JP2001178145A - Maximum power operating inverter system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in an AC output solar cell power generating system for taking out maximum power from solar cells and superimposing it on the power from an AC power supply, that the power conversion loss is increased because power is converted twice when a DC/DC converter having a maximum power point tracking function is combined with an inverter in order to realize maximum power point tracking and total efficiency of the power generating system is lowered. SOLUTION: Maximum power point tracking is realized without employing a DC/DC converter by keeping optimal operating conditions of an inverter from the waveform of pulse voltage and current generated from solar cells when the instantaneous output power from the inverter varies over time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC input / AC output inverter having a function of following a maximum power point for performing control so as to extract a large amount of power from a solar cell or the like.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram showing a configuration of a conventional AC output solar cell power generation system having a maximum power point tracking function.

A voltage and a current generated by the solar cell 1 are detected by a primary side voltage detector 31 and a primary side current detector 32, respectively, and an A / D converter 71, respectively.
The digital signals are converted into digital signals by a and 71b and input to the microcomputer unit 70. Further, the microcomputer unit 70 outputs a PWM signal generator 72.
The DC / DC converter 22 is driven by a pulse signal output from the PWM signal generator 72.

[0004] Inside the microcomputer unit 70, the product of the voltage and current generated from the solar cell 1 is calculated.
The power generated by the solar cell 1 is calculated. And P
By increasing or decreasing the command signal to the WM signal generator 72, the PWM
While examining the relationship between the value of the command signal to the signal generator 72 and the power generated by the solar cell 1, a command to the PWM signal generator 72 that maximizes the power generated by the solar cell 1 by a hill-climbing method or the like. By searching for the value of the signal, control of maximum power point tracking is realized.

[0005] DC power output from the DC / DC converter 22 is converted into AC by an inverter 23 and supplied to an AC power supply load 24.

[0006]

In a conventional AC output solar cell power generation system having a maximum power point tracking function, in order to maximize the power taken out of the solar cell 1,
The DC power is once converted by the DC / DC converter 22 into DC power, the maximum power point tracking is realized at that time, and then the power is converted into AC power by the inverter 23. Therefore, the power conversion is performed twice, and the power loss accompanying the power conversion is increased, and the efficiency of the entire AC output solar cell power generation system is reduced accordingly.

Further, in order to realize accurate maximum power point tracking, A / D converters 71a,
It was necessary to increase the resolution of 71b, which, together with the necessity of using a microcomputer, increased the cost of the converter control device having the function of maximum power point control.

In particular, in a home solar cell power generation system, the solar cell panel array often becomes partially shaded, and as one of effective measures for that,
There is a method of dividing a solar cell panel array into several parts and connecting a converter or an inverter having a function of following a maximum power point for each part. However, in order to realize this, it is necessary to reduce the cost of the converter and the control device of the inverter which increase in number. Therefore, it is desired that a control device for a converter or an inverter having a maximum power point tracking function be realized by a simple analog circuit or digital circuit without using a microcomputer or the like.

[0009]

FIG. 1 shows a first embodiment of the present invention. FIG. 1 is a configuration diagram of an AC output solar cell power generation system in which a solar cell 1 and an AC power supply load 24 are connected to a maximum power operation inverter system according to the present invention.

The first embodiment of the present invention comprises a smoothing capacitor 21, an inverter 23, a primary side voltage detector 31, a primary side current detector 32, an AC side voltage detector 33, an AC side current detector 34, Multipliers 41a and 41b, integrator 43, comparator 44a, signal amplifiers 45a and 45b, signal converter 46,
Sample hold 491a, 491b, peak detector 4
92a and 492b, and a current controller 73.

The command value amplitude change code signal 65 has H and L values.

The AC power supply load 24 is an AC power supply, and maintains an AC voltage without supplying power from the inverter 23.
Even when power is supplied from the inverter 23, the voltage does not change much.

The operation of the first embodiment is as follows.
FIG. 2 shows how each signal changes in the first embodiment.

The voltage of the AC power supply load 24 is detected by the AC side voltage detector 33, the signal magnitude is adjusted by the signal amplifier 45b, and then the product of the command value amplitude signal 66 and the multiplier 41b is calculated. It becomes a command value signal 67 which is a command value of the output current of the inverter 23. When the command value amplitude signal 66 has a substantially constant value, the command value of the output current of the inverter 23 has a waveform substantially proportional to the voltage of the AC power supply load 24.

The output current of the inverter 23 is detected by an AC side current detector 34 and input to a current controller 73. The current controller 73 compares the output current of the inverter 23 with a command value signal 67 that is a target value signal of the output current, and controls the inverter control signal 694 so that the output current of the inverter 23 and the value of the command value signal 67 become substantially equal. Is calculated and input to the inverter 23.

The waveform of the output power of the inverter 23 is shown in FIG.
The AC power supply load 2
It becomes a sine wave having a frequency twice as high as 4. Inverter 23
Has the same waveform as the AC-side supply power 693.

The smoothing capacitor 21 is connected to the input side of the inverter 23. Since the size of the smoothing capacitor 21 is finite, the input voltage to the inverter 23 is supplied to the AC side power supply 69.
3 and has a waveform like the primary side voltage signal 68.

The voltage and current generated by the solar cell 1 are
Each is detected by the primary-side voltage detector 31 and the primary-side current detector 32, and the product of the two is calculated by the multiplier 41a, and a power signal 62 indicating the power generated by the solar cell 1 is generated.

On the other hand, when the voltage generated by the solar cell 1 has positive and negative peaks with respect to time, the peak detector 4
The respective events are detected by 92a and 492b, and the values corresponding to the power generated by the solar cell 1 at the time of occurrence of those events are respectively stored in the sample and hold 49.
1a and 491b collect, hold, and output.

The value corresponding to the electric power generated by the solar cell 1 at the time when the voltage generated by the solar cell 1 has positive and negative peaks with respect to time is compared by the comparator 44a. , Is output as a command value amplitude change code signal 65.

It is assumed that the width of the periodic change of the voltage generated by solar cell 1 is small. Then, when the voltage generated by the solar cell 1 periodically fluctuates around a voltage that is at least somewhat higher than the voltage at which the power generated by the solar cell 1 is maximized, the voltage generated by the solar cell 1 changes with respect to time. The power generated by the solar cell 1 at the time when the positive peak is generated is smaller than the power generated by the solar cell 1 at the time when the voltage generated by the solar cell 1 generates a negative peak with respect to time. On the other hand, when the voltage generated by the solar cell 1 periodically fluctuates around a voltage that is lower than the voltage at which the power generated by the solar cell 1 becomes maximum to some extent, the voltage generated by the solar cell 1 On the other hand, the electric power generated by the solar cell 1 at the time when the positive peak occurs is larger than the electric power generated by the solar cell 1 at the time when the voltage generated by the solar cell 1 generates a negative peak with respect to time. .

The voltage generated by the solar cell 1 is
The command value change code signal 65 has the value of H when the power fluctuates around a voltage that is higher than the voltage at which the generated power becomes maximum to some extent. Then, the command value change code signal 65 is converted into a signal having a positive value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66 output from the integrator 43 rises. As a result, the average power converted by the inverter 23 increases, so that the average input current of the inverter 23 increases, and the average current generated by the solar cell 1 increases. Then, when the average voltage generated by the solar cell 1 decreases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized.

On the other hand, when the voltage generated by the solar cell 1 periodically fluctuates around a voltage that is lower than the voltage at which the power generated by the solar cell 1 is maximized to a certain extent, the command value change code signal 65 becomes It has the value of L. Then, the command value change code signal 65 is converted into a signal having a negative value by the signal converter 46, and then integrated by the integrator 43, and
3, the value of the command value amplitude signal 66 decreases, and as a result, the average power converted by the inverter 23 decreases. Therefore, the average input current of the inverter 23 decreases, and the average current generated by the solar cell 1 decreases. Descend. And solar cell 1
Rises in the average voltage at which the solar cell 1
Is periodically fluctuated around a value close to the voltage at which the power generated by the solar cell 1 is maximized.

In the first embodiment, the inverter system is controlled so that the voltage generated by the solar cell 1 fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized. From the voltage and current generated by the solar cell 1, the average output power of the corresponding inverter 23 is estimated in consideration of the conversion loss and the like in the inverter 23, and the inverter system is controlled so as to maximize the average output power of the inverter 23. May be.

In the first embodiment, the power generated by the solar cell 1 at the time when the voltage generated by the solar cell 1 has a peak with respect to time is collected.
The power generated by the solar cell 1 at the time when the current generated by the solar cell 1 has a peak with respect to time may be collected, or the amount determined by the voltage and current generated by the solar cell 1 may have a peak with respect to time. The power generated by the solar cell 1 may be collected.

In the first embodiment, the inverter 23
Has been performed by controlling the amplitude of the current output by the inverter 23, but may be performed by controlling the amplitude of the voltage output by the inverter 23, or by controlling the amplitude of the voltage output by the inverter 23. This may be performed by controlling the amplitude.

FIG. 3 shows a second embodiment of the present invention. FIG.
1 is a configuration diagram of an AC output solar cell power generation system in which a solar cell 1 and an AC power supply load 24 are connected to the maximum power operation inverter system according to the present invention.

The second embodiment of the present invention comprises a smoothing capacitor 21, an inverter 23, a primary side voltage detector 31, a primary side current detector 32, an AC side voltage detector 33, an AC side current detector 34, Multipliers 41a and 41b, differentiators 42a and 42
b, integrator 43, comparators 44a and 44b, signal amplifier 4
5a, 45b, 45c, a signal converter 46, an exclusive OR gate 52, and a current controller 73.

The comparator outputs 64a and 64b and the command value amplitude change code signal 65 have H and L values.

The AC power supply load 24 is an AC power supply, and maintains an AC voltage without supplying power from the inverter 23.
Even when power is supplied from the inverter 23, the voltage does not change much.

The operation of the second embodiment is as follows.
FIG. 4 shows how each signal changes in the second embodiment.

The voltage of the AC power supply load 24 is detected by the AC side voltage detector 33, the signal amplitude is adjusted by the signal amplifier 45b, and then the product of the command value amplitude signal 66 is calculated by the multiplier 41b. It becomes a command value signal 67 which is a command value of the output current of the inverter 23. When the command value amplitude signal 66 has a substantially constant value, the command value of the output current of the inverter 23 has a waveform substantially proportional to the voltage of the AC power supply load 24.

The output current of the inverter 23 is detected by the AC side current detector 34 and input to the current controller 73. The current controller 73 compares the output current of the inverter 23 with a command value signal 67 that is a target value signal of the output current, and controls the inverter control signal 694 so that the output current of the inverter 23 and the value of the command value signal 67 become substantially equal. Is calculated and input to the inverter 23.

The waveform of the output power of the inverter 23 is shown in FIG.
The AC power supply load 2
It becomes a sine wave having a frequency twice as high as 4. Inverter 23
Has the same waveform as the AC-side supply power 693.

Although the smoothing capacitor 21 is connected to the input side of the inverter 23, the input voltage to the inverter 23 is limited to the AC side power 69
3 and has a waveform like the primary side voltage signal 68.

The voltage and current generated by the solar cell 1 are
Each is detected by the primary-side voltage detector 31 and the primary-side current detector 32, and the product of the two is calculated by the multiplier 41a, and a power signal 62 indicating the power generated by the solar cell 1 is generated. After adjusting the signal level and the like through the signal amplifier 45a, the power signal 62 is converted into a time differential value by the differentiator 42a, and further converted into a signal having a sign of the time differential value by the comparator 44a. When the power generated by the solar cell 1 rises with time, the comparator output 64a takes a value of H, and when it falls, it takes a value of L.

On the other hand, the primary voltage signal 68, which is a signal corresponding to the voltage generated by the solar cell 1, is converted in level by the signal amplifier 45c and then converted into a time differential value by the differentiator 42b. The sign is converted by the comparator 44b into the sign of the value of the time derivative. When the voltage generated by the solar cell 1 increases with time, the comparator output 6
4b takes the value of H, and takes the value of L when it is falling.

The comparator output 64a and the comparator output 64b are
The signal is input to the exclusive OR gate 52, and the signal of the exclusive OR of both signals is output as the command value amplitude change code signal 65.

It is assumed that the width of the periodic change of the voltage generated by solar cell 1 is small. Then, when the voltage generated by the solar cell 1 periodically fluctuates in a sinusoidal manner around a voltage that is higher than the voltage at which the power generated by the solar cell 1 becomes maximum to a certain degree or more, the voltage generated by the solar cell 1 becomes In the time that rises with time, the time that the power generated by the solar cell 1 rises with time is shorter than the time that the power that the solar cell 1 generates falls with time, and the voltage that the solar cell 1 generates decreases with time. The time during which the power generated by the solar cell 1 rises over time is longer than the time during which the power generated by the solar cell 1 falls over time.

On the other hand, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is lower than the voltage at which the power generated by the solar cell 1 becomes maximum to a certain extent or more, the solar cell 1 In the time when the generated voltage rises with time, the time when the power generated by the solar cell 1 rises with time is longer than the time when the power generated by the solar cell 1 falls with time, and the solar cell 1 is generated. In the time when the voltage generated decreases with time, the time when the power generated by the solar cell 1 increases with time is shorter than the time when the power generated by the solar cell 1 decreases with time.

Therefore, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is somewhat higher than the voltage at which the power generated by the solar cell 1 is maximized, the command value change code signal The time when 65 has the value of H is longer than the time when it has the value of L. The command value change code signal 65 is converted into a signal having a positive or negative value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66, which is the output of the integrator 43, increases because the time longer than the time having the value. As a result, the average power converted by the inverter 23 increases, so that the average input current of the inverter 23 increases. Then, the average current generated by the solar cell 1 increases. Then, when the average voltage generated by the solar cell 1 decreases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized.

On the other hand, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is lower than the voltage at which the power generated by the solar cell 1 is maximized to a certain extent, the command value change code The time when the signal 65 has the value of H is L
Is shorter than the time with the value of The command value change code signal 65 is converted into a signal having a positive or negative value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66, which is the output of the integrator 43, falls because the time is shorter than the time having the value. As a result, the average power converted by the inverter 23 decreases, so that the average input current of the inverter 23 decreases. Then, the average current generated by the solar cell 1 decreases. Then, as the average voltage generated by the solar cell 1 increases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to a voltage at which the power generated by the solar cell 1 is maximized.

In the second embodiment, the inverter system is controlled such that the voltage generated by the solar cell 1 fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized. From the voltage and current generated by the solar cell 1, the average output power of the corresponding inverter 23 is estimated in consideration of the conversion loss and the like in the inverter 23, and the inverter system is controlled so as to maximize the average output power of the inverter 23. May be.

In the second embodiment, the exclusive OR of the sign of the time derivative of the power generated by the solar cell 1 and the sign of the time derivative of the voltage generated by the solar cell 1 is used. Of time derivative of electric power generated by solar cell 1
The exclusive OR of the sign of the time derivative of the current generated by the solar cell 1 may be used, or the sign of the time derivative of the power generated by the solar cell 1 and the amount of the time derivative determined by the voltage and current generated by the solar cell 1 may be used. Exclusive OR of codes may be used.
At this time, the polarity of the input / output characteristics of the signal converter 46 needs to be set appropriately.

In the second embodiment, the inverter 23
Has been performed by controlling the amplitude of the current output by the inverter 23, but may be performed by controlling the amplitude of the voltage output by the inverter 23, or by controlling the amplitude of the voltage output by the inverter 23. This may be performed by controlling the amplitude.

FIG. 5 shows a third embodiment of the present invention. FIG.
1 is a configuration diagram of an AC output solar cell power generation system in which a solar cell 1 and an AC power supply load 24 are connected to the maximum power operation inverter system according to the present invention.

The third embodiment of the present invention comprises a smoothing capacitor 21, an inverter 23, a primary side voltage detector 31, a primary side current detector 32, an AC side voltage detector 33, an AC side current detector 34, Multipliers 41a, 41b, differentiator 42a, integrator 43, comparators 44a, 44b, signal amplifiers 45a, 4
5b, 45c, signal converter 46, DC cutoff filter 49
4, a D-flip-flop 51 and a current controller 73.

The comparator outputs 64a and 64b and the command value amplitude change code signal 65 have H and L values.

The AC power supply load 24 is an AC power supply, and maintains an AC voltage without supplying power from the inverter 23.
Even when power is supplied from the inverter 23, the voltage does not change much.

The operation of the third embodiment is as follows.
FIG. 6 shows how each signal changes in the third embodiment.

After the voltage of the AC power supply load 24 is detected by the AC side voltage detector 33 and the signal amplitude is adjusted by the signal amplifier 45b, the product of the command value amplitude signal 66 and the multiplier 41b is calculated by the multiplier 41b. It becomes a command value signal 67 which is a command value of the output current of the inverter 23. When the command value amplitude signal 66 has a substantially constant value, the command value of the output current of the inverter 23 has a waveform substantially proportional to the voltage of the AC power supply load 24.

The output current of the inverter 23 is detected by the AC side current detector 34 and input to the current controller 73. The current controller 73 compares the output current of the inverter 23 with a command value signal 67 that is a target value signal of the output current, and controls the inverter control signal 694 so that the output current of the inverter 23 and the value of the command value signal 67 become substantially equal. Is calculated and input to the inverter 23.

The waveform of the output power of the inverter 23 is shown in FIG.
The AC power supply load 2
It becomes a sine wave having a frequency twice as high as 4. Inverter 23
Has the same waveform as the AC-side supply power 693.

Although the smoothing capacitor 21 is connected to the input side of the inverter 23, the input voltage to the inverter 23 is limited to the AC side power 69
3 and has a waveform like the primary side voltage signal 68.

The voltage and current generated by the solar cell 1 are
Each is detected by the primary-side voltage detector 31 and the primary-side current detector 32, and the product of the two is calculated by the multiplier 41a, and a power signal 62 indicating the power generated by the solar cell 1 is generated. After adjusting the signal level and the like through the signal amplifier 45a, the power signal 62 is converted into a time differential value by the differentiator 42a, and further converted into a signal having a sign of the time differential value by the comparator 44a. When the power generated by the solar cell 1 rises with time, the comparator output 64a takes a value of H, and when it falls, it takes a value of L.

On the other hand, the primary side voltage signal 68, which is a signal corresponding to the voltage generated by the solar cell 1, has its level etc. converted by the signal amplifier 45 c, and then a DC cutoff filter 494.
, The DC component is cut off, and the waveform is further shaped by the comparator 44b to generate a comparator output 64b. When the voltage generated by the solar cell 1 crosses the average value of the voltage generated by the solar cell 1 from small to large, the comparator output 64
b changes from L to H.

The D-flip-flop 51 outputs the comparator output 6 at the moment when the comparator output 64b changes from L to H.
The value of 4a is sampled and output as a command value amplitude change code signal 65, which is then held until the comparator output 64b changes from L to H.

It is assumed that the width of the periodic change of the voltage generated by solar cell 1 is small. Then, when the voltage generated by the solar cell 1 periodically fluctuates in a sinusoidal manner around a voltage that is higher than the voltage at which the power generated by the solar cell 1 becomes maximum to a certain degree or more, the voltage generated by the solar cell 1 becomes At the moment when the average value crosses in the direction from small to large, the power generated by the solar cell 1 decreases with time.

On the other hand, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is lower than the voltage at which the power generated by the solar cell 1 becomes maximum to a certain extent or more, the solar cell 1 At the moment when the generated voltage crosses the average value in the direction from small to large, the power generated by the solar cell 1 increases with time.

Therefore, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is at least somewhat higher than the voltage at which the power generated by the solar cell 1 is maximized, the command value change code signal 65 has the value of H.
Then, the command value change code signal 65 is converted into a signal having a positive value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66 output from the integrator 43 rises. As a result, the average power converted by the inverter 23 increases, so that the average input current of the inverter 23 increases, and the average current generated by the solar cell 1 increases. Then, when the average voltage generated by the solar cell 1 decreases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized.

On the contrary, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage lower than the voltage at which the power generated by the solar cell 1 is at least a certain value, the command value change code The signal 65 has the value of L. Then, the command value change code signal 65 is converted into a signal having a negative value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66 output from the integrator 43 decreases, As a result, the average power converted by the inverter 23 decreases, so that the average input current of the inverter 23 decreases, and the average current generated by the solar cell 1 decreases. Then, as the average voltage generated by the solar cell 1 increases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to a voltage at which the power generated by the solar cell 1 is maximized.

In the third embodiment, the inverter system is controlled such that the voltage generated by the solar cell 1 fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized. From the voltage and current generated by the solar cell 1, the average output power of the corresponding inverter 23 is estimated in consideration of the conversion loss and the like in the inverter 23, and the inverter system is controlled so as to maximize the average output power of the inverter 23. May be.

In the third embodiment, the sign of the time derivative of the power generated by the solar cell 1 at the moment when the voltage generated by the solar cell 1 crosses the average value in the direction from small to large is used. The sign of the time derivative of the power generated by the solar cell 1 at the moment when the voltage generated by the solar cell 1 crosses the average value in the direction from large to small may be used, or the voltage generated by the solar cell 1 may be the average value. Each sign of the time derivative of the power generated by the solar cell 1 at each moment of traversing the value in each direction from small to large and from large to small may be used.

In the third embodiment, the sign of the time derivative of the electric power generated by the solar cell 1 at the moment when the voltage generated by the solar cell 1 crosses the average value is used. The sign of the time derivative of the power generated by the solar cell 1 at the moment when the current crosses the average value may be used, or the solar cell at the moment when the amount determined by the voltage and current generated by the solar cell 1 crosses the average value. The sign of the time derivative of the power generated by 1 may be used.
At this time, the polarity of the input / output characteristics of the signal converter 46 needs to be set appropriately.

In the third embodiment, when the sign of the time derivative of the power generated by the solar cell 1 at the moment when the voltage generated by the solar cell 1 crosses the average value in the direction from small to large is positive, At the moment when the sign of the time derivative of the power generated by the battery 1 changes from positive to negative, the voltage generated by the solar cell 1 becomes larger than its average value. Conversely, when the sign of the time derivative of the power generated by the solar cell 1 at the moment when the voltage generated by the solar cell 1 crosses the average value in the direction from small to large is negative, the time of the power generated by the solar cell 1 The voltage generated by the solar cell 1 at the moment when the sign of the differentiation changes from positive to negative becomes smaller than its average value.

Therefore, in the third embodiment, the sign of the time derivative of the power generated by the solar cell 1 at the moment when the voltage generated by the solar cell 1 crosses the average value is used. The sign of the difference between the voltage or current generated by the solar cell 1 or its average value determined by the voltage and current at the moment when the sign of the time derivative of the generated power changes from positive to negative may be used.

In the third embodiment, the inverter 23
Has been performed by controlling the amplitude of the current output by the inverter 23, but may be performed by controlling the amplitude of the voltage output by the inverter 23, or by controlling the amplitude of the voltage output by the inverter 23. This may be performed by controlling the amplitude.

FIG. 7 shows a fourth embodiment of the present invention. FIG.
1 is a configuration diagram of an AC output solar cell power generation system in which a solar cell 1 and an AC power supply load 24 are connected to the maximum power operation inverter system according to the present invention.

The fourth embodiment of the present invention comprises a smoothing capacitor 21, an inverter 23, a primary side voltage detector 31, a primary side current detector 32, an AC side voltage detector 33, an AC side current detector 34, Multipliers 41a, 41b, differentiator 42a, integrator 43, comparators 44a, 44b, signal amplifiers 45a, 4
5b, a signal converter 46, a D-flip-flop 51, and a current controller 73.

The comparator outputs 64a, 64b and the command value amplitude change code signal 65 have H and L values.

The AC power supply load 24 is an AC power supply, and maintains an AC voltage without supplying power from the inverter 23.
Even when power is supplied from the inverter 23, the voltage does not change much.

The operation of the fourth embodiment is as follows.
FIG. 8 shows how each signal changes in the fourth embodiment.

The voltage of the AC power supply load 24 is detected by the AC side voltage detector 33, the signal amplitude is adjusted by the signal amplifier 45b, and the product of the command value amplitude signal 66 and the multiplier 41b is calculated by the multiplier 41b. It becomes a command value signal 67 which is a command value of the output current of the inverter 23. When the command value amplitude signal 66 has a substantially constant value, the command value of the output current of the inverter 23 has a waveform substantially proportional to the voltage of the AC power supply load 24.

The output current of the inverter 23 is detected by the AC side current detector 34 and input to the current controller 73. The current controller 73 compares the output current of the inverter 23 with a command value signal 67 that is a target value signal of the output current, and controls the inverter control signal 694 so that the output current of the inverter 23 and the value of the command value signal 67 become substantially equal. Is calculated and input to the inverter 23.

The waveform of the output power of the inverter 23 is shown in FIG.
The AC power supply load 2
It becomes a sine wave having a frequency twice as high as 4. Inverter 23
Has the same waveform as the AC-side supply power 693.

Although the smoothing capacitor 21 is connected to the input side of the inverter 23, the input voltage to the inverter 23 is limited to the AC side power 69
3 and has a waveform like the primary side voltage signal 68.

The voltage and current generated by the solar cell 1 are
Each is detected by the primary-side voltage detector 31 and the primary-side current detector 32, and the product of the two is calculated by the multiplier 41a, and a power signal 62 indicating the power generated by the solar cell 1 is generated. After adjusting the signal level and the like through the signal amplifier 45a, the power signal 62 is converted into a time differential value by the differentiator 42a, and further converted into a signal having a sign of the time differential value by the comparator 44a. When the power generated by the solar cell 1 rises with time, the comparator output 64a takes a value of H, and when it falls, it takes a value of L.

On the other hand, the voltage of the AC power supply load 24 detected by the AC side voltage detector 33 is adjusted in signal magnitude by the signal amplifier 45b, and then shaped by the comparator 44b to generate a comparator output 64b. Is done. At the moment when the voltage of the AC power supply load 24 is zero, the output power of the inverter 23 becomes zero, so that the value of the comparator output 64b becomes L
The event that changes from H to H corresponds to every other event in which the output power of the inverter 23 has a negative peak with respect to time.

The D flip-flop 51 outputs the comparator output 6 at the moment when the comparator output 64b changes from L to H.
The value of 4a is sampled and output as a command value amplitude change code signal 65, which is then held until the comparator output 64b changes from L to H.

It is assumed that the capacity of the smoothing capacitor 21 is large to some extent, and the width of the voltage generated by the solar cell 1 that fluctuates periodically is small. Then, the timing at which the output power of the inverter 23 has a negative peak with respect to time is substantially equal to the timing at which the voltage generated by the solar cell 1 crosses the average value in the direction from small to large.

When the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is somewhat higher than the voltage at which the power generated by the solar cell 1 becomes maximum, the generation of the solar cell 1 occurs. At the moment when the applied voltage crosses the average value in the direction from small to large, the power generated by the solar cell 1 decreases with time.

Conversely, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is at least somewhat lower than the voltage at which the power generated by the solar cell 1 is maximized, the solar cell 1 At the moment when the generated voltage crosses the average value in the direction from small to large, the power generated by the solar cell 1 increases with time.

Therefore, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is at least somewhat higher than the voltage at which the power generated by the solar cell 1 is maximized, the command value change code signal 65 has the value of H.
Then, the command value change code signal 65 is converted into a signal having a positive value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66 output from the integrator 43 rises. As a result, the average power converted by the inverter 23 increases, so that the average input current of the inverter 23 increases, and the average current generated by the solar cell 1 increases. Then, when the average voltage generated by the solar cell 1 decreases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized.

On the contrary, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage lower than the voltage at which the power generated by the solar cell 1 becomes maximum to some extent, the command value change code The signal 65 has the value of L. Then, the command value change code signal 65 is converted into a signal having a negative value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66 output from the integrator 43 decreases, As a result, the average power converted by the inverter 23 decreases, so that the average input current of the inverter 23 decreases, and the average current generated by the solar cell 1 decreases. Then, as the average voltage generated by the solar cell 1 increases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to a voltage at which the power generated by the solar cell 1 is maximized.

In the fourth embodiment, the inverter system is controlled so that the voltage generated by the solar cell 1 fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized. From the voltage and current generated by the solar cell 1, the average output power of the corresponding inverter 23 is estimated in consideration of the conversion loss and the like in the inverter 23, and the inverter system is controlled so as to maximize the average output power of the inverter 23. May be.

In the fourth embodiment, the AC power supply load 2
4 uses the sign of the time derivative of the power generated by the solar cell 1 at the moment when the sign of the voltage changes from negative to positive. However, the solar cell at the moment when the sign of the voltage of the AC power supply load 24 changes from positive to negative. The sign of the time derivative of the power generated by the battery 1 may be used, or the time of the power generated by the solar cell 1 at each moment when the sign of the voltage of the AC power supply load 24 changes from negative to positive and from positive to negative. The sign of each derivative may be used.

In the fourth embodiment, the AC power supply load 2
Although the sign of the time derivative of the power generated by the solar cell 1 at the moment when the sign of the voltage 4 changes from negative to positive is used, the power of the solar cell 1 at the moment when the output current of the inverter 23 crosses zero is used. The sign of the time derivative may be used, or the sign of the time derivative of the power generated by the solar cell 1 at the moment when the amount determined by the output voltage and the output current of the inverter 23 crosses zero may be used. The sign of the time derivative of the power generated by the solar cell 1 at the time when the current is close to zero may be used.

Further, detecting that the voltage determined by the voltage of the AC power supply load 24, the output current of the inverter 23, or the output voltage and the output current of the inverter 23 has a positive or negative or positive and negative peak with respect to time. Thus, a positive peak of the output power of the inverter 23 with respect to time may be detected, and the sign of the time derivative of the power generated by the solar cell 1 at the moment when the peak is detected may be used. May be used as the sign of the time derivative of the power generated by the solar cell 1 at the time at which the signal has a positive peak with respect to time. At this time, the polarity of the input / output characteristics of the signal converter 46 needs to be set appropriately.

Further, the output power of the inverter 23 is detected by some means, and a positive or negative or positive and negative peak with respect to the time of the output power is detected, and the solar cell 1 is generated at the moment when the peak is detected. The sign of the time derivative of the power to be applied may be used.

Further, it is detected from inverter control signal 694 that the output power of inverter 23 has a positive or negative or positive and negative peak with respect to time, and solar cell 1 at the moment when the peak is detected. The sign of the time derivative of the generated power may be used.

In the fourth embodiment, when the sign of the time derivative of the power generated by the solar cell 1 at the moment when the output voltage or the output current of the inverter 23 crosses zero is positive, the time of the power generated by the solar cell 1 At the moment when the sign of the derivative changes from positive to negative, the sign of the product of the output voltage or output current of the inverter 23 and its time derivative becomes positive. Conversely, when the sign of the time derivative of the power generated by the solar cell 1 at the moment when the output voltage or the output current of the inverter 23 crosses zero is negative, the sign of the time derivative of the power generated by the solar cell 1 changes from positive to negative. At the moment of the change, the sign of the product of the output voltage or output current of the inverter 23 and its time derivative becomes negative.

Therefore, in the fourth embodiment, the sign of the time derivative of the power generated by the solar cell 1 at the moment when the output voltage or the output current of the inverter 23 crosses zero is used. At the moment when the sign of the time derivative of the power changes from positive to negative, the output voltage or output current of the inverter 23 or the sign of the amount determined by the output voltage and the output current and the value of the exclusive OR of the sign of the time derivative are used. Alternatively, at the moment when the sign of the time derivative of the power generated by the solar cell 1 changes from positive to negative, the output voltage or the output current of the inverter 23 or the product of the amount determined by the output voltage and the output current and the time derivative thereof May be used.

In the fourth embodiment, the inverter 23
Has been performed by controlling the amplitude of the current output by the inverter 23, but may be performed by controlling the amplitude of the voltage output by the inverter 23, or by controlling the amplitude of the voltage output by the inverter 23. This may be performed by controlling the amplitude.

FIG. 9 shows a fifth embodiment of the present invention. FIG.
1 is a configuration diagram of an AC output solar cell power generation system in which a solar cell 1 and an AC power supply load 24 are connected to the maximum power operation inverter system according to the present invention.

The fifth embodiment of the present invention comprises a smoothing capacitor 21, an inverter 23, an AC power supply load 24, a primary side voltage detector 31, a primary side current detector 32, an AC side voltage detector 33, an AC side Current detector 34, multipliers 41a and 41b,
Integrator 43, comparators 44a and 44b, signal amplifier 45
a, 45b, a signal converter 46, a reference voltage 48, a track hold 493, an absolute value circuit 495, a D-flip-flop 51, and a current controller 73.

The comparator outputs 64a and 64b and the command value amplitude change code signal 65 have H and L values.

The AC power supply load 24 is an AC power supply, and maintains an AC voltage without supplying power from the inverter 23.
Even when power is supplied from the inverter 23, the voltage does not change much.

The operation of the fifth embodiment is as follows.
FIG. 10 shows how each signal changes in the fifth embodiment.

The voltage of the AC power supply load 24 is detected by the AC side voltage detector 33, the signal amplitude is adjusted by the signal amplifier 45b, and then the product of the command value amplitude signal 66 and the multiplier 41b is calculated. It becomes a command value signal 67 which is a command value of the output current of the inverter 23. When the command value amplitude signal 66 has a substantially constant value, the command value of the output current of the inverter 23 has a waveform substantially proportional to the voltage of the AC power supply load 24.

The output current of the inverter 23 is detected by the AC side current detector 34 and is input to the current controller 73. The current controller 73 compares the output current of the inverter 23 with a command value signal 67 that is a target value signal of the output current, and controls the inverter control signal 694 so that the output current of the inverter 23 and the value of the command value signal 67 become substantially equal. Is calculated and input to the inverter 23.

The waveform of the output power of the inverter 23 is shown in FIG.
As shown by the AC side supply power 693 of 0, the sine wave has a frequency twice that of the AC power supply load 24. Inverter 2
3 has substantially the same waveform as the AC-side supply power 693.

Although the smoothing capacitor 21 is connected to the input side of the inverter 23, the input voltage to the inverter 23 is limited to the AC side power 69
3 and has a waveform like the primary side voltage signal 68.

The voltage and current generated by the solar cell 1 are
Each is detected by the primary-side voltage detector 31 and the primary-side current detector 32, and the product of the two is calculated by the multiplier 41a, and a power signal 62 indicating the power generated by the solar cell 1 is generated. The power level of the power signal 62 is adjusted through the signal amplifier 45a and becomes a signal corresponding to the power generated by the solar cell 1.

The track hold 493 outputs the comparator output 6
While the value of the comparator output 64b changes from H to L while the value 4b continues to take the value of L, the value of the output of the signal amplifier 45a is held.

The comparator 44a outputs a value of H or L according to the magnitude of the output value of the signal amplifier 45a and the output value of the track hold 493, and the signal is compared by the D-flip-flop 51. When the value of the output 64b changes from L to H, it is sampled and held, and output as a command value amplitude change code signal 65.

Therefore, the power generated by the solar cell 1 when the value of the comparator output 64b changes from L to H is generated by the solar cell 1 when the value of the comparator output 64b changes from H to L. When it is larger than the power, the command value amplitude change code signal 65 takes a value of H, and when it is smaller, it takes a value of L.

The absolute value circuit 495 outputs the value of the absolute value of the input signal.
5 outputs a voltage about 0.7 times the positive peak value of the output. Since the output current of the inverter 23 is substantially proportional to the voltage of the AC power supply load 24, when the output power of the inverter 23 crosses the average value in the direction from small to large,
When the value of the comparator output 64b changes from L to H and crosses in the direction from large to small, it changes from H to L.

It is assumed that the capacity of the smoothing capacitor 21 is large to some extent, and the width of the voltage generated by the solar cell 1 that fluctuates periodically is small. Then, the waveform of the pulsating voltage generated by the solar cell 1 due to the operation of the smoothing capacitor 21 is as follows.
The output power of the inverter 23 is delayed by about 90 degrees with respect to the inverted power waveform. Therefore, near the time when the output power of the inverter 23 crosses the average value in the direction from small to large, the voltage generated by the solar cell 1 has a positive peak with respect to time, and the output power of the inverter 23 is The voltage generated by the solar cell 1 has a negative peak with respect to time around the time when the average value crosses from the large value to the small value.

When the voltage generated by the solar cell 1 periodically fluctuates around a voltage that is higher than the voltage at which the electric power generated by the solar cell 1 is maximized to a certain extent, the voltage generated by the solar cell 1 The power generated by the solar cell 1 at the time when the positive peak occurs with respect to time is higher than the power generated by the solar cell 1 at the time when the voltage generated by the solar cell 1 generates a negative peak with respect to time. Become smaller.

Conversely, when the voltage generated by the solar cell 1 periodically fluctuates around a voltage that is at least somewhat lower than the voltage at which the power generated by the solar cell 1 is maximized, the voltage generated by the solar cell 1 The power generated by the solar cell 1 at the time when a positive peak with respect to time is generated is higher than the power generated by the solar cell 1 at the time when the voltage generated by the solar cell 1 generates a negative peak with respect to time. Also increases.

Therefore, when the voltage generated by solar cell 1 fluctuates in a sinusoidal manner around a voltage that is at least somewhat higher than the voltage at which the power generated by solar cell 1 is maximized, the command value change code signal 65 has the value of H.
Then, the command value change code signal 65 is converted into a signal having a positive value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66 output from the integrator 43 rises. As a result, the average power converted by the inverter 23 increases, so that the average input current of the inverter 23 increases, and the average current generated by the solar cell 1 increases. Then, when the average voltage generated by the solar cell 1 decreases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to the voltage at which the power generated by the solar cell 1 is maximized.

On the contrary, when the voltage generated by the solar cell 1 fluctuates in a sinusoidal manner around a voltage that is lower than the voltage at which the power generated by the solar cell 1 becomes maximum to a certain extent, the command value change code The signal 65 has the value of L. Then, the command value change code signal 65 is converted into a signal having a negative value by the signal converter 46, and is then integrated by the integrator 43. The value of the command value amplitude signal 66 output from the integrator 43 decreases, As a result, the average power converted by the inverter 23 decreases, so that the average input current of the inverter 23 decreases, and the average current generated by the solar cell 1 decreases. Then, as the average voltage generated by the solar cell 1 increases, the voltage generated by the solar cell 1 periodically fluctuates around a value close to a voltage at which the power generated by the solar cell 1 is maximized.

In the fifth embodiment, the inverter system is controlled such that the voltage generated by the solar cell 1 fluctuates around a value close to the voltage at which the power generated by the solar cell 1 becomes maximum. From the voltage and current generated by the solar cell 1, the average output power of the corresponding inverter 23 is estimated in consideration of the conversion loss and the like in the inverter 23, and the inverter system is controlled so as to maximize the average output power of the inverter 23. May be.

In the fifth embodiment, the inverter 23
Of the output power of the inverter 23 that compares the value of the power generated by the solar cell 1 in the phase where the waveform of the output power of FIG. The two phases need only be shifted by about 180 degrees, and are not limited to the phases that intersect the average value.

In the fifth embodiment, the inverter 23
Is detected from the voltage of the AC power supply load 24, the timing at which the waveform of the output power of the inverter 23 reaches a specific phase is detected.
The timing at which the output power waveform reaches a specific phase may be detected.

Further, using the timing of zero crossing of the voltage of the AC power supply load 24, the output current of the inverter 23, or the output voltage and the output current of the inverter 23, the waveform of the output power of the inverter 23 has two specific phases. May be estimated and used.

Further, a signal from which the DC component is removed is generated for an amount determined by the voltage of the AC power supply load 24, the output current of the inverter 23, or the output voltage and the output current of the inverter 23, and the signal has a value. The timing at which the waveform of the output power of the inverter 23 reaches two specific phases may be generated by using the timing that intersects the value.

In the fifth embodiment, the inverter 23
Has been performed by controlling the amplitude of the current output by the inverter 23, but may be performed by controlling the amplitude of the voltage output by the inverter 23, or by controlling the amplitude of the voltage output by the inverter 23. This may be performed by controlling the amplitude.

[0119]

As described above, by using the present invention, an AC output solar cell power generation system having a maximum power point tracking function can be configured without using a DC / DC converter, so that a highly efficient AC output solar cell can be constructed. A power generation system can be realized.

Further, by using the present invention, in an AC output solar cell power generation system having a maximum power point tracking function, the maximum power point search is performed using a simple analog circuit and a digital circuit without using a microcomputer or the like. Since it can be realized, the cost of the system can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a signal waveform according to the first embodiment of the present invention.

FIG. 3 is a block diagram of a second embodiment of the present invention.

FIG. 4 is a signal waveform according to a second embodiment of the present invention.

FIG. 5 is a block diagram of a third embodiment of the present invention.

FIG. 6 shows a signal waveform according to a third embodiment of the present invention.

FIG. 7 is a block diagram of a fourth embodiment of the present invention.

FIG. 8 shows a signal waveform according to a fourth embodiment of the present invention.

FIG. 9 is a block diagram of a fifth embodiment of the present invention.

FIG. 10 shows a signal waveform according to a fifth embodiment of the present invention.

FIG. 11 is a block diagram of a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Solar cell 21 ... Smoothing capacitor 22 ... DC / DC converter 23 ... Inverter 24 ... AC power supply load 31 ... Primary voltage detector 32 ... ··· Primary current detector 33 ··· AC voltage detector 34 ··· AC current detector 41a and 41b ··· Multipliers 42a and 42b ··· Differentiator 43 ··· ..Integrators 44a, 44b comparators 45a, 45b, 45c signal amplifiers 46 signal converters 48 reference voltages 491a, 491b sample hold 492a 492b: peak detector 493: track hold 494: DC cutoff filter 495: absolute value circuit 51: D-flip-flop 52: exclusive OR gate 61 ・··· AC side voltage signal 62 ··· Power signal 63 ··· Power differential signal 64a, 64b ··· Comparator output 65 ··· Command value amplitude change sign signal 66 ··· Command value amplitude Signal 67 Command value signal 68 Primary voltage signal 691a, 691b Sample hold output 692 Track hold output 693 AC supply power 694 · Inverter control signal 70 ··· Microcomputer unit 71a, 71b ··· A / D converter 72 ··· PWM signal generator 73 ···· Current controller

Claims (5)

[Claims] In an inverter system for inputting DC power and outputting AC power, an inverter for converting DC to AC, a unit for detecting an amount of power supplied to the inverter system, and an inverter for the inverter system. Means for detecting an input state quantity which is an input voltage or current or an amount related to the voltage and current, and an electric power supplied to the inverter system at a time when the input state quantity has positive and negative peaks with respect to time. Means for comparing respective values of such quantities, and means for controlling operating conditions of the inverter, the power supplied to the inverter system when the input state quantity has positive and negative peaks with respect to time. By adjusting the operating conditions of the inverter so that the respective values of the quantities according to Maximum power operating inverter system characterized by bringing the power taken from the power source comprising a stem of the input to the maximum value. 2. An inverter system for inputting DC power and outputting AC power, wherein an inverter for converting DC to AC and means for detecting a sign of a time differential value of an amount of power supplied to the inverter system. And means for detecting the sign of the value of the time derivative of the input state quantity, which is the voltage or current of the input to the inverter system or the quantity related to the voltage and current, and means for controlling the operating conditions of the inverter, Or the time when the value of the time derivative of the input state quantity is positive, the time when the value of the time derivative of the input state quantity is negative, or the time when the value of the time derivative of the quantity related to the power is positive, or At the time when the value of the time derivative of the power-related quantity is negative, the exclusive OR of the sign of the time derivative of the power-related quantity and the sign of the time derivative of the input state quantity is obtained. Maximum power operating inverter system by a value which varies the operating conditions of the inverter, as a result, characterized in that close to the maximum power taken out from the power source as an input of the inverter system. 3. An inverter system for inputting DC power and outputting AC power, wherein an inverter for converting DC to AC and an amount related to a time derivative of an amount of power supplied to the inverter system are detected. Means, and means for detecting an amount related to the value of the time derivative at a time when an input state quantity, which is a voltage or current of the input to the inverter system or an amount related to the voltage and current, crosses a value close to the average value, and Means for controlling operating conditions of the inverter, wherein the input state quantity and the input state quantity at the time when the input state quantity crosses a value close to the average value and the input state quantity become the average value. The operating conditions of the inverter fluctuate in the direction crossing the near value, and as a result, the power taken from the power source which is the input of the inverter system approaches the maximum value. Maximum power operating inverter system according to claim Rukoto. 4. An inverter system for inputting DC power and outputting AC power, wherein the inverter converts DC to AC, and the power output from the inverter system has a positive or negative or positive and negative peak with respect to time. Means for detecting an amount related to the value of the time derivative of the amount of power supplied to the inverter system at a given time, and means for controlling operating conditions of the inverter. Varying the operating condition of the inverter by an amount related to the value of the time derivative of the amount of power supplied to the inverter system at a time having a positive or negative or positive and negative peak,
As a result, the maximum power operation inverter system characterized in that the power taken from the power supply which is the input to the inverter system approaches the maximum value. 5. An inverter system for inputting DC power and outputting AC power, wherein the inverter converts DC to AC and means for detecting the timing at which the waveform of the power output by the inverter system reaches two specific phases. And means for detecting an amount related to a difference between respective amounts of power supplied to the inverter system at a time when a waveform of power output from the inverter system reaches the two specific phases, and an operation of the inverter. Means for controlling the condition, and the amount of power supplied to the inverter system at the time when the waveform of the power output by the inverter system reaches the two specific phases is determined by the amount of the power supplied to the inverter system. Fluctuates operating conditions and consequently takes power from the power supply Maximum power operating inverter system, characterized in that close to be power to the maximum value.