JPH0720956A - Solar battery power source - Google Patents

Abstract

PURPOSE:To speed up transition to a stationary operation state at the start of operation as to the solar battery power source which has a solar battery and a power controller controlling its output electric power. CONSTITUTION:In the solar battery power source 1 which has the solar battery 10 and the power controller 20 controlling the output power of the solar battery 10, the power controller 20 detects an optimum operation point by measuring output characteristics of the solar battery 10 at the start of the operation of the solar battery power source 1 and sets the optimum operation point as a control target to perform power control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell power source having a solar cell and a power control device for controlling its output power.

[0002]

2. Description of the Related Art A solar cell power source having a solar cell and an inverter for converting a direct current output of the solar cell into an alternating current is used in an interconnection system with a commercial power system.

Generally, in this type of solar cell power source, when the sun rises and the amount of solar radiation increases, the inverter is started when the generated power of the solar cell reaches a predetermined value, and power is supplied to the load, that is, the solar cell power source. The operation is started. And during operation, to maximize the power generation capacity of the solar cell,
In the inverter, maximum power point tracking control (MPPT control) that adjusts the output current so that the operating point of the solar cell becomes the optimum operating point (also called the maximum power point) at that time is performed.

In the conventional inverter, immediately after starting, the PWM pulse width that defines the conduction time of the switching element is increased by a predetermined amount. At the same time, the output current and output voltage of the solar cell are detected to output the output power. Then, the PWM pulse width increase / decrease direction is determined to increase the output power based on the change direction of the output voltage of the solar cell and the increase / decrease state of the output power, and thereby the output voltage of the solar cell is made closer to the optimum operating voltage from the open voltage. Was configured as.

[0005]

In order to optimize the operating point of the solar cell, it is necessary to change the output voltage of the solar cell in small steps to find the voltage that maximizes the output power. In addition, due to the control response in the inverter,
It takes about 100 ms, for example, for the operating point to change and stabilize due to the change in the M pulse width, and the PWM pulse width must be changed at least at a time interval longer than that time.

Therefore, conventionally, there has been a problem that it takes a long time of 10 seconds or more from the start of operation to the steady operating state where the operating point of the solar cell is almost the optimum operating point.

Further, in the conventional MPPT control, when an abnormality occurs in the control for some reason, the operation target voltage of the solar cell is assumed to be other than the voltage assumed at the time of design in advance, and the operation condition of the solar cell at that time is changed. There is also a problem that the optimum voltage value cannot be detected.

Further, in the conventional inverter, from the viewpoint of protection for the inverter and the system, only the over- and under-voltages and over-currents on the solar cell side are detected, so that the solar cell array is abnormal (missing module, incorrect wiring, characteristic). There was also a problem that it was not possible to detect (for example, decrease).

In view of the above problems, it is an object of the present invention to speed up the transition to a steady operation state at the start of operation.

[0010]

In order to solve the above problems, a power source according to the invention of claim 1 is a solar cell power source having a solar cell and a power control device for controlling the output power of the solar cell. The power control device detects the optimum operating point by measuring the output characteristics of the solar cell at the start of operation of the solar battery power source, sets the optimum operating point as a control target, and performs power control. Composed.

A power source according to a second aspect of the present invention is a solar cell power source having a solar cell and an inverter, wherein the inverter supplies a capacitor in an uncharged state to the solar cell at the start of operation of the solar cell power source. Connected, the charging current of the capacitor and the terminal voltage are sampled and stored, the optimum operating point of the solar cell is determined based on the sampling data, and the optimum operating point is set as the control target of the input power and the electric power is set. It is configured to do the conversion.

A power supply according to a third aspect of the present invention is configured such that the inverter gradually brings the set value of the control target closer to the optimum operating point.

[0013]

When the operation is started, the output characteristic of the solar cell is measured by, for example, charging the uncharged capacitor with the solar cell. Then, the optimum operating point of the solar cell at that time is detected based on the output characteristics, and power control is performed so that the operating point of the solar cell is set to the optimum operating point.

[0014]

1 is a block diagram showing the overall structure of a solar cell power source 1 according to the present invention. The solar cell power source 1 is composed of a solar cell 10 and a voltage source current control type inverter 20, and is connected to a commercial power system 2. Distribution line 3
A load Z such as various electric appliances is connected to.

The inverter 20 is a reverse blocking 3-terminal thyristor 2 having the functions of a switch and a backflow prevention diode.
1, a smoothing capacitor C0, an inverter main circuit 22, an output filter 23 including a reactor, a relay 24 for canceling the interconnection, a PWM control unit 25 that performs switching control of the inverter main circuit 22, and the entire control of the inverter 20. It is composed of a microcomputer 26 and the like for performing. An operating current is supplied to the PWM control unit 25 and the microcomputer 26 from the solar cell 10 via a constant pressure power supply circuit (not shown).

FIG. 2 is a circuit diagram of the inverter main circuit 22. The inverter main circuit 22 includes four transistors Q1 to Q1 which are switching elements having a self-turn-off function.
4 and four feedback diodes D1 to D4 connected in anti-parallel to each of them.

The inverter main circuit 22 is divided into a set of transistors Q1 and Q4 and a set of transistors Q2 and Q3, and by alternately switching each set, the connection point of the transistors Q1 and Q2 and the transistors Q3 and Q4.
An AC voltage is obtained between the connection point and. By applying pulse width modulation (PWM) to the switching signal, the output voltage waveform can be approximated to a sine waveform, and the output current can be adjusted by setting the pulse width appropriately at that time.

FIG. 3 is a block diagram showing the functional configuration of the PWM control unit 25. The PWM control unit 25 includes a bandpass filter 251, a multiplier 252, an operational amplifier 253, a PWM for extracting the fundamental frequency component of the system voltage Vo.
A feedback control system including a pulse generation unit 254 and a driver circuit 255 for driving the transistors Q1 to Q4, and switching a PWM pulse having a adjusted pulse width to a set of transistors Q1 and Q4 and a set of transistors Q2 and Q3. Inverter main circuit 2 as a signal
Output to 2.

The PWM control section 25 multiplies the signal Sb corresponding to the fundamental frequency component of the system voltage Vo by the input error signal Sa given from the microcomputer 26 to obtain a current command value signal Si indicating a target value for current control. Is generated. Here, the input error signal Sa is the solar cell 10
Is a signal indicating the difference between the input voltage Vi from V and its control target value (voltage command value).

The current command value signal Si is corrected by the actual output current Io and appropriately amplified. Then, in the PWM pulse generator 254, a predetermined PWM pulse is generated by, for example, comparing the current command value signal Si and its phase inversion signal with the modulating triangular wave signal of about 20 kHz, and performing an appropriate logical operation.

By such operation of the PWM control unit 25, in the inverter 20, the value of the input error signal Sa is reduced, that is, the input voltage Vi from the solar cell 10 is the voltage command value set by the microcomputer 26. The output current Io is adjusted so as to match with.

Since the microcomputer 26 generates the input error signal Sa, the input voltage V from the solar cell 10
Based on i and the input current Ii, the input power P that is the power generated by the solar cell 10 is calculated, and the processing for MPPT control that sets the voltage command value so that the input power P is maximized is performed.

In the MPPT control process, PW is determined from the transition direction of the input voltage Vi and the increase / decrease state of the input power P.
The increasing / decreasing direction of the pulse width of the M pulse is determined, the voltage command value is set correspondingly, and the input error signal Sa is generated. When MPPT control is not performed, for example, constant input voltage control is performed. In the constant input voltage control, the voltage at the optimum operating point of the solar cell 10 detected at the start of operation is fixedly set as the voltage command value, and the difference voltage between the voltage command value and the input voltage Vi is fixed. It is obtained as the input error signal Sa.

In the solar cell power source 1 having the above structure,
At the start of operation, the output characteristics of the solar cell 10 are measured, the optimum operating point detected thereby is set as a control target, and power control is started.

FIG. 4 is a flow chart showing the general control contents of the microcomputer 26. In the operation stopped state, the solar cell power source 1 is disconnected from the load Z and the commercial power system 2 while the relay 24 is in the off state. In addition, the four transistors Q1 to Q1 of the inverter main circuit 22
4 and the thyristor 21 are both in the off state, and the capacitor C0 is in the non-charged state with no accumulated charge.

Now, when the sun rises and the open circuit voltage of the solar cell 10 reaches the operating voltage of the microcomputer 26,
An operating current is supplied to the microcomputer 26, and execution of the program starts.

First, the microcomputer 26 waits for the generation of a start request (# 1). The activation request is issued by a solar radiation amount sensor or a voltage monitoring circuit (not shown), for example, when the amount of solar radiation or the open circuit voltage of the solar cell 10 depending on it reaches a predetermined value. Further, it may be issued by a timer circuit at a specific time, or may be issued in response to turning on of an external switch.

When the activation request is generated, the microcomputer 26 turns on the thyristor 21 (# 2).
As a result, as shown in FIG.
Causes the capacitor C0 to be charged. That is, the charging current I flows from the solar cell 10 to the capacitor C0, and the terminal voltage V of the capacitor C0 rises from zero to almost the open circuit voltage Voc of the solar cell 10 within a time of about several milliseconds.
The operating current supplied from the solar cell 10 to the microcomputer 26 is so small that it can be ignored.

While the capacitor C0 is being charged, the microcomputer 26 samples the inter-terminal voltage V and the charging current I at a cycle of, for example, several tens of microseconds, and the sampling data of a plurality of times is sampled in order to reduce the influence of disturbance or the like. An average value is obtained, and the obtained average value data is stored as data indicating the output characteristic (IV characteristic) of the solar cell 10 (# 3).

Then, the electric power value P is obtained by multiplying the voltage V and the current I at each predetermined sampling point (#
4) The maximum electric power Pmax of the solar cell 10 at that time is detected (# 5). Then, the thyristor 21 is once turned off (# 6).

Next, the output characteristic (solid line) and power characteristic (chain line) of the solar cell 10 of which an example is shown in FIG. 6 are checked (# 7). At this time, for example, if at least one of the optimum operating voltage VPmax corresponding to the maximum power Pmax, the open circuit voltage Voc, and the short circuit current Isc has a value outside the predetermined range, it is determined that the characteristic is abnormal. If the output characteristics are abnormal, perform error processing such as displaying a warning (#
8).

On the other hand, when the output characteristic is normal, it is checked whether or not the maximum power Pmax is a certain value or more capable of outputting a predetermined current (# 9). When the maximum power Pmax is smaller than the fixed value, for example, a re-measurement process for measuring the characteristics of the solar cell 10 again is performed after 20 minutes (# 10).

On the other hand, when the maximum electric power Pmax is a certain value or more, the optimum operating voltage VPmax is set as the above-mentioned voltage command value, the input error signal Sa is generated and P
The relay 24 and the thyristor 21 are turned on and the operation of the solar cell power source 1 is started while being sent to the WM control unit 25 (# 11).

However, the solar cell 1 at the start of operation
Since the output voltage 0 (input voltage of the inverter 20) Vi is the open circuit voltage Voc, when the voltage command value is suddenly set to the optimum operating voltage VPmax, there is a possibility that a sudden change in state may adversely affect each part. Therefore, the microcomputer 26 performs so-called soft start processing as
The voltage command value is changed from the open circuit voltage Voc to the optimum operating voltage VPma.
The input error signal Sa is set so as to gradually approach x.
To generate. For example, when the open circuit voltage Voc is 250 volts and the optimum operating voltage VPmax is 200 volts, the voltage command value is lowered by 10 volts at intervals of about 100 milliseconds.

Through the above series of processing, the solar cell power source 1
About 0.5 seconds after the start request is issued, the solar cell 10
In this state, the load Z is fed to the load Z by making the most of its power generation capacity.

In the steady operation state, the microcomputer 26 carries out the steady operation process for generating the input error signal Sa according to the MPPT control or the constant input voltage control (# 12). Since the output characteristics of the solar cell 10 greatly vary depending on the temperature, MPPT control is desirable especially in an environment where the temperature changes greatly. The steady operation process is continued until an operation stop request is issued.

The operation stop request is issued by the solar radiation amount sensor when the amount of solar radiation decreases in the evening, for example. In particular, when constant input voltage control is performed during steady operation, there is a large difference in the amount of solar radiation between the start of operation in the morning and the time of noon, and the output characteristics of the solar cell 10 may also differ. Since the output characteristic is measured again by temporarily stopping the operation, the timer circuit may issue an operation stop request at noon.

When an operation stop request is issued, the microcomputer 26 turns off the relay 24 to release the interconnection (# 14). Subsequently, the thyristor 21 is turned off to disconnect the solar cell 10 from the inverter 20, and a signal S22 for turning on the transistors Q1 to Q4 of the inverter main circuit 22 is sent to the driver circuit 255 of the PWM control unit 25 ( # 15). As a result, the electric charge of the capacitor C0 is discharged through the transistors Q1 and Q2 and the transistors Q3 and Q4.

After the elapse of a predetermined time in which the capacitor C0 is in the non-charged state, the microcomputer 26
All the transistors Q1 to Q4 are turned off, and the process ends (# 16).

According to the above-described embodiment, the output characteristic of the solar cell 10 is first measured instead of adjusting the output current by trial and error in order to increase the output power of the solar cell 10 as in the conventional case. Since the control target is determined and the output current is adjusted, it is possible to quickly shift the solar cell power source 1 to the steady operation state after the operation is started.

According to the above-described embodiment, the characteristic check of the solar cell 10 is performed, and if the result is abnormal, the abnormality process is performed. The operator can know the malfunction of the solar cell 10 such as the disconnection of the module.

According to the above-described embodiment, the commercial power system 2 and the solar cell 10 are connected to the relay 2 when the operation is stopped.
Since it is cut off in triplicate by the inverter 4, the inverter main circuit 22, and the thyristor 21, the DC component does not overlap the commercial power system 2, and the reliability of interconnection protection can be improved.

According to the above-described embodiment, the characteristics of the solar cell 10 are measured at the start of daily operation even when the constant input voltage control is performed in order to simplify the processing during the steady operation. The operation is performed under the optimum conditions regardless of the temperature difference due to the temperature difference, and the power generation capacity of the solar cell 10 can be maximized throughout the year.

In the above embodiment, the type of the solar cell 10 such as the amorphous type or the polycrystalline type is discriminated based on the measurement result of the output characteristics, and the amount of solar radiation and the amount of change in temperature are detected during the steady operation. Thus, the optimum operating point is predicted, and the operating point of the solar cell 10 is shifted from the current point to the predicted optimum operating point at once, so that the MPPT control can be speeded up.

In the above-described embodiment, the function of transferring the measured data of the output characteristic of the solar cell 10 to an external computer or the like, or the function of printing the output characteristic in the form of a graph is provided to facilitate the maintenance of the solar cell power source 1. Can be planned.

In the above embodiment, the commercial power system 2 may be used as the drive power source for the PWM control unit 25 and the microcomputer 26. A transistor may be used instead of the reverse blocking 3-terminal thyristor 21. Further, a soot start may be performed by hardware. In addition, the circuit configuration of the inverter 20, the control mode, the type and configuration of the solar cell 10, and the like can be variously changed in accordance with the gist of the present invention. The present invention can be applied to the solar cell power source 1 that is operated without the interconnection.

[0047]

According to the present invention, it is possible to speed up the transition to a steady operation state at the start of operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a solar cell power source according to the present invention.

FIG. 2 is a circuit diagram of an inverter main circuit.

FIG. 3 is a block diagram showing a functional configuration of a PWM control unit.

FIG. 4 is a flowchart showing an outline of control contents of a microcomputer.

FIG. 5 is a graph showing an example of charging characteristics of a capacitor.

FIG. 6 is a graph showing an example of output characteristics of a solar cell and power characteristics corresponding thereto.

[Explanation of symbols]

 1 Solar Battery Power Supply 10 Solar Battery 20 Inverter (Power Control Device) C0 Capacitor

Claims (3)

[Claims] 1. A solar cell power supply having a solar cell and a power control device for controlling the output power of the solar cell, wherein the power control device has an output characteristic of the solar cell at the start of operation of the solar cell power supply. A solar cell power source, which is configured to measure the optimum operating point, detect the optimum operating point, set the optimum operating point as a control target, and perform power control. 2. A solar cell power source having a solar cell and an inverter, wherein the inverter is:
A capacitor in an uncharged state is connected to the solar cell, the charging current and the terminal voltage of the capacitor are sampled and stored, the optimum operating point of the solar cell is determined based on the sampling data, and the optimum operating point is calculated. A solar battery power source, which is configured to perform power conversion by setting a control target of input power. 3. The solar cell power source according to claim 2, wherein the inverter is configured to gradually bring the set value of the control target closer to the optimum operating point.