JPH09325801A - Extreme value control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pursue the maximum or minimum value of an output signal with a simple constitution by holding both control and output signals to calculate the change value of them, multiplying these change value by each other and increasing or decreasing the number of output signals according to the positive and negative result of multiplication of both change value. SOLUTION: A 1st sample-and-hold circuit 2 fetches the control signals Vc at a proper sampling interval and holds these signal value. A 1st compactor 3 compares the output of the circuit 2 with the present signal Vc and calculates the change value ΔVc. A 2nd sample-and-hold circuit 4 holds the output signals Vout at a proper interval. A 2nd comparator 5 compares the output of the circuit 4 with the present signal Vout and calculates the change value ΔVout. A multiplier 6 multiplies the value ΔVc by the value ΔVout, and a control circuit 7 increases or decreases the number of signals Vc according to the positive or negative result Vx of the multiplication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extreme value control circuit applied to a system in which an output signal Vout has a maximum value or a minimum value with respect to a change in a control signal Vc.

[0002]

2. Description of the Related Art As shown in FIG.
In a system in which the output signal Vout takes the maximum value or the minimum value with respect to the change of c, it is often required to control the system so that the output signal Vout takes the maximum value or the minimum value. For example, the solar cell power generation system has a characteristic that the electric power greatly changes depending on the output voltage as shown in FIG. 8, and the operating point of the solar cell (the point on the characteristic curve of FIG. 8) is always matched with the maximum power point. Such control is required.

In such a case, the so-called "mountain climbing method" is mainly used in the past. This "mountain climbing method" is a control signal Vc
Is always minutely changed, the output signal Vout before and after the change is measured, and the control signal Vc is shifted in the direction in which the output signal Vout goes to the extreme value. However, in this method, since the control signal Vc is always moved by ΔVc, there is a problem that the fluctuation of the output signal Vout cannot be avoided and the control circuit becomes complicated and the cost is increased.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides an extreme value control circuit which can pursue the maximum value or the minimum value of the output signal Vout with a simple circuit configuration. It was done for good.

[0005]

The extreme value control circuit of the present invention made to solve the above problems is applied to a system in which the output signal Vout takes the maximum value or the minimum value with respect to the change of the control signal Vc. Which is an extreme value control circuit, and compares the output of this sampling and holding circuit with the current control signal Vc and a change amount ΔVc by comparing a first sampling and holding circuit which holds the control signal Vc at an appropriate sampling interval. The first comparator for calculation, the second sampling and holding circuit for holding the output signal Vout at an appropriate sampling interval, and the output of this sampling and holding circuit and the current output signal Vout are compared to calculate the variation ΔVout. A second comparator, a multiplier for multiplying these changes ΔVc and ΔVout, and a positive / negative sign of this multiplier. And a control circuit for increasing / decreasing the control signal Vc. Hereinafter, the present invention will be described in more detail.

[0006]

2 is a circuit diagram of an extreme value control circuit of the present invention, in which 1 is a controlled system, Vin is its input signal, and V is its input signal.
out is an output signal and Vc is a control signal. Reference numeral 2 is a first sampling and holding circuit for holding the control signal Vc, which takes in the control signal Vc at an appropriate sampling interval and holds the value thereof. 3 is a first comparator, which is a first sampling and holding circuit 2
And the current control signal Vc are compared to calculate the change ΔVc.

A second sampling and holding circuit 4 holds the output signal Vout at an appropriate sampling interval. The value is compared with the present output signal Vout in the second comparator 5 to calculate the variation ΔVout. The change ΔVc and the change ΔVout are multiplied by the multiplier 6, and the result Vx is input to the control circuit 7.

FIG. 3 is a graph in which time is plotted on the horizontal axis and a signal is plotted on the vertical axis. The sampling and holding circuit holds a constant value until the next sampling is performed.
In the process of increasing the signal, the current signal becomes larger than the sampling and holding signal, and the output of the comparator becomes positive, as shown in FIG. On the contrary, in the process of decreasing the signal, the current signal becomes smaller than the sampling hold signal, and the output of the comparator becomes negative. Therefore, the circuit in which the sampling hold circuit and the comparator shown in FIG. 4 are combined can accurately output the increase / decrease state of the signal, and by setting the sampling hold time appropriately, an extremely slow change can be achieved. It is possible to detect.

As shown in FIG. 5, the control signal Vc
In the system in which the output signal Vout takes the maximum value with respect to the change of, since ΔVc> 0 and ΔVout> 0 in the region of, Vx = ΔVc × ΔVout> 0. For this reason Vou
To maximize t, ΔVc> 0 may be maintained. In the next region, ΔVc> 0 and ΔVout <0, so Vx
<0, and it is necessary to set ΔVc to <0 in order to maximize Vout.

In the area shown in FIG. 6, Δ
Since Vc <0 and ΔVout> 0, Vx <0 and V
To make out the maximum value, ΔVc <0 may be maintained. In the further region, since ΔVc <0 and ΔVout <0, Vx> 0. Therefore, it is necessary to set ΔVc> 0 in order to maximize Vout. The above is summarized in Table 1.

[0011]

[Table 1]

As shown in Table 1, if the sign of Vx and the increase / decrease of the control signal Vc are the same, Vout converges to an extreme value. Therefore, if the control target system 1 is controlled by the control circuit 7 of FIG. 2, the system can be controlled so that Vout takes the maximum value. If necessary, an integral element or a proportional integral element can be inserted in the control circuit 7. Further, by appropriately selecting the polarity in accordance with the maximum and the minimum, it can be applied to all extreme value control.

[0013]

EXAMPLE Next, an example in which the extreme value control circuit of the present invention is applied to a solar cell power generation system will be shown. In FIG. 7, 11 is a multiplier for calculating the electric power P of the solar cell by multiplying the output voltage Vp of the solar cell and the output current Ip of the solar cell,
Reference numeral 12 is a sampling and holding circuit that holds the output of the multiplier 11, and 13 is a comparator. The sampling and holding circuit 12 is a circuit for sampling the output of the multiplier 11 at an appropriate sampling interval and holding the value Psh until the next sampling time. And the comparator 13
Compares the output Psh of the sampling and holding circuit 12 with the current power P of the solar cell, and outputs + if the current power P is larger and-if the current power P is smaller.

Further, 14 is a sampling and holding circuit for holding the output voltage Vp of the solar cell at an appropriate sampling interval, and 15 is a comparator. The comparator 15 compares the output Vsh of the sampling and holding circuit 14 with the current voltage Vp of the solar cell in the same manner as above, and outputs the current voltage Vp.
If the current voltage Vp is smaller than the current voltage Vp, + is output. Further 16 are these two comparators 1
Reference numeral 17 is a multiplier for multiplying the outputs of 3 and 15, and 17 is a P for performing proportional-integral control by the output of the multiplier 16.
I control circuit. Next, the operation of the above-described maximum power control circuit will be described with reference to the solar cell operation characteristic diagram of FIG.

FIG. 8 is a graph in which the horizontal axis represents the output voltage Vp of the solar cell and the vertical axis represents the output current Ip and output power P of the solar cell. As described above, the output of the multiplier 16 changes as shown in FIG. 8 depending on the position of the current operating point of the solar cell, and the output Vc of the multiplier 16 thus obtained is the PI control circuit 17 Entered in. Since this PI control circuit 7 outputs the sum of the input integral term and the proportional term, it continues to output the control signal corresponding to the integral term even when the maximum power point is reached and a stable state is reached.

FIG. 9 is a circuit diagram showing the entire solar power generation system, and the portion surrounded by a chain line corresponds to the circuit of the present invention shown in FIG. As shown in FIG. 9, the control signal, which is the output of the PI control circuit 17, is multiplied by the output of the full-wave rectifier circuit 18 of the system voltage, and compared with the triangular wave by the comparison circuit 19 at the next stage, and then the main switch 20 of the circuit. Create a PWM waveform that determines on / off.

In this solar power generation system, if the current operating point is on the path of or in FIG.
The PI input signal Vc becomes +, and it is necessary to increase the output voltage Vp of the solar cell on the characteristic curve. As is clear from the Ip characteristic curve of FIG. 8, it is necessary to reduce the output current Ip of the solar cell for this purpose. For this purpose, the ON duty, which is the ON / OFF ratio of the main switch 20, must be reduced. Therefore, the PI control circuit 17 has a PI
When the input signal Vc is +, the function of reducing the PI output and the duty factor is added. As a result, the main switch 20 decreases the output current Ip when the operating point is on the path of or in FIG.
Therefore, the output voltage Vp is increased to shift the operating point of the solar cell toward the maximum operating point.

On the contrary, if the current operating point is in the path of (8) in FIG. 8, the PI input signal Vc becomes-and it is necessary to reduce the output voltage Vp of the solar cell on the characteristic curve. For this purpose, the PI output is increased and the duty factor is increased to increase the output current Ip of the solar cell. As a result, when the operating point is on the path of or in FIG. 8, the main switch 20 increases the output current Ip, and thus decreases the output voltage Vp, and shifts the operating point of the solar cell toward the maximum operating point.

According to this embodiment, the maximum power tracking operation of the solar cell can be realized by a very simple analog circuit. The inverter circuit 21 always operates in connection with the electric power system while controlling the output current of the solar cell regardless of any fluctuation in the solar radiation amount of the solar cell. Moreover, there is an advantage that the output fluctuation can be reduced as compared with the hill-climbing method in which the maximum value or the minimum value is tracked while slightly moving the operating point using a microcomputer.

[0020]

As described above, according to the present invention, there is an advantage that the maximum value or the minimum value of the output signal Vout can be pursued by a very simple analog circuit.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a controlled system.

FIG. 2 is a circuit diagram of an extreme value control circuit of the present invention.

FIG. 3 is a graph showing a sampling hold signal.

FIG. 4 is a circuit diagram of a sampling and holding circuit and a comparator.

FIG. 5 is a graph showing changes in the output signal Vout with respect to changes in Vc.

FIG. 6 is a graph showing changes in the output signal Vout with respect to changes in Vc.

FIG. 7 is a circuit diagram of an extreme value control circuit according to an embodiment.

FIG. 8 is an operating characteristic diagram of a solar cell.

FIG. 9 is a circuit diagram showing a solar power generation system.

[Explanation of symbols]

 1 Control Target System 2 First Sampling and Holding Circuit 3 First Comparator 4 Second Sampling and Holding Circuit 5 Second Comparator 6 Multiplier 7 Control Circuit 11 Multiplier 12 Sampling and Holding Circuit 13 Comparator 14 Sampling and Holding 15 Comparator 16 Multiplier 17 PI control circuit 18 Full-wave rectifier circuit of system voltage 19 Comparison circuit 20 Main switch 21 Inverter circuit

Claims (1)

[Claims] 1. An extreme value control circuit applied to a system in which an output signal Vout takes a maximum value or a minimum value with respect to a change in the control signal Vc, the first value holding the control signal Vc at an appropriate sampling interval. Of the sampling and holding circuit, a first comparator for comparing the output of the sampling and holding circuit with the current control signal Vc to calculate the variation ΔVc, and a second comparator for holding the output signal Vout at an appropriate sampling interval. A sampling and holding circuit; a second comparator for calculating the change ΔVout by comparing the output of the sampling and holding circuit with the current output signal Vout; and a multiplier for multiplying the changes ΔVc and ΔVout. And a control circuit for increasing or decreasing the control signal Vc depending on whether the multiplier is positive or negative.