JPH0827671B2 - Solar cell output power regulator - Google Patents

Description

Description: TECHNICAL FIELD The present invention generally relates to an output power adjustment device for a solar cell, and more specifically, it includes an inverter or a power converter such as a power supply for supplying power to an AC or DC load. The present invention relates to a solar cell output power adjusting device.

[Conventional technology]

As is well known, the output of a solar cell changes significantly depending on the amount of solar radiation and the operating point voltage or current. Therefore, it is required to adjust the load seen from the solar cell and always extract the maximum electric power. .

However, even if the solar radiation changes, the voltage that generates the maximum output at that time does not change much, so the load amount is adjusted so that the solar cell voltage becomes the voltage value (constant value) that generates the maximum output. Just do it. FIG. 5 (a) is a block diagram showing an example of the configuration of a conventional solar cell output power adjusting apparatus. The outline of the adjusting device is as follows. That is, solar cell 1 to constant frequency inverter 2, transformer 3
The voltage of the solar cell 1 is detected by the voltage detecting means 6 when the electric power is supplied to the other electric power system 4 via the, and the deviation between the detected voltage signal and the operating point voltage set value by the voltage setter 7 is added. After being obtained by the voltage regulator 8, the voltage control circuit 9 outputs the phase difference command signal δ between the voltage signal in the constant frequency inverter 2 and the voltage signal in the system 4. Phase control circuit 10
Is a voltage / frequency converter so that the phase difference between the output voltage signal of the constant frequency inverter 2 detected by the phase difference detection circuit 11 and the voltage signal in the system 4 becomes equal to the command value δ.
12 outputs, ie oscillation frequency (phase) of constant frequency inverter 2
To adjust. In this case, since the passing power of the constant frequency inverter 2 is adjusted according to the phase difference between the output voltage signal of the constant frequency inverter 2 and the voltage signal of the grid 4, the voltage of the solar cell is eventually the voltage setting device 7. It will operate with the optimum value set in. Reference numeral 13 is a diode connected to prevent backflow from the constant frequency inverter 2 side. FIG. 5 (b) is a block diagram showing another example of the configuration of the conventional output power adjusting device for a solar cell. The outline of the adjusting device is as follows. That is, the solar cell 1 is used as a power source, and the pump 15 is driven by the AC motor 14 via the variable voltage variable frequency inverter 2a using pulse width modulation (PWM).
The voltage detecting means 6 detects the voltage of the solar cell 1 when driving, and the variable voltage variable frequency inverter via the voltage control circuit 9 so that the voltage is equal to a predetermined set value given by the voltage setter 7. Controlling the frequency of 2a was done. That is, in the control as described above, the load amount of the inverter 2a is adjusted by changing the rotation speed of the electric motor 14 so that the operating voltage of the solar cell 1 becomes a predetermined value even if the solar radiation fluctuates. By making such adjustments, the maximum output power could always be obtained from the solar cell 1. In this case, the output voltage from the inverter 2a is set by the output voltage setting device 16 of the inverter 2a so as to be proportional to the frequency, whereby the pulse width for operating each switch provided in the inverter 2a. Is controlled (see Japanese Patent Application Laid-Open No. 56-132174).

[Problems to be solved by the invention]

By the way, as shown in FIG. 6, if the temperature of the solar cell 1 changes, the maximum output point voltage (vop) also changes considerably, and in the above-mentioned conventional output power adjusting device, when the operating point shifts, the output Rapidly decreases, the temperature (T
It was necessary to change the voltage setting value according to j). In addition, care must be taken in selecting the set value such that the above-mentioned optimum voltage is different for each solar cell used.

Therefore, in view of such a point, a method called a so-called mountain riding method was devised as a method for automatically finding the maximum power point and operating at that point regardless of the change in the characteristics of the solar cell. In this method, the output of the solar cell measured at a certain operating point is stored, and then the load is changed by increasing or decreasing the frequency to shift the operating point of the solar cell. Even if the output is measured and compared with the previous sample value, if the output is increased, it is determined that the direction of the frequency change is correct, and then the frequency is changed in the same direction. On the other hand, if the output difference of the solar cell decreases, the direction of the change in the frequency is changed in the opposite direction due to an error, and it is possible to automatically reach and follow the vicinity of the maximum output point.

However, in the above-mentioned so-called mountain riding method, if the operating point is not constantly changed, the directionality is lost, and since ripple current and ripple voltage occur in the inverter, it is detected that the amount of change in the operating point is small. However, there is a problem in that the frequency of the inverter must be changed in an oscillating manner. Moreover, the control method is
Since the binary control (increase and decrease) by the sample section is performed, there is a problem that it is likely to become unstable and it is necessary to be careful in selecting the sample gap.

The present invention has been made to solve the above problems, and even if the optimum operating voltage of the solar cell changes due to temperature change, the operating point voltage setting is automatically changed following the change. Therefore, an object of the present invention is to obtain an output power adjustment device for a solar cell capable of stably obtaining the maximum output power.

[Means for solving problems]

The output power adjusting apparatus for a solar cell according to the present invention is a fluctuation signal output circuit that outputs a disturbance signal, and determines the maximum power value based on the voltage detection signal from the voltage detection means and the current detection signal from the current detection means. An adjustment circuit that outputs a voltage command corresponding to the maximum power value, a voltage command from the operation circuit, and a disturbance signal from the fluctuation signal output circuit are added to be output from the adjustment signal output means to the drive circuit. An adder circuit for correcting the signal and a disturbance signal are output from the fluctuation signal output circuit for a predetermined time every predetermined time according to the temperature change of the solar cell, and the voltage detection means and the current are output during the constant time. A timing control circuit that causes the detection means to detect voltage and current, and outputs a voltage command corresponding to the maximum power value obtained during the fixed time by the arithmetic circuit. The is provided with a regulating signal correcting means for holding until a predetermined time in accordance with the temperature change of the next solar cell.

[Action]

The present invention applies a disturbance every certain time gap (for example, several tens of minutes) to change the operating point of the solar cell,
Incorporate several sets of current values, find the voltage that maximizes the power from this, set this value as the voltage setting value until the next disturbance, and set the inverter so that the solar cell voltage becomes equal to this value. It controls the power control means of the power converter, such as the frequency and phase or the conduction ratio of the checker.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
FIG. 2 is a block diagram showing a configuration of an output power adjusting apparatus for a solar cell according to an embodiment of the present invention, and FIG. 2 is an output characteristic diagram showing an adjusting operation of an output power adjusting apparatus for a solar cell according to an embodiment of the present invention. FIG. 3 is a timing chart showing the operation of each part of the output power adjusting apparatus for a solar cell shown in FIG. Reference numbers 1 to 6, 8, 9, 12 in FIG.
16 are exactly the same as those shown in FIGS. 5 (a) and 5 (b), the description thereof will be omitted.

In FIG. 1, reference numeral 17 is a current detection means for detecting the output current of the solar cell 1, and 18 is an adjustment signal correction means, that is, an automatic voltage setting device. The automatic voltage setting device 18 includes a sampling A / D conversion circuit 19, a storage circuit 20, an arithmetic circuit 21,
Voltage command circuit 22, fluctuation signal output circuit, that is, disturbance generation circuit 2
3. It has an adder circuit 24 and a timing control circuit 25.

The sampling A / D conversion circuit 19 samples and takes in the voltage detection value output from the voltage detection means 6 and the current detection value output from the current detection means 17 for a predetermined period at regular intervals. The storage circuit 20 stores the data string sampled by the sampling A / D conversion circuit 19. The arithmetic circuit 21 obtains the power value from the voltage value and the current value of the data string stored in the storage circuit 20, respectively, and the voltage value when the maximum power value is obtained from the obtained power values. Calculate and output. The voltage command circuit 22 includes a D / A converter and outputs the voltage value when the maximum power value is obtained as a command value of the subsequent analog amount. The disturbance generating circuit 23 outputs a disturbance signal during the data sampling. The adder circuit 24 adds the output from the voltage command circuit 22 and the output from the disturbance generating circuit 23 and outputs the result. The timing control circuit 25,
The operation timing signals of the various circuits (memory circuit 20 and adder circuit 24) described above are generated and output respectively.

Reference numeral 26 is a PWM (pulse width modulation) circuit that generates a pulse train for operating each switch of the inverter 2a according to the frequency f and the voltage command V.

Next, the operation of the above configuration will be described below mainly with reference to the output characteristic diagram of the solar cell shown in FIG. 2 and the timing chart shown in FIG.

At time t ₀ shown in FIG. 3, the output setting signal 31 of the automatic voltage setting device 18 outputs the value of v ₁ . If the output voltage from the solar cell 1 detected by the voltage detecting means 6 is larger than v ₁ , the voltage control circuit 9 determines, according to the deviation value,
A signal is provided to the voltage / frequency converter 12 when increasing the frequency of the inverter 2a. At the same time, the voltage control circuit 9 gives a signal to the inverter output voltage setting unit 16 so that a voltage proportional to the frequency set by the voltage / frequency converter 12 is set. When the frequency is set by the voltage / frequency converter 12 and the voltage proportional to the frequency is set by the inverter output voltage setting device 16, the PWM circuit 26 is driven and the inverter 2a outputs the given frequency and The voltage corresponding to is output.
As a result, the motor 14 accelerates, the output increases, and the voltage of the solar cell 1 decreases and becomes equal to the set value v ₁ . In this way, the voltage of the solar cell 1 is always controlled to be equal to the setting signal 31 of the automatic voltage setting device 18.

Next, at time t ₁ , when the disturbance command 32 is given from the timing command circuit 25 to the disturbance generating circuit 23, the disturbance signal output from the disturbance generating circuit 23 is added to the output of the voltage command circuit 22 by the adding circuit 24 to set the output. Change signal 31 from v ₁ . (Note that the disturbance signal is changed in a ramp shape in FIG. 3, but it may be changed in a step shape.) As a result, the frequency of the inverter 2a changes and the frequency of the electric motor 14 changes as described above. As shown in Fig. 2, the operating point of the solar cell changes one after another. On the other hand, the timing control circuit 25 also issues a sampling command 33 at the same time, and the sampling A / D conversion circuit 19 sequentially determines the voltage value and current value of the solar cell 1 at this time (v ₁ , i ₁ ), ( v ₂ , i ₂ ) ...
Is stored and stored in the storage circuit 20 in a digital amount. The disturbance has ended and the data acquisition has ended. A calculation command 34 is issued from the timing control circuit 25 to the calculation circuit 21. In response to the operation command 34, the operation circuit 21 causes the storage circuit 20 to
The electric power (P _i
= V _i × i _i ) and the voltage value (v ₃ or v ₅ shown in FIG. 2) at the maximum power is calculated. After the calculation is completed, the voltage command circuit 22 converts the voltage value changed from v ₁ to v ₃ (= v ₅ ) into an analog signal and outputs it by the setting change command 35 output from the timing control circuit 25. At the same time, the voltage value is held until the next data sampling time comes.

Here, the time for outputting the disturbance signal, that is, the time T ₁ for sampling the data, is sufficient if the rotation of the electric motor 14 changes and the operating point of the solar cell 1 changes, so that several seconds is usually sufficient. Further, since the fluctuation of solar radiation is several seconds or more at the fastest, the characteristics of the solar cell 1 during the T ₁ period can be regarded as almost the same solar radiation condition.

On the other hand, since the temperature change of the solar cell is very slow, even if the period T is short, it is enough for several tens of minutes or more, and the period T is affected by the disturbance for data sampling.
T ₁ is short enough to ignore.

In the above-described embodiment of the present invention, the automatic voltage setting device 18 is shown individually for each functional circuit for convenience of explanation, but the timing control circuit 25 is input to the CPU as the sampling A / D conversion circuit 19. The voltage command circuit 22 equipped with a D / A converter is connected to the analog input port and the memory circuit 20 is connected to the analog output port.
If it is associated with a storage unit or the like, it can be configured by a normal microcomputer, and sequence control, power calculation and maximum value search, disturbance generation, etc. can be easily realized by a program (software).

Further, the one shown in FIG. 1 is one of the application examples of the present invention to the pump motor drive system using the variable frequency inverter 2a, but the output of the solar cell 1 is changed to another through the inverter 2. The present invention can be easily applied to the system shown in FIG. 5 (a) by supplying the power system 4 by removing the voltage setting device 7 and using the current detecting means 17 and the automatic voltage setting device 18. It is a thing.

Further, FIG. 4 shows another embodiment in which the present invention is applied to a DC load. In the figure, 41 is a general chip circuit, and 42 is an input / output circuit for adjusting the flow rate of the chip.
A control circuit for controlling the ratio of the output voltage, 14a is a DC motor. This embodiment is different from the above-mentioned embodiment only in that the output of the voltage control circuit 9 changes the distribution ratio of the chip instead of the frequency.

〔The invention's effect〕

As described above, according to the present invention, the maximum power value at the sampling time is obtained from the voltage detection signal and the current detection signal sampled for a certain period of time according to the temperature change of the solar cell, and the maximum power is obtained. A voltage value corresponding to the value is obtained and output, and the adjustment signal output from the adjustment signal output means to the drive circuit is corrected using the added value of the output signal and the fluctuation signal output during the sampling as a correction value. Therefore, even if the optimum operating voltage of the solar cell changes due to temperature changes, the operating point voltage setting will be automatically changed in accordance with the change, which will stabilize the maximum output power. There is an effect that a solar cell output power adjusting device that can be obtained is obtained. Further, since the optimum operating voltage is set after sampling for a certain period of time and the optimum operating voltage is held for a predetermined time according to the temperature change of the next solar cell, the output power does not fluctuate, It is possible to keep the value almost constant, and further, there is an effect that stable control can be performed without the control becoming unstable.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an output power adjusting apparatus for a solar cell according to an embodiment of the present invention, and FIG. 2 is a solar cell showing an adjusting operation of an output power adjusting apparatus for a solar cell according to an embodiment of the present invention. FIG. 3 is a timing chart showing the operation of each part of the output power adjustment apparatus for a solar cell shown in FIG. 1, and FIG. 4 is an output power adjustment for a solar cell according to another embodiment of the present invention. Block diagrams showing the configuration of the device, FIGS. 5 (a) and 5 (b) are block diagrams showing the configuration of the output power adjusting device of the conventional solar cell, and FIG. 6 is the above-mentioned FIG. 5 (a) and (b). FIG. 7B is an output characteristic diagram of the solar cell showing the adjustment operation of the device in FIG. In the figure, 1 is a solar cell, 2a is a variable voltage variable frequency inverter, 6 is voltage detection means, 9 is a voltage control circuit, 12 is a voltage / frequency converter, 14 is an AC motor, 14a is a DC motor, and 15 is a pump load. , 16 is an inverter output voltage setting device,
Reference numeral 17 is a current detecting means, and 18 is an automatic voltage setting device. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A voltage detecting means for detecting a voltage of a solar cell, a drive circuit connected to the solar cell for driving an output power of the solar cell to drive a load of the solar cell, and an output from the voltage detecting means. In the output power adjustment device for a solar cell, which has an adjustment signal output means for outputting an adjustment signal for adjusting the amount of passing electric power that passes through the drive circuit from the solar cell based on the detected signal, the output current of the solar cell A fluctuation signal output circuit for outputting a disturbance signal, and a maximum power value based on the voltage detection signal from the voltage detection means and the current detection signal from the current detection means and the maximum power value. A calculation circuit that outputs a voltage command corresponding to a power value, the voltage command from the calculation circuit, and the disturbance signal from the fluctuation signal output circuit are added to the adjustment signal output unit. From the variable signal output circuit for a fixed time every predetermined time according to the temperature change of the solar cell, and an adder circuit that uses a correction signal to correct the adjustment signal output from the drive circuit, It is composed of a timing control circuit that causes the voltage detection means and the current detection means to detect a voltage and a current during a certain period of time, and outputs an output of a voltage command corresponding to the maximum power value obtained during the certain period of time by the arithmetic circuit. An output power adjusting device for a solar cell, comprising an adjustment signal correcting means for holding the solar cell for a predetermined time according to the temperature change of the solar cell. 2. The output of the solar cell according to claim 1, wherein the drive circuit is an inverter circuit whose oscillation frequency is adjusted by an adjustment signal output from the adjustment signal output means. Power regulator. 3. The solar cell according to claim 1, wherein the drive circuit is a chopper circuit whose conduction ratio is adjusted by an adjustment signal output from the adjustment signal output means. Output power regulator.