JP2014023317A - Photovoltaic power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photovoltaic power generation system capable of preventing an excessive load from being applied to an apparatus by reducing unnecessary power consumption.SOLUTION: A photovoltaic power generation system 10 includes: a solar cell array 12; an inverter device 14 that converts DC power output from the solar cell array 12 into AC power; and a transformer 16 that is connected with an inverter device 14 and converts to a predetermined voltage. The photovoltaic power generation system 10 further includes a feeding stop system 18 that controls connection and disconnection with/from a power system.

Description

  The present invention relates to a photovoltaic power generation system that is grid-connected to a power transmission network.

  In recent years, solar power generation has been actively developed, and large-scale solar power generation systems of 1 MW or more have also been developed. A conventional photovoltaic power generation system 100 shown in FIG. 2 includes a solar cell array 12 and an inverter device (power conditioner) 14 that converts DC power output from the solar cell array 12 into AC power. The inverter device 14 is connected to a commercial power system (power transmission network) via the transformer 16 and the like, and the power generated by the solar cell array 12 is sent to the commercial power system.

  The inverter device 14 includes a DC-DC converter that is controlled by MPPT (Maximum Power Point Tracking) and an inverter circuit that outputs AC power. Each of these circuits is driven by a control circuit.

  In order to drive the control circuit included in the inverter device 14, power is obtained from the power system. Therefore, if the power generation amount of the solar cell array 12 does not exceed the power consumption of the inverter device 14, the power consumption is the same as the simple power consumption.

  No power is generated by the solar cell array 12 at night. Moreover, even if it is daytime, if the amount of solar radiation is small, the solar cell array 12 will not generate electric power. Even in such a case, it is necessary to obtain power from a commercial power system in order to drive the inverter device 14. This is unnecessary power consumption and should be avoided. In the solar power generation system 100 of about 20 MW, the fee for purchasing electricity during the non-power generation time is about 6 million yen per year, and the economic loss is large.

  As a countermeasure, it is conceivable to install a circuit breaker between the photovoltaic power generation system 100 and the power system as in Patent Document 1 below. The circuit breaker is controlled by a timer. In the morning, the circuit breaker connects the photovoltaic power generation system 100 and the power system. At night, the circuit breaker disconnects the photovoltaic power generation system 100 from the power system. Power is not obtained from the power grid at night when power generation is not performed.

  However, in the case of Patent Document 1, an inrush current flows through the transformer 16 every time the circuit breaker connects the solar power generation system 100 and the power system. The transformer 16 used in the electric power system is expensive, and it is a problem to deteriorate such a transformer 16 by applying an extra load. In addition, the load on the breaker is large, and the number of times the breaker is used decreases. When an inrush current flows, there is a possibility that an instantaneous voltage drop of the power system may occur, and the power system becomes unstable. Furthermore, in the case of Patent Document 1, since it is controlled by a timer, it is necessary to obtain power from a commercial power system on days when the amount of solar radiation is small, and unnecessary power consumption occurs.

JP-A-6-197455

  An object of the present invention is to provide a photovoltaic power generation system that reduces unnecessary power consumption and does not place a load on an apparatus.

  The solar power generation system is connected to the power system. The configuration includes a solar cell array, an inverter device that converts DC power output from the solar cell array into AC power, a transformer that is connected to the inverter device and converts it to a predetermined voltage, and a power supply stopping system. Is provided.

  The power supply stop system includes a first circuit breaker provided between the power system and a transformer, a generator, a second circuit breaker provided between the generator and the transformer, and the power system. And a generator that synchronizes with the generator and opens and closes the first breaker and the second breaker, a starter that controls the output voltage of the generator, and the amount of solar radiation where the solar cell array is located And a calculation circuit that transmits a start signal to the synchronous detector and the starter when the amount of solar radiation detected by the pyranometer reaches a predetermined value.

  When the solar cell array is generating power, the first circuit breaker is closed and power is transmitted to the power system. When solar radiation becomes a predetermined value or less and no power is generated by the solar cell array, the first circuit breaker is opened, and power supply from the power system to the inverter device is stopped.

  When the solar radiation again exceeds a predetermined value, the second circuit breaker is closed, the generator is driven, and power is supplied to the inverter device. The generator and the power system are synchronized, and if the synchronization is established, the first breaker is closed. Then, a 2nd circuit breaker is open | released and a generator is stopped.

  The starter is a soft starter and controls the output voltage of the generator to gradually become a predetermined voltage. The generator is a synchronous generator.

  According to the present invention, the power is not consumed by the control module or the like when no power is generated by the solar cell array at night or the like. There is no wasteful power consumption and the environmental load can be reduced. Inrush current can be suppressed when connecting to the power system, reducing the load on the equipment and extending the service life.

It is a figure which shows the structure of the solar energy power generation system of this invention. It is a figure which shows the structure of the conventional solar power generation system.

  The photovoltaic power generation system of the present invention will be described with reference to the drawings. The solar power generation system is connected to a commercial power system, and supplies power to the power system during power generation.

  A solar power generation system 10 illustrated in FIG. 1 includes a solar cell array 12, an inverter device 14 that converts DC power output from the solar cell array 12 into AC power, and a transformer 16 that converts the DC power into a predetermined voltage. Moreover, the solar power generation system 10 includes a power supply stopping system 18 that controls connection and disconnection to the power system.

  The solar cell array 12 has a plurality of solar cell panels attached to a rectangular frame. On the back side of the solar cell panel, wiring and the like are performed, and electric power is output from the solar cell panel. The power output from one solar cell array 12 is about 300 W, for example. The solar cell array 12 is fixed to a gantry fixed to the ground or the roof. Although one solar cell array 12 is shown in FIG. 1, a plurality of solar cell arrays 12 may be connected.

  The inverter device 14 includes a circuit that performs MPPT control and an inverter circuit that converts DC power into AC power. In order to perform MPPT control, a circuit for measuring the output voltage and current of the solar cell array 12, a DC-DC converter, and a circuit for MPPT control of the DC-DC converter from the output voltage and current are provided. The power extraction efficiency of the solar cell array 12 is increased.

  The inverter circuit includes a switching element (power semiconductor) for power control and a circuit for controlling switching, and outputs AC power by switching. The control circuit included in the inverter device 14 obtains power from a commercial power system. A transformer 16 is connected to the inverter device 14 and is converted into a desired voltage by the transformer 16.

  You may insert the power factor improvement apparatus 20 between the transformer 16 and an electric power grid | system. As the power factor correction device 20, a power capacitor or the like is used. The power factor of the no-load current of the transformer 16 is very bad, and the capacity of the generator 22 can be reduced by the power factor improving device 20.

  The power supply stopping system 18 includes a generator 22, a first circuit breaker SW1 provided between the power system and the transformer 16, a second circuit breaker SW2 provided between the generator 22 and the transformer 16, and solar radiation. A total 24 and a control device 26 are provided. The power supply stopping system 18 prevents the inverter device 14 from consuming electric power when the solar cell array 12 is not generating power at night or the like.

  Examples of the generator 22 include a synchronous generator driven by a prime mover 28. After generating electricity with the generator 22 and supplying electric power to the inverter device 16, electric power is supplied to the inverter device 16 from the power system.

  The first circuit breaker SW <b> 1 and the second circuit breaker SW <b> 2 are switches that connect or disconnect the power system or the generator 22 with respect to the transformer 16. Supply and stop of power to the inverter device 16 are switched by the first breaker SW1 and the second breaker SW2. Since the inrush current to the transformer 16 is suppressed as described below, the load on each breaker SW1, SW2 is small, and the number of times each breaker SW1, SW2 can be opened and closed can be increased.

  An example of the pyranometer 24 is a device that uses a thermoelectric element. In the thermoelectric element, an electromotive force is generated from thermal energy generated by solar radiation, and the amount of solar radiation is obtained from the electromotive force. The pyranometer 24 is disposed adjacent to the solar cell array 12. When the solar radiation meter 24 is irradiated with sunlight, the solar cell array 12 is also irradiated with sunlight. Whether or not the solar cell array 12 can generate power is checked by the pyranometer 24.

  The control device 26 includes a synchronous detector 30, a starter 32 that controls the output voltage of the generator 22, an arithmetic circuit 34 that transmits a signal to the synchronous detector 30 and the starter 32, and a speed adjuster 36 that adjusts the speed of the prime mover 28. Is provided. These are composed of circuits and programs that operate as described later.

  The synchronization detector 30 synchronizes the power system and the generator 22 and sends an open / close signal to the first breaker SW1 and the second breaker SW2. The voltage and phase of the power system and the generator 22 are matched by the synchronization detector 30, and the connection from the generator 22 to the power system can be switched.

  The starter 32 is a soft starter. The output voltage of the generator 22 is gradually increased to a predetermined value. A soft starter circuit including a thyristor and a switch is inserted into the output of the generator 22, and a control signal is sent from the starter 32 to the thyristor and the switch to perform a soft start. The voltage is gradually increased after applying no voltage without applying all voltage. The magnetizing inrush current to the transformer 16 is suppressed.

  The arithmetic circuit 34 receives the solar radiation amount data from the solar radiation meter 24, and transmits a start signal or a stop signal to the synchronous detector 30 and the starter 32 when it reaches a predetermined value. The arithmetic circuit 34 is configured by a circuit such as a CPU (Central Processing Unit).

  The speed adjuster 36 adjusts the speed of the prime mover 28 so that the output voltage and frequency of the generator 22 become predetermined values. In order to synchronize the power system and the generator 22, the speed adjuster 36 is driven by a command from the synchronization detector 30.

  The power supply to the control device 26 and the pyranometer 24 may be performed from the power system, or the power generated by the solar cell array 12 is stored in a power storage means such as a secondary battery or an electric double layer capacitor. You may utilize those electric powers. Further, the power stored in the power storage means may use power from the power system. A primary battery may be used instead of the power storage means. The electric power consumed by the inverter device 16 is very small, and the electric power can be reduced as compared with the prior art.

  Next, the operation of the solar power generation system 10 will be described. Suppose that the solar cell array 12 is irradiated with sunlight in the daytime. At this time, the first breaker SW1 is closed and the second breaker SW2 is open. The electric power generated by the solar cell array 12 is sent to the electric power system. The generator 22 is stopped.

  (1) When the amount of solar radiation to the pyranometer 24 falls below a predetermined value due to sunset, a stop signal is sent from the arithmetic circuit 34 to the synchronous detector 30. The first circuit breaker SW1 is opened by a signal from the synchronization detector 30. Since the solar radiation amount is less than or equal to the predetermined value, the solar cell array 12 cannot generate power that can be output to the power system. The transformer 16 and the power system are disconnected, and there is no power supply from the power system. There is no unnecessary power consumption in the inverter device 14.

  In addition, even if it is daytime, when the solar cell array 12 does not perform predetermined power generation due to cloudy weather or rainy weather, the first circuit breaker SW1 is opened, and the power system and the transformer 16 are disconnected.

  (2) When sunrise occurs and the amount of solar radiation to the pyranometer 24 reaches a predetermined value, an activation signal is sent from the arithmetic circuit 34 to the synchronous detector 30. A start signal is sent from the synchronous detector 30 to the speed adjuster 36, the prime mover 28 is started by the speed adjuster 36, and the output frequency of the generator 22 is raised to the rated frequency.

  (3) When the output of the generator 22 reaches the rated frequency, the second breaker SW2 is closed. The generator 22 and the transformer 16 are connected.

  (4) An activation signal is also sent from the arithmetic circuit 34 to the starter 32, and the output of the generator 22 gradually rises to a specified value (soft start) by the starter 32. The inrush current to the transformer 16 is suppressed by the soft start.

  (5) When the output of the generator 22 reaches a predetermined frequency and voltage, the synchronization detector 30 and the speed adjuster 36 synchronize with the voltage and phase of the power system.

  (6) When the synchronization is established, the first circuit breaker SW1 is closed. A transformer 16 is connected to the power system. The electric power system and the generator 22 are synchronized, and the combined operation becomes possible.

  (7) When the first circuit breaker SW1 is closed and the power supply system receives no-load loss, the second circuit breaker SW2 is opened. The generator 22 is disconnected from the transformer 16 and the switching to the power system is completed.

  (8) The prime mover 28 is stopped by the speed adjuster 36 and the power generation of the generator 22 is stopped. When the solar cell array 12 is generating power and sunset occurs, the process returns to the above step (1).

  As described above, the present invention has a configuration in which power is not consumed by the inverter device 14 when power is not generated by the solar cell array 12 at night or the like. There is no wasteful power consumption and the environmental load can be reduced. Inrush current can be suppressed when connecting to the power system, reducing the load on the equipment and extending the service life.

  Although the embodiments of the present invention have been described, the present invention is not limited to the above-described embodiments. For example, the solar power generation system 10 is not limited to a large-scale power plant, and may be a small-scale solar power generation system 10 in each household.

  In addition to connecting the solar power generation system 10 to a commercial power system, it may be connected to a power system for private consumption in a large-scale plant or the like.

  In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

10: Photovoltaic power generation system 12: Solar cell array 14: Inverter device 16: Transformer 18: Power supply stop system 20: Power factor improvement device 22: Generator 24: Solar radiation meter 26: Control device 28: Motor 30: Synchronous detector 32: Starter 34: Arithmetic circuit 36: Speed controller

Claims (3)

A solar power generation system connected to an electric power system,
A solar cell array,
An inverter device for converting DC power output from the solar cell array into AC power;
A transformer connected to the inverter device and converting it to a predetermined voltage;
A first circuit breaker provided between the power system and the transformer;
A generator,
A second circuit breaker provided between the generator and the transformer;
A synchronization detector that synchronizes the power system and the generator and opens and closes the first breaker and the second breaker;
A starter for controlling the output voltage of the generator;
A pyranometer for detecting the amount of solar radiation at the place where the solar cell array is disposed;
An arithmetic circuit that transmits a start signal to the synchronous detector and the starter when the amount of solar radiation detected by the pyranometer reaches a predetermined value;
Solar power generation system equipped with. The solar power generation system according to claim 1, wherein the starter is a soft starter and controls the output voltage of the generator to gradually become a predetermined voltage. The solar power generation system according to claim 1 or 2, wherein the generator is a synchronous generator.

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