JPH08149833A - Controlling power circuit and protective circuit for solar battery generator - Google Patents

Abstract

PURPOSE: To provide a solar battery generator capable of starting an inverter quickly in a stabilized state. CONSTITUTION: The title controlling power circuit has a power source board 10 for converting the output voltage of a solar battery 1 into a controlling power voltage and supplying it to an inverter control circuit 8, and the control circuit 8 is fitted with an A/D converter 12 which operates using the controlling power voltage as a reference voltage. Besides, the control circuit 8 is provided with a correcting reference voltage generating part 16 which generates a correcting reference voltage of a constant level, and supplies it to the input terminal of the A/D converter 12, and a data processing part 13 which generates a correction data for correcting an A/D conversion error on the basis of the digital data of the correcting reference voltage to be outputted from the A/D converter 12, and corrects the digital data of the output signal of an inverter main circuit 2 by this correcting data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control power supply circuit and a protection circuit for a solar cell power generator that converts direct current power supplied from a solar cell into alternating current and outputs the alternating current.

[0002]

2. Description of the Related Art In recent years, a new direct current energy source represented by a solar cell is installed in each home, factory or area, and is connected to a commercial power grid of an electric power company. A power system that flows backward to the grid has been put to practical use.

In a conventional power system using a solar cell, DC power supplied from the solar cell is converted into AC power by an inverter and output to a commercial power system. The inverter includes an inverter main circuit including a switching circuit, a drive circuit that drives the main circuit, and an inverter control circuit that supplies a drive signal to the drive circuit. The inverter control circuit is provided for obtaining maximum power. An operation control unit that creates a current control signal and a protection function processing unit that performs a protection operation such as disconnecting the inverter main circuit from the commercial power system when an abnormality occurs in the operation state of the inverter are provided.

Also, for operation control and protection operation, the output current and output voltage of the inverter main circuit are detected, and these analog detection values are converted into digital detection values by the A / D converter built in the control circuit. It is converted and supplied to the operation control unit and the protection function processing unit. Here, as a control power source of the inverter control circuit, there are a DC power source system in which the output terminal of the solar cell, that is, the DC side, and an AC power source system in which the output terminal of the inverter main circuit, that is, the AC side is used. In the direct current method, the power supply is stopped at night, but in the solar cell power generator, the function of the control circuit can be stopped at night. Therefore, the direct current power supply method is advantageous in terms of power saving and the like.

When the DC power supply system is adopted, the output voltage (for example, 200V) of the solar cell is the control power supply voltage (for example, 5V).
V) and is supplied to the control circuit, but at night, the output voltage of the solar cell drops to almost zero, and the control circuit is substantially in the sleep mode in which the function is stopped. After that, when the solar cell starts to be exposed to sunlight at dawn, the output of the solar cell gradually rises, and when the control power supply voltage exceeds a certain value (for example, 4.5 V), the control circuit goes out of sleep mode. Escape and start working. However, the control power supply voltage at this time has not reached the reference voltage (for example, 5 V) that guarantees normal operation of the control circuit, so various inverter start conditions are checked to prepare for inverter start (standby. mode). Then, when the amount of solar radiation further increases, the control power supply voltage reaches the reference voltage, and the inverter start condition is satisfied, the inverter main circuit is started.

[0006]

However, in the conventional solar battery power generator, the period until the control power supply voltage reaches the reference voltage after the control circuit exits the sleep mode and starts the operation is the reference voltage. Since a low voltage that does not reach the voltage is supplied to the reference voltage input terminal of the A / D converter in the control circuit, an error occurs in the A / D conversion operation.

For example, the rated value of the output voltage of the solar cell is set to 2
00V, which is converted to 1/40 of 5V and used as a control power supply, and the A / D converter uses 5V as a reference voltage.
Shall be supplied. Further, when a reference voltage of 5V is input to one input terminal of the A / D converter, the A / D converter converts it into digital data of 200V and outputs it. That is, the A / D converter performs 5: 200 conversion with 5V as the full scale.

As an input signal to the A / D converter, 2.5
If V is input, the A / D converter outputs the digital data X of the following expression 2 from the proportional relationship of the following expression 1.

[Equation 1] 5: 200 = 2.5: X

[Formula 2] X = 200 × 2.5 / 5 = 100 (V)

On the other hand, assuming that the reference voltage is 4.5 V immediately after the control circuit starts operating after exiting from the sleep mode, when 2.5 V is input to the A / D converter, A The / D converter outputs the digital data of the following expression 4 from the proportional relationship of the following expression 3 with a full scale of 4.5V.

[Formula 3] 4.5: 200 = 2.5: X ′

## EQU4 ## X '= 200 × 2.5 / 4.5 = 111.1 (V)

That is, for A / D conversion of the A / D converter 11.
An error of 1V will occur. Such an error causes a misjudgment when the control circuit checks the inverter starting condition, and in some cases causes the protection circuit to malfunction. If the protection circuit malfunctions when the inverter starts,
After that, the standby mode is maintained until it is recognized that the inverter start condition is satisfied.

When the power supply to the inverter control circuit is turned on or the reset operation is performed, the microcomputer forming the control circuit first performs an initial operation such as a memory clear. The output state of the computer becomes unstable. Therefore,
In the process in which the control circuit checks the inverter starting condition, there is a possibility that a misjudgment may occur due to the instability of the output state, and the protection circuit will also malfunction.

Even if the protection circuit malfunctions and the inverter starts up, if the operation of the microcomputer is unstable, the operating state becomes abnormal, and immediately after that, the protection circuit operates and the inverter operates. Will stop.

As described above, in the conventional solar cell power generator, the protection circuit sometimes malfunctions when the inverter starts up, which results in a problem that it takes time for the inverter to start normally. It is an object of the present invention to provide a solar cell power generation device that eliminates the above-mentioned problems at the time of startup and can quickly start up an inverter.

[0014]

A control power supply circuit for a solar cell power generator according to the present invention creates a reference voltage for correction at a constant level and outputs it to one input terminal of an A / D converter (12). A correction for correcting the A / D conversion error due to the shortage of the reference voltage, based on the supplied correction reference voltage creating means and the digital data of the correction reference voltage output from the A / D converter (12). Data processing means for creating data and correcting digital data of the output signal of the inverter main circuit (2) by the correction data.

The protection circuit of the solar cell power generator according to the present invention is provided with a protection function processing means for causing the disconnection operation of the disconnection device when an abnormal operating state occurs, and the control circuit.
For (8), a disabling means is provided for disabling the operation of the protection function processing means for a certain period of time after power-on or reset.

Another protection circuit of the solar cell power generator according to the present invention supplies the control circuit (8) to the inverter main circuit (2) for a certain period of time after power-on or reset of the control circuit (8). A nullifying means for nullifying the control signal for driving is provided.

[0017]

In the control power supply circuit of the present invention, the A / D
When the voltage of the control power supply supplied to the converter (12) is lower than a predetermined reference voltage, digital data of the output signal of the inverter main circuit (2) obtained from the A / D converter (12) At the same time that the A / D conversion error occurs due to the shortage of the reference voltage, the digital data of the correction reference voltage also causes the A / D conversion error due to the shortage of the reference voltage at the same rate. Here, since the correction reference voltage supplied to the A / D converter (12) has a known value at a constant level, the ratio of the error generated in the digital data after the A / D conversion of the correction reference voltage is calculated. It can be calculated.

Therefore, it is possible to create correction data for correcting the A / D conversion error based on the digital data of the correction reference voltage. Correcting the digital data of the output signal of the inverter main circuit (2) with the correction data makes it possible to obtain accurate digital data obtained when the reference voltage has a specified value, and to supply the digital data to the protection circuit. Therefore, the protection circuit does not malfunction.

In the above protection circuit of the present invention, when the control circuit (8) is powered on or reset, the output state of the microcomputer constituting the control circuit (8) is kept for a short period immediately after that. Although it becomes unstable, during this period, the operation of the protection function processing means constituted by the microcomputer is invalidated, so even if an erroneous judgment occurs in the protection function processing means, the inverter main circuit ( 2) will not be disconnected from the commercial power system (3).

In the other protection circuit of the present invention, when the control circuit (8) is turned on or reset, the control circuit (8) outputs the inverter main circuit (for a short period immediately after that). Since the control signal for driving to 2) is invalidated, the inverter main circuit (2) does not start while the operation of the microcomputer constituting the control circuit (8) is unstable. Therefore, normal startup can always be performed.

[0021]

According to the solar cell power generator of the present invention, the inverter can be quickly started in a normal state.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Two embodiments of the present invention will be specifically described below with reference to the drawings. First Embodiment As shown in FIG. 1, the solar cell (1) includes an inverter main circuit (2).
Is connected to the commercial power system (3) via a relay (4) between the inverter main circuit (2) and the commercial power system (3).
And the breaker (5) is interposed. Inverter main circuit
(2) is driven by the switching pulse supplied from the drive circuit (9), and the drive circuit (9) is a control circuit
It is controlled by the drive signal from (8).

The alternating current and voltage (system voltage) output from the inverter main circuit (2) are respectively detected by CT (6) and PT (7) provided at the output end of the inverter main circuit (2). , Current detection signal Iac and voltage detection signal Vac
Is input to the one-chip microcomputer (11) that constitutes the control circuit (8). Microcomputer (11)
Is a multi-channel A / D converter (12) for converting the detection signals Iac and Vac output from the inverter into digital data.
And a data processing unit (13) that should perform a predetermined data process described below on the converted data by the A / D converter (12), and executes a protection function operation based on the data from the data processing unit (13). It has a protection function processing unit (14). Current control signal I generated by the microcomputer (11)
The value o is supplied to the current controller (15) to generate a drive signal for the drive circuit (9).

At the output end of the solar cell (1), the solar cell (1)
A power supply board (10) which should convert the direct current 200V obtained from the power supply board to a control power supply voltage of 5V is connected, and the control power supply obtained from the power supply board (10) is supplied to the control circuit (8). A / in the A / D converter (12) of (11)
It is used as a D conversion reference voltage and also as a power source for a correction reference voltage creating unit (16) described later.

The protection function processing unit (14) of the microcomputer (11) sends a gate block signal to the current control unit (15) when it detects an abnormal operation state by executing a predetermined protection function operation. , Gates the drive signal output from the current control unit (15) to stop the operation of the inverter main circuit (2). In addition, the protection function processing unit (14) is a relay
Create a relay ON / OFF signal to open (4) and send it to the relay (4).
Create a breaker trip signal and send it to the breaker (5).

Correcting reference voltage generating section (16) of the control circuit (8)
Is supplied with control power from the power board (10) and creates a reference voltage for correction at a constant level (for example, 1.2 V).
The signal is supplied to the input terminal of one channel of the / D converter (12). As the correction reference voltage generating unit (16), for example, a commercially available IC package that has been subjected to temperature compensation can be used, and even when the voltage of the control power supply drops to 5 V or less, the correction reference voltage remains unchanged. It is kept constant.

FIG. 2 shows an A / D converter (12) and a data processing section.
(13) and the protection function processing unit (14) represent the procedure to be executed. The A / D converter (12) converts the output current Iac and the output voltage Vac of the inverter main circuit (2) into digital data, and the correction reference voltage (1. 2V) is converted into 10-bit digital data, and these converted data are supplied to the data processing unit (13) (step S1). The data processing unit (13) converts the 10-bit conversion data into the original voltage signal (step S2).

Here, the A / D converter (12) has a reference voltage.
A / D conversion is performed by making (normally 5V) correspond to a 10-bit full scale, whereby a 5V analog signal is associated with 200V digital data. For example, when the winding ratio of PT (7) is 1/40, the output voltage 10
0V is converted to 2.5V, and is input to one channel of the A / D converter (12) as the voltage detection signal Vac. In this case, the voltage value X1 converted and output by the data processing unit (13) is obtained from the following equation 6 from the proportional relation of the following equation 5.

[Formula 5] 5: 200 = 2.5: X1

[Equation 6] X1 = 200 × 2.5 / 5 = 100 (V)

With respect to the correction reference voltage (1.2 V) from the correction reference voltage generation unit (16), the voltage value X2 converted and output by the data processing unit (13) is expressed by the following formula 7. From the proportional relationship of

[Formula 7] 5: 200 = 1.2: X2

[Expression 8] X2 = 200 × 1.2 / 5 = 48 (V)

However, the output voltage of the solar cell (1) does not reach 200V immediately after the control circuit (8) exits from the sleep mode or in a time zone when the amount of solar radiation is insufficient. When the A / D conversion reference voltage applied is as low as 4.5 V, the A / D converter (12) converts the reference voltage of 4.5 V into 10 / bit full scale.
D conversion is performed so that a 4.5V analog signal is associated with 200V digital data. Therefore, the voltage detection signal Vac of 2.5V is output to the A / D converter (12).
The voltage value X1 ′ converted and output by the data processing unit (13) when input to the above is obtained from the following equation 10 from the proportional relation of the following equation 9.

## EQU9 ## 4.5: 200 = 2.5: X1 '

## EQU10 ## X1 '= 200 × 2.5 / 4.5 = 111.1 (V)

In this way, an A / D conversion error of about 11.1% occurs with respect to the correct converted value of 100V. If the reference value of the protection operation by the protection function processing unit (14) is 110V, the inverter will be in the standby mode although the actual output voltage is 100V and normal.

As for the correction reference voltage (1.2 V) from the correction reference voltage creating section (16), the voltage value X2 'converted and output by the data processing section (13) is as follows. From the proportional relationship of 11, it is obtained as shown in the following Expression 12.

[Expression 11] 4.5: 200 = 1.2: X2 ′

## EQU12 ## X2 '= 200 × 1.2 / 4.5 = 53.3 (V) Thus, an A / D conversion error of about 11.1% occurs with respect to the correct converted value of 48V.

Here, the error rate (11.1%) contained in the voltage value X2 'after A / D conversion of the correction reference voltage and the voltage value X1' after A / D conversion of the voltage detection signal Vac. The error rate (11.1%) included in the above should have the same value because the cause of the error is the same. In other words, the ratio of the correction reference voltage to the normal value of the A / D converted voltage value X2 ′ and the A / D converted voltage value X of the voltage detection signal Vac.
The ratio of 1'to the normal value is the same value as expressed by the following equation 13.

X2 '/ X2 = X1' / X1

Therefore, the correct conversion value X1 of the voltage detection signal Vac can be calculated by the following equation (14).

X1 = X1 ′ (X2 / X2 ′) For example, in the case of the above calculation example, X2 = 48, X2 ′ = 5
Substituting 3.3 into the equation (14), the correction equation of the following equation (15) is obtained.

[Formula 15] X1 = 0.9 · X1 ′

Then, by substituting X1 ′ = 111.1, X1≈100.0 V is obtained. In this way, by using the above correction formula, accurate conversion data can be obtained, and if the conversion data is supplied to the protection function processing unit (14), no malfunction occurs.

Therefore, the data processing unit (13), in step S4 of FIG. 2, detects the inverter output detection signals Iac and Va.
For the digital data of c, the above equation 15 for each data
Corrected using the correction formula of, and the result is correct A / D
Use the converted value of conversion.

However, the data processing unit (13) does step S3.
First, it is judged whether the conversion result X2 'of the correction reference voltage is within an error range of ± 5% with respect to the normal value X2. If it is within the error range, go to step S5. After that, the correction in step S4 is omitted. This is ± 5
This is based on the judgment that if it is within the error range of%, it does not cause the malfunction of the protection function processing unit (14).

Next, in step S5, the protection function processing unit (1
As one of the protection operations of 4), it is determined whether the converted value of the A / D conversion of the AC voltage is higher than the protection reference level of 110 V. If YES, the gate block signal is changed in step S6. The current is sent to the current control unit (15) to stop the inverter circuit, and at the same time, the relay (4) is opened to put the inverter in the standby mode. If the determination in step S5 is no, the process proceeds to step S7, and detection and protection processing of other protection items is executed.

According to the control power supply circuit of the solar cell generator, the control power supply voltage does not reach the reference value immediately after the microcomputer (11) of the control circuit (8) exits from the sleep mode, and the A / D Even if an error occurs in the A / D conversion by the converter (12), the error is corrected in the data processing unit (13) and the protection function processing unit (14) performs a correct protection operation.

Second Embodiment In the solar cell power generator shown in FIG. 3, the current controller (1
The drive signal sent from 5) is supplied to the drive circuit (9) via the gate circuit (17). Microcomputer
Relay ON / OFF signal and breaker trip signal output from (11) are relayed through NAND gates (21) and (22).
It is supplied to (4) and the breaker (5).

Further, a reset circuit (23) having a reset button (18) for resetting the microcomputer (11) is provided. In the circuit, the reset button (18)
It is connected to the reset terminal of the microcomputer (11) via the first flip-flop (19) and is connected to the gate circuit (17) and the NAND gates (21) and (22) via the second flip-flop (20). ing. Further, the voltage Vcc is input from the control power supply to the first flip-flop (19) and the second flip-flop (20).

The first flip-flop (19) has a reset button (1
In response to the operation signal from 8), a reset pulse that goes low for a period of 1 ms is generated to reset the microcomputer (11). The second flip-flop (20) has a reset button
In response to the operation signal from (18), a mask pulse (gate block) that becomes high is generated for a period of 20 ms to mask the drive signal to the drive circuit (9) and to the NAND gates (21) and (22). The relay ON / OFF signal and the breaker trip signal are masked.

FIG. 4 shows the first flip-flop (19) and the second flip-flop (20) when the reset button (18) is operated.
Represents the binary state of each output terminal. Reset button (1
Immediately after the operation signal from 8) changes from low to high, 1 ms
At the time when has passed, the reset pulse to the reset terminal of the microcomputer (11) becomes high, and the microcomputer (11) is reset. Then the reset button
During the period from the operation of (18) until 20 ms elapses, the mask pulse to the gate circuit (17) and the NAND gates (21) and (22) becomes high, and the drive signal is sent to the drive circuit (9). While the gate block is applied, the relay ON / OFF signal and the breaker trip signal to the NAND gates (21) and (22) are masked.

After the lapse of the 20 ms period, the mask pulse becomes low, the gate block of the drive signal to the drive circuit (9) is released, and the protection operation by the microcomputer (11) is enabled. . Therefore, there is no possibility that the relay (4) or the breaker (5) will malfunction due to an unstable state immediately after the microcomputer (11) is reset.

FIG. 5 shows the power supply monitoring function of the reset circuit (23). Control power supply voltage V as shown
When cc drops from the normal value of 5V and then returns to 5V and exceeds 4.5V, the microcomputer (11) exits the sleep mode and starts operating. In this case, similar to the operation of the reset button (18) described above,
The output terminal of the first flip-flop (19) is low for a period of 1 ms, and the output terminal of the second flip-flop (20) is 20 ms.
During the period, the microcomputer (11) is prevented from malfunctioning due to insufficient power supply voltage.

According to the protection circuit of the solar cell device described above, the unstable output state when the microcomputer (11) is turned on or the reset operation is masked, the inverter main circuit (2 ) Does not start in an unstable control state, and the relay (4) and breaker (5) may malfunction.

The above description of the embodiments is for explaining the present invention and should not be construed as limiting the invention described in the claims or reducing the scope. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a solar cell power generation device according to the present invention.

FIG. 2 is a flowchart showing the operation of the first embodiment.

FIG. 3 is a block diagram showing a configuration of a second exemplary embodiment.

FIG. 4 is a time chart explaining an operation associated with operation of a reset button in the second embodiment.

FIG. 5 is a time chart for explaining the operation accompanying the restoration of the control power supply voltage in the second embodiment.

[Explanation of symbols]

 (1) Solar cell (2) Inverter main circuit (3) Commercial power system (4) Relay (5) Breaker (8) Control circuit (11) Microcomputer (12) A / D converter (16) Correction reference voltage Creation department

Front page continuation (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H02J 3/38 R 9470-5G (72) Inventor Masahiro Maekawa 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. An inverter main circuit (2) for converting DC power supplied from a solar cell (1) into AC and outputting the AC power, a control circuit (8) for controlling the inverter main circuit (2), and a solar Control circuit that converts the output voltage of the battery (1) into the power supply voltage for control
The control circuit (8) is equipped with an A / D converter (12) that operates using the control power supply voltage from the voltage conversion circuit as a reference voltage. In a solar cell power generator in which the output signal of the inverter main circuit (2) is input to at least one input terminal of the / D converter (12) and which is used for control operation or protection operation by the control circuit (8). , Create a constant level correction reference voltage, and
Based on the correction reference voltage creating means to be supplied to the other one input terminal of (12) and the digital data of the correction reference voltage output from the A / D converter (12), A /
Solar cell power generation, comprising: correction data for correcting D conversion error, and data processing means for correcting digital data of an output signal of the inverter main circuit (2) by the correction data. Power supply circuit for device control. 2. An inverter main circuit (2) which converts direct current power supplied from a solar cell (1) into alternating current and outputs the alternating current, is connected to a commercial power system (3) through a paralleling device, The inverter main circuit (2) is a solar cell power generator controlled by the control circuit (8), and is provided with a protection function processing means for causing the disconnecting operation to be disconnected when an abnormal operating state occurs, and the control circuit A protection circuit for a solar battery power generation device, characterized in that it is provided with invalidation means for invalidating the operation of the protection function processing means for a certain time after the power is turned on or reset for (8). 3. An inverter main circuit (2) which converts direct current power supplied from a solar cell (1) into alternating current and outputs it is connected to a commercial power system (3), and the inverter main circuit (2) is In the solar cell power generator controlled by the control circuit (8), a control for driving that is supplied from the control circuit (8) to the inverter main circuit (2) for a certain period of time after power-on or reset of the control circuit (8). A protection circuit for a solar battery power generation device, which is provided with a nullifying means for nullifying a signal.