JPS6242213A - Output power controller for solar battery - Google Patents

Abstract

PURPOSE:To obtain the maximum output electric power with high stability by defining a voltage level at which the level of the electric power is maximum with addition of the disturbance as the set value and controlling a power control means so that the voltage level of a solar battery is equal to the set value. CONSTITUTION:When a disturbance command 32 is given from a timing command circuit 25, the disturbance signal is delivered from a disturbance generating circuit 23 and added with the output of a voltage command circuit 22 by an added circuit 24. Thus the output setting signal 31 is changed. As a result, the frequency of an inverter 2a is changed and therefore the frequency of a motor 14 is changed. Then the working points of a solar battery are changed sequentially. While the circuit 25 also delivers a sampling command 33 and a sampling A/D conversion circuit 19 fetches the voltage and current levels of the battery successively at that time point to store them in a storage circuit 20. Then the generation of disturbance is through, an arithmetic circuit 21 calculates the electric power from the data on the circuit 20 by an arithmetic command 35 to obtain the voltage value against the maximum electric power. When the arithmetic is over, the circuit 22 delivers the changed voltage value after converting it into the analog value by a setting change command and also holds this analog value until the next sampling operation.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention generally relates to an output power adjustment device for a solar cell,
More specifically, the present invention relates to an output power adjustment device for a solar cell equipped with a power converter such as an inverter or a chopper that supplies power to an AC or DC load.

[Conventional technology]

As is well known, the output of solar cells changes significantly depending on the amount of solar radiation, operating point voltage, or current, so it is necessary to always extract the maximum amount of power by adjusting the amount of load seen from the solar cells. .

However, even if solar radiation changes, the voltage that generates the maximum output of a solar cell does not change that much, so the load is adjusted so that the solar cell voltage becomes the voltage value (constant value) that generates the maximum output. Just adjust it. FIG. 5(a) is a block diagram showing an example of the configuration of a conventional solar cell output power adjustment device. The outline of the adjustment device is as follows. That is, a solar cell 1, a constant frequency inverter 2. transformer 3
When supplying power to another power system 4 via the voltage detecting means 6, the voltage of the solar cell 1 is detected, and the deviation between the detected voltage signal and the operating point voltage setting value by the voltage setting device 7 is added. After the voltage signal is determined by the voltage control circuit 9, a phase difference command signal δ between the voltage signal in the constant frequency inverter 2 and the voltage signal in the system 4 is outputted. Phase control circuit 1
0 is the output of the voltage/frequency converter 12, that is, the constant frequency, 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 is equal to the command value δ. Oscillation frequency of inverter 2 (
phase). In this case, the constant frequency inverter 2
Since the passing power of the constant frequency inverter 2 is adjusted according to the phase difference between the 0 output voltage signal and the voltage signal of the system 4, the voltage of the solar cell eventually operates at the optimal value set by the voltage setting device 7. I will do it. Note that 13 is a diode connected to prevent reverse current from the constant frequency inverter 2@. FIG. 5(b) is a block diagram showing another example of the configuration of a conventional solar cell output power adjustment device. The outline of the PL adjustment device is as follows. That is, the solar cell 1 is used as a power source, and the AC motor 1 is connected via a variable voltage variable frequency inverter 21 using pulse width modulation (PWM).
4 When driving the pump 15, the first stage of voltage detection 6
The voltage of the battery 1 is detected by the voltage control circuit 9f, and the variable voltage variable frequency inverter 2a
It was done to control the frequency of

The above-described control is performed by controlling the inverter 2 &
The load amount is adjusted by changing the rotation speed of the electric motor 140, and by such adjustment, it was possible to always obtain the maximum value of the y output from the solar cell 1. In this case, the output voltage setter 16 of the inverter 2a sets υ so that the output voltage from the inverter 2m is proportional to the frequency, and thereby the pulse width for operating each switch provided in the inverter 2& is set. is controlled (see Japanese Patent Laid-Open No. 132174/1983).

[Problem that the invention seeks to solve]

By the way, as shown in FIG. 6, if the temperature of the solar cell 1 changes, the maximum output point voltage (vop) will also change considerably.In the conventional output power adjustment device described above, the operating point is If it deviates, the output will drop rapidly, so the temperature (
It was necessary to change the voltage setting value according to Tj). or,
Care was required in selecting the set value, as the above-mentioned optimal voltage differs depending on the solar cell used.

Therefore, in consideration of these points, a method called the Shoryo Shandoshi method was devised as a method for automatically finding the maximum power point and operating at that point, despite changes 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 operating point of the solar cell is shifted by increasing or decreasing the frequency to change the amount of υ load.
The output of the solar cell at this point is measured and compared with the previous sample value. If the output increases, it is assumed that the direction of the frequency change is correct, and the frequency is changed in the same direction next time. On the other hand, if the output difference of the solar cells decreases, the direction of the frequency change is assumed to be the error p and is changed in the opposite direction, so that the maximum output point can be automatically reached and followed.

However, in the so-called multiplier method described above, if the operating point is not constantly changed, the directionality is lost, and ripple current and pull voltage are generated in the inverter, so there is little noise when the operating point changes. Detection is difficult, and as a result, there is a problem in that the frequency of the inverter always has to be oscillated. Furthermore, since the control method described above performs binary (increase and decrease) control based on the sample interval, there is a problem in that it is likely to become unstable and care must be taken in selecting the sample gap.

This invention was made to solve the above problems, and even if the optimum operating voltage of the υ solar cell changes due to temperature changes, the operating point voltage setting will automatically follow the change. It is an object of the present invention to obtain a solar cell output power adjustment device that can stably obtain maximum output power by being changed.

[Means for solving problems]

The solar cell output power III adjustment device according to the present invention detects the voltage of the solar cell with a voltage detection means, receives the output power of the solar cell connected to the solar cell trap, and controls the load of the solar cell with a drive circuit. In the device for outputting an adjustment signal t-Th signal ratio signal for adjusting the amount of electric power passing through the drive circuit from the solar cell based on the detection signal output from the voltage detection means, The output current of the battery is detected by a current detection means, and the maximum power value at the sampling time is determined from the voltage detection signal from the voltage detection means and the current detection signal from the current detection means sampled at predetermined time intervals. an arithmetic circuit that determines and outputs a voltage value corresponding to the maximum power value; a fluctuation signal output circuit that outputs a fluctuation signal during the sampling; an output signal from the arithmetic circuit and an output signal from the fluctuation signal output circuit; an addition circuit that adds the sum and supplies the resultant signal to the adjustment signal output means; .

[Effect]

This invention applies a disturbance every certain time interval (for example, several tens of minutes) to vary the operating point of the solar cell, and the voltage at this time,
Take in several sets of current values, find the voltage that maximizes the power from these, set this value as the voltage setting value until the next disturbance is applied, and set the inverter so that the voltage of the solar cell becomes equal to this value. It controls the power control means of the power converter, such as the frequency and phase of the power converter, or the chopper conduction rate.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a solar cell output power adjustment device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of a solar cell output power adjustment device according to an embodiment of the present invention. ! FIG. 3 is a timing chart showing the operation of each part of the solar cell output power adjusting device shown in FIG. 1.

Reference numbers 1 to 6, 8, 9, 12 to 16 in FIG. 1 are the same as those shown in FIG. 5(a) and FIG. 5(b), so the explanation thereof is Omitted.

In FIG. 1, reference numeral 17 is a current detection means for detecting the output current of the solar cell 1, and 1B is an adjustment signal correction means, that is, an automatic voltage setting device. The automatic voltage setter 18 includes a sampling/D conversion circuit 19, a storage circuit 20. It has an arithmetic circuit 21, a voltage command circuit 22, a fluctuation signal output circuit, that is, a disturbance generation circuit 23, an addition circuit 24, and a timing control circuit 25.

The sampling A/D conversion circuit 19 receives the voltage detection value output from the voltage detection means 6 and the current detection means 1T.
The current detection value output from the device is sampled and captured at regular intervals for a predetermined period. The storage circuit 20 stores nine data strings sampled by the sampling A/D conversion circuit 19. The arithmetic circuit 21 calculates power values from the voltage values and current values of the data string stored in the storage circuit 20, and calculates the voltage value when the maximum power value is obtained from among the calculated piezoelectric power values. Calculate and output. The voltage command circuit 22 includes a D/MU converter, and outputs the voltage value when the maximum power value is obtained as a command value for subsequent analog quantities. The disturbance generation circuit 23 outputs a disturbance signal of the data sampling. The addition circuit 24 adds the output from the voltage command circuit 22 and the output from the disturbance generation circuit 23 and outputs the sum. The timing control circuit 25 is configured to generate and output operation timing signals for the various circuits (memory circuit 20 and addition circuit 24) described above.

Note that reference number 26 is a PWM (pulse width modulation) circuit that generates a pulse train for operating each switch of the inverter 2a in accordance with the frequency f and the voltage command vK.

Next, the operation of the above configuration will be explained below, mainly using the output characteristic diagram of the solar cell shown in FIG. 2 and the timing chart shown in FIG. 3.

At time So illustrated in FIG. 3, the automatic voltage setting device 18
The output setting signal 31 outputs the value of vl. if,
If the output voltage from the solar cell 1 detected by the voltage detection means 6 is larger than vl, the voltage control circuit 9 causes the voltage/frequency converter 12 to increase the frequency of the inverter 2a according to the deviation value. give a signal. At the same time, the voltage control circuit 9 provides a signal to the inverter output voltage setter 16 so that a voltage proportional to the frequency set by the voltage/frequency converter 12 is set.

When a frequency is set by the voltage/frequency converter 12 and a voltage proportional to the frequency is set by the inverter output voltage setter 16, the PWM circuit 26 is driven and the inverter 2a is outputs the frequency and the corresponding voltage. As a result, the motor 14 accelerates, its output increases, and the voltage of the solar cell 1 decreases to become equal to the set value vIK. 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 t1, a disturbance command 3 is sent from the timing command circuit 25.
2 is given to the disturbance generation circuit 23, the disturbance generation circuit 23
The disturbance signal output from the adder circuit 24 is added to the output of the voltage command circuit 22 to change the output setting signal 31 from vl. (Although the disturbance signal is changed in a ramp-like manner in FIG. 3, it may also be changed in a step-like manner.) As a result, the frequency of the inverter 2& changes as described above, and the electric motor 14(2) As the frequency changes, the operating point of the solar cell changes one after another from ■, ■ to ◎, as shown in FIG. On the other hand, a sampling command 33 is also issued from the timing control circuit 25 at the same time, and the sampling A/
The D conversion circuit 19 converts the voltage value and current value of the solar cell 1 at this time into (vl, h ) + (721iz)...
and stores it in the storage circuit 2Q as a digital quantity.

When the disturbance generation ends υ and the data acquisition ends, the timing control circuit 25 issues a calculation command 34 to the calculation circuit 21.
is emitted. Based on the calculation command 34, the calculation circuit 21 calculates the stain force (P1=vlXii) from the voltage value data and current value data stored in the storage circuit 20, and also calculates the voltage value at maximum power (as shown in FIG. 2). v5 or 75). After the calculation is completed, the setting change command 35 is output from the timing control circuit 25, and the voltage command circuit 22 converts the voltage value changed from vl to the value of v>(=v+) into an analog signal and outputs it. At the same time, the voltage value is held until the next data sampling time comes.

Here, the time T1 for outputting the disturbance signal, that is, the time T1 for sampling data, is usually several seconds, which is sufficient for the TL moving device 14. Furthermore, since the solar radiation changes at its fastest rate of several seconds or more, the characteristics of the solar cell 1 during the T1 period can be considered to be under the same solar radiation conditions.

On the other hand, since the temperature change of solar cells is very slow, it is sufficient that the period T is at least several tens of minutes or more, and the period T is affected by disturbances for data sampling.
1 is so short that it can be ignored.

In the above-mentioned embodiment of the present invention, the automatic voltage setter 1B is shown individually for each functional circuit for convenience of explanation, but the timing control circuit 25 is connected to the CPUK sampling A.
/D conversion circuit 19f: D/D conversion circuit to the input analog input port.
By associating the voltage command circuit 22 with all the A converters with an analog output board and the memory circuit 20 with a memory section, etc., it can be configured with an ordinary microcomputer, and can perform sequence control, power calculation, maximum value checking, etc. The generation of disturbance can be easily realized by a program (software).

What is illustrated in FIG. 1 is one example of application of the present invention to a pump motor drive system using a variable frequency inverter 2a. In the system shown in FIG. 5(a), which is supplied to the electric power system 4, the voltage is removed by the voltage setting device 7, and the current detection means 17. By using the automatic voltage setting device 18, this invention can be easily applied.

Furthermore, FIG. 4 illustrates another embodiment in which the present invention is applied to a DC load. In the figure, 41 is a general chopper circuit, 42 is a chopper circuit that adjusts the current conductivity of the chopper, and A control circuit 14a that controls the ratio of output voltages is a DC motor. This embodiment differs from the previous embodiment only in that the output of the voltage control circuit 9 changes the current flow rate of the chopper in place of the frequency.

〔Effect of the invention〕

As described above, according to the present invention, the maximum power value at the sampling time is determined from the voltage detection signal and the current detection signal sampled at predetermined time intervals, and the voltage value corresponding to the maximum power value is determined and output. However, since the adjustment signal output from the adjustment signal output means to the drive circuit is corrected by using the addition value of the output signal and the fluctuation signal output during the sampling as a correction value, the adjustment signal output from the adjustment signal output means to the drive circuit is corrected. Even if the optimal operating voltage of the battery changes, the operating point voltage setting will be automatically changed to follow the change.This allows solar cells to stably obtain maximum output power. This has the effect of providing an output power adjustment device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a solar cell output power adjustment device according to an embodiment of the present invention, and FIG. 2 is a solar cell diagram showing the adjustment operation of the solar cell output power adjustment device according to an embodiment of the present invention. 3 is a timing chart showing the operation of each part of the solar cell output power adjustment device shown in FIG. 1, and FIG. 4 is a solar cell output power adjustment according to another embodiment of the present invention. FIGS. 5(1) and 5(b) are block diagrams showing the configuration of a conventional solar cell output power adjustment device, and FIG. 6 is a block diagram showing the configuration of the device, and FIG. ) is an output characteristic diagram of a solar cell showing the adjustment operation of the device. In the figure, 1 is a solar cell, 2a is a variable voltage variable frequency inverter, 6 is a voltage detection means, 9 is a voltage control circuit, 12 is a voltage/frequency converter, 14 is an AC motor, 14
a is a DC motor, 15 is a pump load, 16 is an inverter output voltage setter, 1T is a current detection means, and 18 is an automatic voltage setter. In each figure, the same reference numerals indicate the same or corresponding parts. Patent applicant Mitsubishi Electric Corporation (2 others) 2nd (I V5 V@V7... VOp 菟■SU 6rI!J (a) 8':3 Procedural amendment (voluntary)

Claims (3)

[Claims] (1) A voltage detection means for detecting the voltage of a solar cell; a drive circuit connected to the solar cell and receiving the output power of the solar cell to drive the load of the solar cell; and a voltage detection means for detecting the voltage of the solar cell; An output power adjustment device for a solar cell, comprising: an adjustment signal output means for outputting an adjustment signal for adjusting the amount of electric power passing from the solar cell through a drive circuit based on a detection signal, detecting the output current of the solar cell. A current detection means is provided to determine the maximum power value at the sampling time from the voltage detection signal from the voltage detection means sampled at predetermined time intervals and the current detection signal from the current detection means, and the maximum power value is determined by the maximum power value. an arithmetic circuit that calculates and outputs a corresponding power value; a fluctuation signal output circuit that outputs a fluctuating signal during the sampling; an output signal from the arithmetic circuit and an output signal from the fluctuating signal output circuit; 1. An output power adjustment device for a solar cell, comprising an addition circuit for supplying an adjustment signal to an adjustment signal output means, and comprising adjustment signal correction means for correcting an adjustment signal output from the adjustment signal output means to the drive circuit. (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 the 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 rate is adjusted by an adjustment signal output from the adjustment signal output means. Output power regulator.