JPH0772942A - Power supply system start-up/stoppage controller - Google Patents

Abstract

PURPOSE:To stably perform the start-up and stoppage of a power supply system at the time of low quantity of solar radiation in which the start-up operation and stopping operation of the power supply system tend to be performed frequently and repeatedly. CONSTITUTION:This controller is constituted of a detecting part 15 which detects the output of a solar battery 1, a maximum power point tracking part 16 which decides the maximum power point of the solar battery from an output voltage, a sine wave pattern control part 17 which generates a sine wave pattern for the control of an inverter 2, a sine wave pattern adjusting part 18 which switches the operation of the sine wave pattern control part 17 and a system start-up/stoppage control part 19 which performs the start-up/stoppage of a system by a prest value for system start-up/stoppage, and when a value exceeds a sine wave pattern adjusting setting preset value set so as to satisfy a condition preset value for system stoppage < preset value for sine wave pattern adjustment < preset value for system start-up, the sine wave pattern which becomes the maximum power point is outputted by the sine wave pattern control part 17, also, when it is reduced lower then that, the sine wave pattern to evade the reduction to be lower than the preset value for system stoppage is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for converting DC power output from a solar cell into AC power by a current control type inverter and controlling start and stop of a power supply system for supplying power to a load.

[0002]

2. Description of the Related Art In solar power generation systems, in Japan, solar cells are installed on the roofs of individual houses, etc., due to the fact that the commercial power grid is complete and the land area used by solar cells is a problem. A grid-connected solar power generation system that connects such a solar power generation system to a commercial power system is considered promising.

FIG. 2 shows an example of a grid-connected photovoltaic power generation system which is an example of a power supply system. The DC power output from the solar cell 1 is converted into AC power by the inverter 2 and supplied to the commercial power system 3 and the load 4. An interconnection relay 5 is provided between the inverter 2 and the commercial power system 3 to perform interconnection with and disconnect from the commercial power system. A backflow prevention diode 6, a DC capacitor 7 that suppresses fluctuations in input power to the inverter 2, and a DC input current detection CT 8 are connected to the output terminal of the solar cell 1. The system control circuit 14 controls the solar cell operating point from the DC voltage and the DC current, and controls the start and stop of the grid interconnection system. As a method of controlling the operating point of the solar cell, control is performed by assuming that the voltage at the operating point that extracts the maximum power is constant, or tracking the maximum power point in order to use the output power of the solar cell more effectively. The method etc. are used.

In the grid interconnection system, the inverter 2 is stopped and the grid interconnection relay 5 is operated when the grid interconnection system side or the commercial power grid side is abnormal or when the amount of solar radiation at night is zero.
To disconnect the system interconnection system from the commercial power system, and when the normal state recovers from an abnormality or when the amount of solar radiation rises from zero at dawn, the inverter 2 is started and The relay 5 is turned on to connect the grid interconnection system to the commercial power grid.

Conventionally, the system interconnection system is started and stopped when the DC voltage of the DC capacitor 7 at the output end of the solar cell 1 exceeds the set value for start and falls below the set value for stop. I was going to stop. However, at low insolation, such as in the morning and in the evening,
The DC voltage of the DC capacitor 7 may fall below the stop set value, and even if the stop is reached once, the solar cell open-circuit voltage is equal to or higher than the start set value at that time.
There is a problem in that the system is immediately started up, and the stop operation and the start-up operation are frequently repeated, which adversely affects the reliability of the device.

In order to solve this problem, for example, as shown in JP-A-64-1480, a DC capacitor 7
Instead of immediately starting when the DC voltage of the power supply exceeds the set value for start-up, or stopping immediately when it falls below the set value for stop, a delay time is provided to respond to fluctuations in solar radiation And a method for stopping, and Japanese Patent Laid-Open No. 2-1
In the 56313, as shown in FIG. 3, the DC side relay 21 is provided in parallel with the output end of the solar cell 1, the DC side relay 21 is closed when the inverter 2 is stopped, and the output of the solar cell 1 is measured by the short-circuit current. When there is a sufficient solar cell output, the method of opening the DC side relay 21 to start the inverter 2 and turning on the interconnection relay 5 to operate the interconnection system is adopted.

[0007]

However, in the former method, the problem cannot be solved by only slightly reducing the number of times of starting and stopping, and in the latter method,
Since the solar cell output is directly measured, the problem of repeating the stop operation and the start operation is avoided, but the DC-side relay 21 itself involves mechanical operation, and the DC-side relay 21 becomes large. However, there is a problem in that cost and size are seriously hindered.

Further, when the maximum power point tracking method is used to control the operating point of the solar cell, the vicinity of the maximum power point on the solar cell output curve becomes gentle when the amount of solar radiation is low, and the detection accuracy of the maximum point deteriorates. Therefore, there is a problem that the set value for stopping the system may be temporarily lowered, but such a problem cannot be avoided by the means described above.

In order to solve these problems, the present invention aims to effectively utilize the solar cell output when the amount of solar radiation is low, by suppressing the repetition of the start and stop operations of the power supply system without using a mechanical actuator. At the same time, it is an object of the present invention to provide a control device that stably starts and stops the power supply system.

[0010]

According to the present invention, DC power output from a solar cell is converted into AC power by a current control type inverter, and the start and stop of a power supply system that supplies power to a load is controlled. Of the solar cell, the detection unit for detecting the DC voltage and DC current of the solar cell, the maximum power point tracking unit for determining the solar cell maximum power point from the DC voltage and DC current detected by the detection unit, and an inverter. The signal from the sine wave pattern control unit that generates the sine wave pattern that serves as the reference signal for control, the sine wave pattern adjustment unit that switches the operation of the sine wave pattern control unit, and the signal from the detection unit are the settings for system startup. When the value exceeds the value, the system is started, and when the value is below the set value for system stop, the system start / stop control unit that stops the system. The turn adjuster detects the signal from the detector, and the detected signal falls below the set value for sine wave pattern adjustment set so that the set value for system stop <the set value for sine wave pattern adjustment <the set value for system startup. If the adjustment operation signal is input to the sine wave pattern control unit, and if the setting value for adjusting the sine wave pattern is exceeded, the tracking operation signal is input to the sine wave pattern control unit. When the tracking operation signal is received, the sine wave pattern that maximizes the output of the solar cell is output, and when the adjustment operation signal is received, the sine wave pattern immediately before is output regardless of the maximum power point. A power supply system stop / start control device characterized by outputting a sine wave pattern having a small fixed amplitude is provided.

As the signal of the detection unit, the current and voltage values may be used as they are, or may be converted into a signal that allows the current and voltage values to be understood. As a method of generating a sine wave pattern in the sine wave pattern control unit, for example, a method of pre-storing a plurality of sine wave patterns of different amplitudes in a memory and reading the sine wave pattern, or a basic sine wave pattern There is a method of generating a sine wave pattern by multiplying the pattern by an amplitude value. The sine wave pattern with a small predetermined amplitude output during the adjustment operation means that the operating point of the solar cell is moved to the open-circuit voltage side, and the amplitude value is sufficient to exceed the set value for sine wave pattern adjustment again. Is a sine wave pattern with a small value. Stopping and starting the system means starting and stopping the inverter, and connecting and disconnecting a relay to a load that supplies electric power. As a method of outputting a sine wave pattern in which the output from the solar cell is maximized, for example, a sine wave pattern prepared in advance is sequentially output, and the output of the solar cell at that time is maximized. There is a way to find it.

The load is a device that uses an alternating current,
It may be a commercial power system or another existing power system, which may be connected independently or may be connected to a plurality.

[0013]

In the present invention, the setting value of the DC voltage is set according to the relation of "set value for system stop <set value for sine wave pattern adjustment <set value for system startup", so that the amount of solar radiation is reduced in the evening. As the operating point voltage of the solar cell, which is tracking near the maximum point, gradually decreases and falls below the set value for sine wave pattern adjustment, the sine wave pattern adjustment unit forcibly adjusts the amplitude of the sine wave pattern. The signal is generated so as to generate another sinusoidal pattern that is reduced by a fixed amount. With this signal, in the sine wave pattern control unit,
The sine wave pattern that maximizes the output of the solar cell by the signal of the maximum power point tracking unit has been stopped until now, and the sine wave pattern with the amplitude value reduced by a predetermined amount is generated. This causes the operating point of the solar cell to temporarily move from near the maximum point to the open-circuit voltage side,
The solar cell operating point voltage exceeds the set value for adjusting the sine wave pattern, the system stop is avoided, and the tracking operation of the maximum power point of the solar cell is started again.

However, if the amount of solar radiation is not sufficient, it will fall below the set value for adjusting the sine wave pattern at the maximum power point of the solar cell, and the sine wave pattern controller again reduces the amplitude value by a predetermined amount. Occur. By repeating this operation, among the sine wave patterns generated from the sine wave pattern control unit, the system operates until the operating point voltage of the solar cell when the sine wave pattern with the smallest amplitude value is input falls below the sine wave pattern set value. Avoid falling below the set value for stop. After that, when the amount of solar radiation further decreases and the PV operating point voltage falls below the set value for system stop smaller than the set value for sine wave pattern adjustment, the system start / stop control unit stops the inverter and shuts off the relay, Stop the supply system.

Even when the system is started up in the morning, even if the amount of solar radiation is not sufficient after the interconnection system is started up, the amplitude of the sine wave pattern is forcibly set to a predetermined amount as when the system is stopped. By using another sine wave pattern with a reduced value, the operating point of the solar cell is temporarily moved from the vicinity of the maximum point to the open circuit voltage side, thereby avoiding falling below the system stop set value.

In this way, it is possible to prevent the system from falling below the set value for system stop when the amount of solar radiation immediately after start-up or immediately before stop is not sufficient, so that stable start-up and stop of the system are possible.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the power supply system start / stop control device of the present invention will be described in detail below with reference to FIG.

FIG. 1 is a diagram showing a grid-connected inverter system including a start-stop control device of the present invention.

Solar cell 1 (output 3.5 kW, open-circuit voltage 2
The output terminal is connected to a backflow prevention diode 6, a DC capacitor 7 that suppresses fluctuations in input power to the inverter 2, and a DC input current detection CT8, and the output terminal of the inverter 2 is connected to the output terminal. An AC output current detecting CT9 is connected. An error amplification signal control circuit 10, a triangular wave signal control circuit 11, which outputs an error signal from the output current signal from the inverter 2 and the sine wave pattern signal output from the sine wave pattern control unit, as a control circuit of the system interconnection system. From the output signal from the error amplification signal control circuit 10 and the output signal from the triangular wave signal generation circuit, P
PWM modulation control circuit 12 for generating a WM modulation signal, PW
There are an inverter drive control circuit 13 that controls an inverter by a signal output from the M modulation control circuit 12, and an interconnection system start / stop control device 14 of the present invention.

Further, the interconnection system start / stop control device 14
Is a DC voltage / current detection unit 15 for detecting the DC voltage and DC current of the solar cell, a DC voltage output from the DC voltage / current detection unit 15, and a maximum power point tracking unit 16 (sampling for determining the maximum power point by the DC current). The time is set to 1/120 second), and the sine wave pattern adjustment unit 17 (the set value for sine wave pattern adjustment is 160) for adjusting the amplitude of the sine wave pattern.
(Set to V), a sine wave pattern control unit 18 (of the sine wave pattern) that generates a sine wave pattern to be input to the error amplification signal control circuit 10 by a signal output from the maximum power point tracking unit 16 or the sine wave pattern adjustment unit 17. The generation method is
A method of storing 200 kinds of sine wave patterns obtained by equally dividing the amplitude of a sine wave having an amplitude of 10 V into 200 steps in ascending order of amplitude and reading out a necessary sine wave pattern is used. If the wave pattern is below the set value, the sine wave pattern used at that time is 5
A system stop control means for simultaneously stopping the inverter 2 and shutting down the interconnection relay 5 with a DC voltage.
While starting the inverter 2, after a set time,
System start / stop control unit 19 (also set to system stop set value 150V and system start set value 170V) that also serves as system start control means for turning on the interconnection relay 5.
Composed of. The DC power output from the solar cell 1 is converted into AC power by the inverter 2 and supplied to the commercial power system 3 and the load 4. An interconnection relay 5 is provided between the inverter 2 and the commercial power system 3 to perform interconnection with and disconnection from the commercial power system.

In this system interconnection system, a sine wave signal is used for P
The inverter 2 is switched by the WM-modulated pulse signal so that a sinusoidal current flows in the output current of the inverter 2, and the output power from the solar cell 1 is supplied to the commercial power system 3 and the load 4. is doing. At this time, the solar cell operating point is tracked near the maximum point on the solar cell output characteristic curve in order to maximize the output of the solar cell 1, but the solar cell operating point is controlled by a PWM pulse signal for switching the inverter 2. Is performed by changing the duty ratio of. Since the duty ratio of the PWM pulse signal is determined by the amplitude of the arbitrary sine wave pattern read by the sine wave pattern control unit 17, the amplitude of the sine wave pattern is controlled to control the solar cell operating point and the inverter 2. It determines the magnitude of the output current.

First, the control operation of the sine wave pattern will be described. First, the sine wave pattern having the smallest amplitude value is read out from the sine wave patterns stored in the sine wave pattern control unit. At this time, the output of the inverter becomes the minimum,
The input voltage and the input current to the inverter of the solar cell at this time are detected by the DC voltage / current detection unit 15, the output power of the solar cell is calculated from the product of them, and the value is once stored in the maximum power point tracking unit. It is stored in the storage unit. Next, read out a sine wave pattern whose amplitude value is one step larger than the previous amplitude value, repeat the same operation to calculate the output power from the solar cell in the maximum power tracking unit, and store it in the maximum power point tracking unit. .

Next, the previous output power value and the current output power value are compared, and if the current output power is larger, the larger current power value is stored instead of the previous power value, and one more step is carried out. A sine wave pattern with a large amplitude value is read out. Then, the output power at this time is detected, and the same processing as the above processing is repeated. On the contrary, if the output power at this time is smaller, a sine wave pattern with an amplitude value one step smaller is read out. Then, the output power value at that time is calculated, and the same processing as the above processing is repeated. In this way, the maximum power point of the solar cell was tracked by selecting a sine wave pattern suitable for the output of the solar cell when the system was started.

Next, the stop operation when the amount of solar radiation decreases in the evening or the like, or the operation of avoiding a malfunction due to a decrease in detection accuracy will be described.

As the amount of solar radiation decreases, the vicinity of the maximum point on the solar cell output characteristic curve becomes gentle, and the detection accuracy of the maximum point decreases. Therefore, the fluctuation range of the operating point of the solar cell that is tracking near the maximum point becomes wide, and the operating point voltage of the solar cell may temporarily fall below the sine wave pattern set value. Further, the voltage of the solar cell itself falls below the sine wave pattern set value. When the operating point voltage of the solar cell falls below the set value for adjusting the sine wave pattern, the signal of the sine wave pattern adjusting unit 17 changes the sine wave pattern that was previously determined by the signal of the maximum power point tracking unit 16. The reading is stopped, and the sine wave pattern in which the sine wave pattern is forcibly reduced by 5 steps in the direction of smaller amplitude is read out.

As a result, the solar cell operating point temporarily moves from the vicinity of the maximum point to the open voltage side, and the solar cell operating point voltage becomes larger than the set value for sine wave pattern adjustment. afterwards,
Starting from the sine wave pattern with the reduced 5-step amplitude value, the maximum operating point of the solar cell is started to be tracked again. However, due to the low solar radiation amount, the solar cell operating point voltage falls below the set value for sine wave pattern adjustment again near the maximum point, but as a result of the processing by the sine wave pattern adjusting unit 17, the solar cell operating point voltage is adjusted to the sine wave pattern adjustment value. Will not exceed the set value for system stop and will not fall below the set value for system stop. After that, while the amount of solar radiation decreases to a certain value, the above phenomenon is repeated, and the operation of the grid interconnection system is stopped without stopping the grid interconnection system, that is, stopping the inverter 2 and disconnecting the interconnection relay 5. It was conducted.

When the amount of solar radiation further decreases and the amplitude of the sine wave pattern cannot be further reduced, the solar cell operating point voltage falls below the system stop set value smaller than the sine wave pattern adjustment set value. The system start / stop control unit 19 stops the inverter 2 and the interconnection relay 5
Was shut down and the grid interconnection system was shut down.
On the other hand, when the amount of solar radiation rises from zero and gradually increases in the morning, etc., when the open-circuit voltage of the solar cell exceeds the system start set value, the system start / stop control unit 19 first starts the inverter 2. To do. And after a set time,
It tries to connect to the commercial power system 3 by turning on the interconnection relay 5, but a voltage drop occurs when the inverter 2 is started. Therefore, the solar cell open voltage is increased before turning on the interconnection relay 5. Is below the set value for system startup, and interconnection relay 5
Is reset and the inverter 2 is restarted from the start. After that, this state is repeated, and when the amount of solar radiation further increases during that time and the increase in the solar cell open-circuit voltage exceeds the voltage drop at the time of starting the inverter 2, following the start of the inverter 2, the interconnection relay 5 Is input, and the grid interconnection system and the commercial power grid 3 are interconnected.

The maximum power point tracking unit 16 starts tracking the maximum point of the solar cell operating point on the solar cell output characteristic curve. However, since the solar radiation is low immediately after startup, the solar cell operating point voltage near the maximum point. May fall below the set value for sine wave pattern adjustment. Also in this case, the solar cell operating point voltage did not fall below the system stop set value by repeating the same operation as the stop operation in the evening or the like. Therefore, it was found that the start-stop control device for the power supply system of the present invention is effective for stable start-up of the power supply system.

[0029]

As described above, by using the power supply system start / stop control device of the present invention, it is possible to prevent the frequent start-up / stop phenomenon at the time of low insolation and the reliability of the device. It is possible to stably start and stop the system interconnection system without adversely affecting.

[Brief description of drawings]

FIG. 1 is a diagram of a grid-connected inverter system that is an embodiment of the present invention.

FIG. 2 is a diagram showing a first example of a conventional system interconnection system start / stop control device.

FIG. 3 is a diagram showing a second example of a conventional system interconnection system start / stop control device.

[Explanation of symbols]

1 Solar Battery 2 Inverter 3 Commercial Power System 4 Load 5 Interconnection Relay 6 Backflow Prevention Diode 7 DC Capacitor 8 DC Input Current Detection CT 9 AC Output Current Detection CT 10 Error Amplification Signal Control Circuit 11 Triangular Wave Signal Control Circuit 12 PWM Modulation Control circuit 13 Inverter drive control circuit 14 System control circuit 15 DC voltage / current detection unit 16 Solar cell maximum power point tracking unit 17 Sine wave pattern adjustment unit 18 Sine wave pattern control unit 19 System start / stop control unit 20 DC side relay

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsukasa Takebayashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (1)

[Claims] 1. A device for controlling starting and stopping of a power supply system for converting direct current power output from a solar cell into alternating current power by a current control type inverter and supplying power to a load. Detection unit for detecting the DC voltage and DC current of the, the maximum power point tracking unit for determining the solar cell maximum power point from the DC voltage and DC current detected by the detection unit, and the reference signal for controlling the inverter When the signal from the sine wave pattern control unit that generates a sine wave pattern, the sine wave pattern adjustment unit that switches the operation of the sine wave pattern control unit, and the detection unit exceeds the system start-up set value, turn on the system. It consists of a system start / stop control unit that starts up and stops the system when it falls below the set value for system stop. When the signal from is detected and the detected signal is below the set value for system stop set value <set value for sine wave pattern adjustment <set value for system startup set value for sine wave pattern adjustment The signal is input to the sine wave pattern control unit, and when it exceeds the set value for sine wave pattern adjustment, the tracking operation signal is input to the sine wave pattern control unit, and the sine wave pattern control unit receives the tracking operation signal. When the adjustment operation signal is received, the sine wave pattern that maximizes the output from the solar cell is output, and when the adjustment operation signal is received, the amplitude is a predetermined amount smaller than the previous sine wave pattern regardless of the maximum power point. A power supply system start / stop control device characterized by outputting a sine wave pattern.