the DC power generated by the solar cell module (1A);

A rectifier circuit (5) for converting AC power from a commercial power supply (6) into DC power, and DC power whose voltage value is adjusted by the step-up / down circuit (2A) and converted by the rectifier circuit (5) A photovoltaic power generation system comprising an inverter (3) that generates AC power to be supplied from DC power to the load (7A).

[2] The solar power generation system (100) further includes:

When the DC power whose voltage value is adjusted by the step-up / down circuit (2A) is insufficient with respect to the direct-current power required to generate the AC power to be supplied to the load (7A), the step-up / step-down circuit A control circuit (10) for deciding to compensate for the shortage of DC power whose voltage value is adjusted by the circuit (2A) with DC power converted by the rectifier circuit (5);

The rectifier circuit (5), when the control circuit (10) decides to supplement the shortage of the DC power with the DC power converted by the rectifier circuit (5), the commercial power supply ( 6) The photovoltaic power generation system according to claim 1, wherein the AC power is converted into DC power, and the converted DC power is output to the inverter (3).

[3] The photovoltaic power generation system (100) further includes:

Based on the amount of DC power whose voltage value is adjusted by the step-up / down circuit (2A), the AC power generated by the inverter (3) and the AC power from the commercial power supply (6) A control circuit (10) that selects either of!

Based on the selection of the control circuit (10), the AC power generated by the inverter (3) is output to the load (7A), or the AC power from the commercial power supply (6) is The photovoltaic power generation system according to claim 1, further comprising a control switch (4) for switching whether to output to the load (7A).

[4] The control circuit (10) selects the AC power from the commercial power supply (6) when the DC power whose voltage value is adjusted by the step-up / down circuit (2A) satisfies the following equation: Contract The photovoltaic power generation system according to claim 3.

PK P X (1 -AX B) / A

Where P is the power consumption of the load (7A), P1 is the DC power whose voltage value is adjusted by the buck-boost circuit (2A), A is the efficiency of the inverter (3), and B is This is the efficiency of the rectifier circuit (5).

Further, when the control circuit (10) changes the selection of the AC power, the inverter (3) further converts the conversion so as to match the phase of the AC power from the commercial power supply (6). Adjust the phase of AC power to

The photovoltaic power generation system according to claim 3, wherein the control circuit (10) changes the selection of the AC power after the inverter (3) performs phase adjustment of the AC power.