JPH06214667A - Output controller for solar battery - Google Patents

Abstract

PURPOSE:To output maximum power from a solar battery even when the amount of insolation and temperature change. CONSTITUTION:The voltage of the solar battery is controlled by an inverter and supplied to a load and the inverter 3 is controlled by a driving device 14. The voltage and the current of the solar battery are detected by detectors 11 and 12 and multiplied by a multiplier 21 and the power is detected. After the elapse of a prescribed time, an output setting device 50 supplies driving control signals for gradually changing an output voltage to the driving device 14. The maximum value of the output of the multiplier 21 is detected by comparators 26 and 36, an AND circuit 30, a clock pulse generator 32, a counter 34 and a D/A converter 28, the output voltage at the time is held in a holding circuit 38 and the driving control signals of the setting device 50 are stopped. Thereafter, an error amplifier 40 supplies the driving control signals to the driving device 14 corresponding to the error of the output of the holding circuit 38 and the detected voltage. After a fixed time, the maximum power is detected and the output voltage at the time is held again similarly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling an output voltage from a solar cell and supplying it to a load, and more particularly to a device which always outputs maximum power from the solar cell.

[0002]

2. Description of the Related Art In a solar cell plate which receives sunlight and generates electric power, an output current Is has a constant value Iop as shown in FIG. 6 when the amount of solar radiation and temperature are constant.
With the increase above, the output voltage Vs drops sharply to zero. The maximum output power P of a solar cell having such characteristics
max occurs when the output current is Iop, and
And the output voltage Vop at this time. A solar cell panel is constructed by attaching 40 to 50 solar cell plates to one panel and connecting them in series or in parallel.

In such a solar cell panel, when the temperature is kept constant and the amount of solar radiation is changed, the relationship between the output current Is and the output voltage Vs is as shown by the solid line in FIG. The curve changes from A1 to A2, and accordingly, the maximum output point also changes from a1 to a2. As a result, the maximum output point changes like the a curve shown by the alternate long and short dash line.

In this solar cell panel, when the temperature is changed while the amount of solar radiation is kept constant, the relationship between the output current Is and the output voltage Vs is as shown by the broken line in FIG. To B2, and the maximum output point also changes from b1 to b2. As a result, the maximum output point changes like the curve b shown by the chain double-dashed line.

Therefore, the maximum output that can be taken out from the solar cell panel in accordance with the change in the amount of solar radiation and the change in temperature moves in the shaded area in FIG.

[0006]

As described above, the maximum electric power that can be extracted from the solar cell changes according to changes in the temperature and the amount of solar radiation, and the maximum electric power cannot be efficiently extracted from the solar cell as it is. There was a problem.

[0007]

In order to solve the above problems, the present invention relates to a solar cell, voltage control means for controlling the output voltage of the solar cell to supply electric power to a load, and the voltage control means. Driving means for driving the control means in response to a drive signal, power detecting means for detecting the output power of the solar cell, voltage detecting means for detecting the output voltage of the solar cell, and the driving for each elapse of a predetermined time Means for supplying the voltage fluctuation signal for gradually changing the output voltage to the means, and continuing the supply of the voltage fluctuation signal until the voltage optimum value detection signal is supplied, and the maximum value of the output power The voltage optimum value detection means for generating the voltage optimum value detection signal at the time of generation, the holding means for holding the output of the voltage detection means in response to the generation of the voltage optimum value detection signal, and the voltage detection means for detecting It said drive control signal corresponding to a difference between the output of the output voltage and the holding means is a control means for supplying to said driving means, in which comprises.

[0008]

According to the present invention, the voltage fluctuation signal is supplied to the driving means by the voltage fluctuation signal supply means every time a predetermined time elapses, and the driving means drives the voltage control means to output the output voltage of the solar cell and Gradually change the output power. These changes in output voltage and power are detected by the voltage detection means and the power detection means. When the output power reaches the maximum power, the voltage optimum value detection means generates a voltage optimum value detection signal. As a result, the voltage fluctuation signal from the voltage fluctuation signal supply means is stopped. At the same time, the holding means holds the output voltage of the solar cell at that time by the voltage optimum value detection signal. The control means supplies a drive control signal to the drive means in accordance with the difference between the voltage detected by the voltage detection means and the voltage held by the holding means. As a result, the electric power extracted from the solar cell becomes the maximum electric power. When a predetermined time elapses, the maximum power is detected again in the same manner as above, the output voltage of the solar cell at that time is held, and voltage control is performed using this as a reference signal. Therefore, even if the temperature or the amount of solar radiation changes during the elapse of the predetermined time, it is possible to cope with the change.

[0009]

EXAMPLE As shown in FIG. 2, this example shows a solar cell 1
This solar cell 1 is connected to a voltage control means, for example, the input side of an inverter 3 via a protection diode 2. This inverter 3 is a transistor or an IG
It is composed of switching elements 4 to 7 such as BT. A load 8 is connected to the output side of the inverter 3 via a reactor 15. The load 8 is connected to a commercial AC power source 10 via a switch 9. This switch 9 is closed when reverse power flow is performed from the solar cell 1 side to the commercial AC power supply 10 side.

The voltage detector 1 is provided between the inputs of the inverter 3.
1 is provided to detect the voltage applied from the solar cell 1 to the inverter 3. Similarly, a current detector 12 is provided in series between the inverter 3 and the solar cell 1 to detect the current supplied from the solar cell 1 to the inverter 3. The detection voltage and the detection current are supplied to the control device 13, and based on the detection voltage and the detection current, the control device 13 supplies a drive control signal to the drive device 14 as described later, and the drive device accordingly. 14 controls each of the switching elements 4 to 7 of the inverter 3 to control the electric power supplied to the load 8 so that the voltage of the solar cell 1 becomes constant.

As shown in FIG. 1, the control device 13 includes a multiplier 21 for multiplying the voltage detected by the voltage detector 11 and the current detected by the current detector 12. Multiplier 2
The multiplication output of 1 represents the output power extracted from the solar cell 1. The multiplier 21, the voltage detector 11, and the current detector 12 constitute power detection means.

The signal representative of this output power is the resistor 22,
The voltage is divided by 23, and the divided signal is supplied to the comparator 26. The output of the D / A converter 28 is supplied to the comparator 26 as a reference signal, and the comparator 26 generates an output "1" while the divided voltage signal is larger than the reference signal. The output signal of the comparator 26 is supplied to the AND circuit 30. While the output of the comparator 26 is "1",
A clock pulse having a constant frequency generated by the clock pulse generator 32 is supplied to the counter 34 via the AND circuit 30. The output of the counter 34 is supplied to the D / A converter 28.

The voltage division signal of the signal representing the power of the solar cell 1 is also supplied to the comparator 36 and further D / A
The output of the converter 36 is also supplied to the comparator 36, which is configured to generate an output "1" when the divided voltage signal becomes smaller than the output of the D / A converter 36. ing. The comparators 26 and 36, the AND circuit 30, the clock pulse generator 32, the counter 34, and the D / A converter 28 constitute voltage optimum value detecting means.

The output of the comparator 36 is supplied to the hold circuit 38, and the voltage signal is also supplied to the hold circuit 38. In the hold circuit 38, the output of the comparator 36 is "1". During the period, the voltage signal immediately before the output of the comparator 36 changes from "0" to "1" is held and output.

The hold output of the hold circuit 38 is
It is supplied to the error amplifier 40. This error amplifier 40
Is also supplied with a voltage-divided signal, which amplifies the error between the two, and the error amplifier 40 supplies it to the drive unit 14 via the diode 42.

Clock pulse generator 32, counter 3
4. The hold circuit 38 includes a clock pulse control circuit 46.
Are reset by a reset pulse signal generated by the. The clock pulse generator 32 is configured to generate a reset pulse signal when an activation signal is input to the activation signal input terminal 48 from the outside, and to generate a reset pulse signal each time a predetermined time elapses. ing.

The reset pulse signal is also supplied to the output setting device 50. The output setting device 50 outputs a drive control signal having a value capable of supplying the minimum voltage Vmin within the maximum current control range from the solar cell 1 to the inverter 3 via the diode 52 when the reset pulse signal is supplied. To the inverter 3 with the passage of time.
It is configured to change the value of the drive control signal so that the voltage supplied to the output voltage increases toward the maximum voltage Vmax. Then, the output setting device 50 includes a comparator 36.
Is also configured to stop the generation of the drive control signal when the output "1" is supplied from.

In this embodiment, when the solar cell 1 is irradiated with sunlight, the solar cell 1 excites a voltage, and this voltage is supplied to the inverter 3 via the diode 2 and the voltage is controlled by the inverter 3. Is supplied to the load 8.

The control of the inverter 3 is performed as follows. When a start signal is input to the start input terminal 48 at time t0 as shown in FIG. 3A, the clock pulse generator 32 generates a reset pulse signal as shown in FIG. 3B. With this reset pulse signal, the clock pulse generator 32, the counter 34, and the hold circuit 3
8 is reset, and the voltage applied to the inverter 3 is gradually increased from the minimum voltage Vmin to the maximum voltage Vmax, so that the output setting device 50 changes the value of the drive control signal as shown in FIG. Change gradually.

When the voltage is thus changed from Vmin to Vmax, the electric power P that can be taken out from the solar cell 1 gradually increases as shown in FIG. 4, and the maximum electric power Pma is obtained.
x and then decrease.

In order to detect the state in which the maximum power Pmax is obtained, the detection output of the voltage detector 11 and the detection output of the current detector 12 are multiplied by the multiplier 21, and the result shown in FIG.
A signal representing power is generated as shown in (e). This signal is divided by the resistors 22 and 23 and the comparator 26
, Where it is compared with the output from the D / A converter 28.

However, since the counter 34 supplying the signal to the D / A converter 28 is initially reset and the output is 0, the output of the D / A converter 28 is also 0, and the divided voltage signal is obtained. Is larger than the output of the D / A converter 28, the output of the comparator 26 is “1” as shown in FIG.
Becomes

Since this output "1" is supplied to the AND circuit 30, as shown in FIG.
The clock pulse of the clock pulse generator 32 is supplied to the counter 34 via the, and is counted here, the count value is increased, and this is analog-converted by the D / A converter 28 and supplied to the comparator 26. Therefore, the comparator 26
The reference signal being supplied to the solar cell 1 increases as the voltage from the solar cell 1 increases from Vmin.

When the electric power detected by the multiplier 21 reaches the maximum electric power Pmax and then becomes slightly smaller than Pmax at time t1, the divided voltage signal supplied to the comparator 26 is the D / A converter. Since it is smaller than the output of 28 (corresponding to the maximum power), the output of the comparator 26 becomes "0" as shown in FIG. 3 (f). As a result, the supply of the clock pulse to the counter 34 via the AND circuit 30 is stopped as shown in FIG.

On the other hand, the comparator 36 also receives the divided voltage signal and D / A.
Since the output signal of the converter 28 is supplied, the time t
At 1, the comparator 36 supplies the output "1" to the hold circuit 38 as shown in FIG. by this,
The hold circuit 38 holds the voltage signal generated immediately before the output becomes “1” (voltage signal when the maximum power Pmax is generated). The output of the comparator 36 is "1".
Is supplied to the output setting device 50, and the output setting device 50 stops the supply of the drive control signal as shown in FIG.

After that, the difference between the hold signal (the voltage signal when the maximum power Pmax is generated) held in the hold circuit 38 and the voltage signal is amplified by the error amplifier 40 and passed through the diode 42 as a drive control signal. Is supplied to the driving device 14. After that, feedback control is performed so that the maximum power Pmax is extracted from the solar cell 1.

At a time t2 when a predetermined time T2 has elapsed from the time t0, the clock pulse control circuit 46 outputs the reset pulse to the clock pulse generator 32, the counter 34, the hold circuit 38, and the output setting as described above. Supply to the device 50. After that, in the same manner as described above, the maximum power is detected, the output voltage when the maximum power is generated is held, and the control is performed based on this held voltage.

Therefore, if the time T1 from the time t0 to the time t1 is selected to be sufficiently shorter (for example, 1/10) than the period (T2-T1) in which the maximum electric power Pmax is constantly output, it is selected. , The period from time t1 to t2,
Maximum power can be extracted. Further, if the period T2 from the generation of the reset pulse to the generation of the reset pulse is set to be relatively short (for example, 1 minute), the maximum power after the change can be taken out even if the amount of solar radiation or the temperature changes. .

In the above embodiment, two comparators 26, 3 are provided.
6, the comparator 36 is removed, and the comparator 26 is used.
May be inverted by an inverter and supplied to the hold circuit 38 and the output setting device 50.

Further, although the above-mentioned embodiment is centered on analog control, it may be carried out by digital control using a microcomputer or the like. In this case,
The solar cell 1, the protection diode 2, the inverter 3, the voltage detector 11, and the current detector 12 are used in the same manner as in the case of 1., and the outputs of the voltage detector 11 and the current detector 12 are digitized and supplied to the microcomputer. , The output of the microcomputer is converted into an analog signal by the D / A converter and is supplied to the switching elements 4 to 7 of the inverter 3.

A flow chart in this case is shown in FIG.
First, the output voltage and output current of the solar cell 1 are detected (step S2), and the output power is calculated (step S4).
It is determined whether this power is the maximum value (step S6).
If it is not the maximum value, the voltage supplied to the inverter 3 is Vm.
The control value is changed so as to slightly change from in to the Vmax side (step S8), the inverter 3 is controlled according to this control value (step S10), and the process returns to step S2,
Until the power reaches the maximum value, steps S2, 4, 6, 8,
Execute 10 loops.

When the maximum power is eventually detected (Yes in step S6), the control value at that time, that is, the optimum output voltage value is stored (step S12), and the output power of this solar cell 1 becomes the maximum power. That is, the constant voltage control is performed on the inverter 3 so as to correspond to the control value stored in step S12 (step S18). Then, it is determined whether a predetermined time has elapsed (step S2
0) If it has not elapsed (No in step S20), the process returns to step S18, the loop of steps S18 and S20 is executed, and the constant voltage control is continued. Step S2
When the determination of 0 is YES, that is, when the predetermined time has elapsed, the process returns to step S2 and the control value is reset again.

[0033]

As described above, according to the present invention, the optimum output voltage value for generating the maximum power to be taken out from the solar cell is detected and held, and the held optimum output voltage value is used as the reference signal to determine the predetermined value. The voltage control means is controlled for a time, and after the predetermined time has elapsed, the optimum output voltage value is detected and held again, and the voltage control is performed for the predetermined time by using the held optimum output voltage value as a reference signal. Since the control of the means is repeated, the maximum electric power can always be taken out from the solar cell even if the amount of solar radiation or the temperature changes.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a first embodiment of a solar cell output control device according to the present invention.

FIG. 2 is an overall block diagram of the first embodiment.

FIG. 3 is a timing chart for explaining the operation of the first embodiment.

FIG. 4 is a diagram showing a relationship between output current and electric power of the solar cell used in the first embodiment.

FIG. 5 is a flowchart of the second embodiment.

FIG. 6 is a diagram showing a relationship between an output current and an output voltage of a solar cell.

FIG. 7 is a diagram showing a state in which the relationship between the output current and the output voltage of the solar cell changes according to changes in the amount of solar radiation and temperature.

FIG. 8 is a diagram showing a state in which the maximum electric power in the solar cell changes according to changes in the amount of solar radiation and temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 solar cell 3 inverter (voltage control means) 8 load 11 voltage detector (power detection means) 12 current detector (power detection means) 14 driving device (driving means) 21 multiplier (power detection means) 26 comparator (voltage Optimal value detection means 28 D / A converter (voltage optimum value detection means) 30 AND circuit (voltage optimum value detection means) 32 Clock pulse generator (voltage optimum value detection means) 34 Counter (voltage optimum value detection means) 36 Comparator (voltage optimum value detection means) 38 Hold circuit (holding means) 40 Error amplifier (control means) 50 Output setting device (voltage fluctuation signal supply means)

Claims (1)

[Claims] 1. A solar cell, voltage control means for controlling an output voltage of the solar cell to supply electric power to a load, driving means for driving the voltage control means according to a drive signal, and the solar cell An electric power detection unit that detects output electric power, a voltage detection unit that detects the output voltage of the solar cell, and a voltage fluctuation signal that gradually changes the output voltage to the driving unit each time a predetermined time elapses. Voltage fluctuation signal supply means for continuing to supply the voltage fluctuation signal until the voltage optimum value detection signal is supplied, and voltage optimum value detection means for generating the voltage optimum value detection signal when the maximum value of the output power is generated, Holding means for holding the output of the voltage detecting means in response to the generation of the voltage optimum value detection signal, and a difference between the output voltage detected by the voltage detecting means and the output of the holding means. An output control device for a solar cell, comprising: a control unit that supplies the drive control signal to the drive unit.