JPH07334260A - Power generation controller for solar battery - Google Patents

Abstract

PURPOSE:To more efficiently extract power from a solar battery. CONSTITUTION:A searching operation for changing the output voltage or output current of a solar battery 8 so as to maximize the generated power of the solar battery 8 is intermittently performed at time intervals and during that time interval, an output voltage value or an output current value to maximize the generated power of the solar battery 8 is held. On the other hand, the change amount of the voltage or the current in the case of performing the searching operation is decided based on characteristic data showing the previously stored relation between the generated power and the voltage or the current. Therefore, the loss of power can be reduced in comparison with the conventional example to perform the searching operation with no interval, and the time required for the searching operation is shortened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation control device for efficiently extracting electric power from a solar cell used for solar power generation.

[0002]

2. Description of the Related Art In recent years, a system has been developed in which a distributed power source by solar power generation and a commercial power source are interconnected, and when the distributed power source cannot supply the power, the system side supplies the power. Has been done.

[0003]

The voltage-power characteristics of a solar cell used in such a system are generally as follows.
As shown in FIG. 8, the maximum power is generated at a certain voltage, but the voltage-power characteristics are greatly affected by the surrounding conditions such as the change in the amount of solar radiation (illuminance) due to the weather and the change in temperature. As indicated by the broken line, the voltage value (maximum power point) that generates the maximum power is deviated or the maximum power value is decreased.

Therefore, in the conventional system, in order to extract the maximum power from the solar cell, the voltage output from the solar cell is controlled by controlling the inverter circuit that converts the DC power from the solar cell into the AC power. , Fig. 9
By changing the voltage as shown in FIG. 9A, the operation of constantly searching for the voltage at which the electric power from the solar cell shown in FIG.

However, in the conventional control method in which the voltage is constantly changed to extract the maximum electric power as described above, in order to continuously change the voltage, the electric power to be extracted is as shown in FIG. 9B. However, there is a drawback that a loss is constantly generated below the maximum electric power MaXP, and the search operation requires a long time due to a shift of the maximum electric power point due to a relatively frequent change in illuminance. There is also a drawback that it causes power loss. Note that FIG. 9 shows a waveform in a state where there is no change in illuminance or temperature.

The present invention has been made in view of the above points, and an object of the present invention is to provide a power generation control device capable of more efficiently taking out electric power from a solar cell.

[0007]

In order to achieve the above-mentioned object, the present invention is constructed as follows.

That is, the present invention according to claim 1 is a power generation control device for controlling so that the generated power of the solar cell is maximized, and is based on the measured output voltage and output current of the solar cell. A calculating means for calculating the generated power of the solar cell; an output varying means for changing the output voltage or the output current of the solar cell; and a controlling the output varying means for changing the output voltage or the output current. And a control means for intermittently performing a search operation for searching for an output voltage value or an output current value at which the generated power calculated by the calculation means is maximum, at intervals of time, the control means comprising: During the interval, the output voltage or output current of the solar cell is held at the searched output voltage value or output current value.

According to a second aspect of the present invention, there is provided a power generation control device for controlling so that the generated power of the solar cell is maximized. By calculating means for calculating the generated power of the solar cell, output varying means for changing the output voltage or output current of the solar cell, and controlling the output varying means to change the output voltage or output current, And a control unit that performs a search operation to search for an output voltage value or an output current value at which the generated power calculated by the calculation unit is maximum, and the control unit has an output voltage according to the maximum generated power of the solar cell or And a storage unit that stores the output current data in advance, and the control unit reads the output voltage or the output current according to the generated power calculated by the calculation unit from the storage unit, Based on the output voltage or current readout of, and performs the search operation.

According to a third aspect of the present invention, there is provided a power generation control device for controlling so that the generated power of the solar cell is maximized. By calculating means for calculating the generated power of the solar cell, output varying means for changing the output voltage or output current of the solar cell, and controlling the output varying means to change the output voltage or output current, A search operation for searching for an output voltage value or an output current value at which the generated power calculated by the calculation means is maximum, and a control means for intermittently providing a time interval, and the control means,
The storage unit prestores data of the output voltage or output current according to the maximum generated power of the solar cell, and the control unit outputs the output voltage or output current according to the generated power calculated by the calculation unit. Based on the read output voltage or output current read from the storage unit, while performing the search operation, during the time interval, the output voltage or output current of the solar cell, the searched output voltage value or The output current value is held.

According to a fourth aspect of the present invention, in the first or third aspect of the present invention, the time interval is constant.

According to a fifth aspect of the present invention, in the first or third aspect of the present invention, when the amount of change in the generated power calculated by the calculating means exceeds the predetermined range during the time interval. Then, the search operation is started.

[0013]

According to the present invention as set forth in claim 1, the search operation for changing the output voltage or output current of the solar cell so that the generated power of the solar cell is maximized is intermittently performed at time intervals. , During that time interval, the output voltage value or output current value that maximizes the generated power of the solar cell is maintained, thus reducing the power loss that occurs because the search operation is constantly performed, as in the conventional example. You can do it.

According to the second aspect of the present invention, in order to deal with a change in illuminance and the like, data of the output voltage or output current corresponding to the maximum generated power of the solar cell is stored in advance, and the calculation means is used. The output voltage or output current according to the calculated generated power is read out, and the search operation is performed based on this, so even if the maximum power point of the solar cell shifts due to changes in illuminance that occur relatively frequently, depending on the shift Since the search operation is performed by changing the output voltage or the output current, the time required for the search operation is shortened as compared with the conventional example, and the power loss can be reduced.

According to the present invention of claim 3, claim 1
And the structure of claim 2 are provided, the structure of claim 1
The effect of the present invention and the effect of the present invention can be achieved together.

According to the present invention of claim 4, claim 1
Alternatively, in the present invention of 3, since the time interval of the search operation is constant, the constant time is set according to the weather of the place where the solar cell is installed and the surrounding conditions, so that the power loss is reduced. Can be reduced.

According to the present invention of claim 5, claim 1
Alternatively, in the present invention of claim 2, since the search operation is performed only when the amount of change in the generated power of the solar cell significantly changes, that is, when the generated power of the solar cell changes due to changes in temperature and illuminance, No power is lost due to the required search operation.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a system equipped with a power generation control device according to an embodiment of the present invention. In this embodiment, a system in which a distributed power source by solar power generation and a commercial power source are grid-connected It is applied to and explained.

In the figure, reference numeral 1 denotes a power system of a commercial power source, which is provided in a main power source 2 of a power station, a substation 3 for stepping down the power from the power station 2 and distributing the power, and a distribution line 4. The circuit breaker 5 and the pole transformer 6 for stepping down the supplied power and supplying it to each home are provided.

The distributed power source installed in each home comprises a solar cell 8 and an inverter device 10 incorporating an inverter circuit 9 for converting the DC power output from the solar cell 8 into AC power. In this embodiment, the inverter device 10 detects the opening of the circuit breaker 11 that disconnects the distributed power supply from the commercial power grid 1 and the breaker 5 of the commercial power grid 1 based on frequency fluctuations and voltage fluctuations. Then, a system interconnection protection device including an opening detection means 12 for opening the circuit breaker 11 is built in.

As another embodiment of the present invention, it goes without saying that the system interconnection protection device may be provided separately.

In such a system, when DC power is output from the solar cell 8, it is converted into AC power having a predetermined frequency by the inverter circuit 9 and the AC power is supplied to the domestic load 13, which is covered by this AC power. The power that cannot be supplied is supplied from the power grid 1 of the commercial power supply.

The inverter device 10 of this embodiment is constructed as follows so that electric power can be efficiently taken out from the solar cell 8.

That is, the inverter device 1 of this embodiment
0 is a calculating means 14 for calculating the generated power of the solar cell 8 based on the measured output voltage and output current of the solar cell 8, an output varying means 15 for changing the output voltage of the solar cell 8, and this output. The variable cell 15 is controlled to control the solar cell 8.
Control means 16 for intermittently performing a search operation to search for an output voltage value that maximizes the generated power calculated by the calculating means 14 by changing the output voltage of Is provided with a display means 17 for displaying a message such as when there is an abnormality.

The opening detecting means 12, the calculating means 14, the output varying means 15 and the controlling means 16 are constituted by a microcomputer 20.

The control means 16 of this embodiment does not constantly search the maximum power point by continuously changing the voltage output from the solar cell as in the conventional example, but performs the search operation at regular time intervals. In this case, the output voltage value already searched for is maintained during the time interval.

2 (A) and 2 (B) are waveform diagrams showing changes in voltage and power of the solar cell 8 according to this embodiment, corresponding to the conventional example of FIG.

As shown in FIG. 2, the control means 16
Controls the inverter circuit 9 via the output varying means 15 to change the output voltage of the solar cell 8 so that the voltage value at which the power output from the computing means 14 becomes maximum is 1
The voltage value searched for in the cycle S is held by the built-in timer for a fixed time T, for example, a period of 1 minute to several tens of seconds, and the searching operation is performed again.

As a result, in the prior art, power loss occurs as indicated by the slanted line L in order to constantly change the output voltage of the solar cell as shown in FIG. 9B, but in this embodiment, As shown in FIG. 2B, the loss is eliminated and the efficiency is increased.

The operation of power generation control as described above will be described in more detail with reference to the flowchart of FIG.

First, the direct current D which is the output of the solar cell 8
Take in I and DC voltage DV (step 101),
The calculation means 14 calculates the DC power amount DP (= DC current DI × DC voltage DV) (step 102) and performs initial setting for starting the search operation (step 103). In this initial setting, the voltage change amount dv = −m for changing the voltage.
[V] (m is an arbitrary value), the number of times the voltage is changed K =
0, maximum power amount MaxP = 0, voltage Max at maximum power
Let V = DV.

Next, the inverter circuit 9 is controlled so that the DC voltage output from the solar cell 8 becomes DV + dV (step 104). That is, the DC voltage is m
[V] Control to lower the value. The DC current DI and the DC voltage DV are fetched (step 105), the previous DC power amount DP0 = DP is set (step 106), and the DC power amount DP is calculated based on the DC current DI and the DC voltage DV fetched in step 105 ( Step 10
7).

Next, it is judged whether or not the calculated DC power amount DP is larger than the maximum power amount MaxP (step 108). When it is larger, the maximum power amount MaxP = DP.
In addition, the maximum power voltage MaxV = DV is set (step 109), and it is determined whether or not the previous DC power amount DP0 is larger than the current DC power amount DP (step 110). dV = -dV
That is, the direction of voltage change is reversed, and the number of voltage changes K = K + 1 (step 11).
1).

It is judged whether or not the number of voltage changes K = 2 (step 112). When K = 2 is not satisfied,
Returning to step 104, the same processing is performed, and when K = 2, the inverter circuit 9 is controlled so that the DC voltage becomes DV + dV (step 113), and the DC voltage DV is the voltage MaxV at the maximum power. It is judged whether or not it is larger than the above (step 114), and if it is larger, the process returns to step 113. In FIG. 2, the value of K is shown so that the correspondence with this flowchart is clear.

In this embodiment, the search operation is performed at a constant time interval (n seconds), but as another embodiment of the present invention, the calculating means 14 is not performed at a constant time interval. The search operation may be started when the amount of change in the generated electric power calculated in step 4 exceeds a predetermined range.

FIG. 4 is a flow chart for explaining the operation of such a configuration, and the same steps are designated by the same reference numerals and the description thereof will be omitted.

In this embodiment, when it is determined in step 114 that the DC voltage DV is not higher than the maximum power voltage MaxV, the previous DC power amount DP0 = DP is set instead of waiting for n seconds (step 11
6), the DC current DI and the DC voltage DV are fetched (step 117), and the DC power amount DP is calculated (step 1).
18), the previous DC power amount DP0 and the current DC power amount D
It is judged whether or not the absolute value of the difference from P is larger than a predetermined value n [W] (step 119), and when it becomes larger, the process returns to step 101 to restart the search operation, and becomes larger. If not, the process returns to step 117.

In this embodiment, the search operation is performed only when the amount of change in the generated power of the solar cell 8 changes significantly, that is, when the maximum power point of the solar cell 8 shifts due to changes in temperature and illuminance. Since this is done, power is not lost due to unnecessary search operations.

In this embodiment or the above-mentioned embodiment, when the change in the DC power amount exceeds the predetermined range or when the predetermined time has elapsed, step 1
However, as shown in the voltage-power characteristics of the solar cell in FIG. 5, when the illuminance is large and the generated power is large, as shown by the line A, Amount d of change in power due to change
Although P is large, when the illuminance is small and the generated power is low, the change amount dP of the power with respect to the voltage change is small as shown in the line B. Therefore, even when the generated power is too small, the search operation is performed. On the contrary, there is a possibility that the power generation efficiency is lowered due to useless operation.

Therefore, as another embodiment of the present invention, for example, in step 119 of the flowchart of FIG.
When the absolute value of the difference between the previous DC power amount DP0 and the current DC power amount DP becomes larger than a predetermined value n [W], the process returns to step 101 and the search operation is not immediately restarted, but the DC power is not restarted. It is determined whether or not the power DP is smaller than a predetermined relatively small value, and if it is smaller, it is considered that improvement in power generation efficiency cannot be expected even if the search operation is performed, and thus the search operation is not restarted and the process proceeds to step 117. You may return.

According to this embodiment, when the illuminance is small and the generated power is low, useless search operation is not performed, and the power generation efficiency is expected to be improved.

FIG. 7 is a flow chart for explaining the operation of still another embodiment of the present invention. In this embodiment, even when the maximum power point is largely deviated due to a change in illuminance, the deviation is dealt with. By performing the search operation, the time required for the search operation is shortened and the power loss is reduced.

The system of this embodiment is also the same as the embodiment of FIG. 1, but in this embodiment, the control means 16 stores in advance the data of the output voltage corresponding to the maximum generated power of the solar cell 8. A storage unit (ROM) is built in, and an output voltage corresponding to the generated power calculated by the calculation unit 14 is read from the storage unit, and based on the read output voltage,
A search operation is performed.

The voltage value at which the maximum power of the solar cell 8 is generated due to the change in illuminance that occurs relatively frequently, that is, the locus of the maximum power point shifts as shown by the line C in FIG. By storing the characteristic data in the storage unit in advance, when the power changes due to the change in illuminance, the voltage corresponding to the power is read and the voltage is changed so that the vicinity of the voltage can be searched. This shortens the time required for the search operation.

That is, in this embodiment, as shown in FIG. 7, the DC current DI and the DC voltage DV which are the outputs of the solar cell 8 are fetched (step 201), and the calculation means 14 calculates the DC power amount DP (= DC current). DI x DC voltage D
V) is calculated (step 202), and the voltage change amount dV = −n [V] (n is an arbitrary value) for changing the voltage is set (step 203), and the voltage correction amount VR is stored in the storage unit of the control means 16. Read out (step 204).

Next, the inverter circuit 9 is controlled so that the DC voltage output from the solar cell 8 becomes DV + dV + VR (step 205).

In this embodiment, as in each of the above-described embodiments, the voltage is not simply changed by dV, but the maximum power point is deviated based on the data of the storage unit according to the DC power amount at that time. On the other hand, the voltage change amount is corrected so that the voltage can be tracked more quickly.

Next, the DC current DI and the DC voltage DV are fetched (step 206), and the previous DC power amount DP0 is obtained.
= DP (step 207), the DC power amount DP is calculated based on the DC current DI and the DC voltage DV acquired in step 206 (step 208), and whether the previous DC power amount DP0 is larger than the current DC power amount. It is determined whether or not (step 209), and when it is not large, the process returns to step 204, and when it is large, the voltage change amount dV.
= -DV, that is, the direction in which the voltage is changed is reversed, and the process returns to step 204 (step 300).

The configuration of this embodiment may be combined with the configuration of each of the above embodiments.
That is, in each of the above-described embodiments, when the voltage is changed, the amount of change in the voltage may be corrected based on the data in the storage unit as in this embodiment.

Although the above embodiments have been described by applying to the system interconnection system of the distributed power source and the commercial power source, the present invention is not limited to such a system and can be applied to other solar power generations. Of course.

In each of the above-mentioned embodiments, the output voltage is changed, but it goes without saying that the output current may be changed.

[0053]

As described above, according to the present invention, the search operation for changing the generated power of the solar cell to the maximum,
It is performed intermittently with a time interval, and during that time interval,
Since the output voltage value or output current value that maximizes the generated power of the solar cell is maintained, it is possible to reduce the power loss that occurs as in the conventional example because the search operation is constantly performed.

Further, according to the present invention, data of the output voltage or output current corresponding to the maximum generated power of the solar cell is stored in advance, and the output voltage or output according to the generated power calculated by the calculating means is stored. Since the current is read and the search operation is performed based on this, even if the maximum power point of the solar cell shifts significantly due to changes in illuminance that occur relatively frequently, the search operation is performed according to that shift. Will be shortened compared to the conventional example, and power loss can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a system to which an embodiment of the present invention is applied.

FIG. 2 is a waveform diagram showing changes in voltage and power of the solar cell according to the embodiment of FIG.

FIG. 3 is a flowchart for explaining the operation of the embodiment of FIG.

FIG. 4 is a flowchart for explaining the operation of another embodiment of the present invention.

FIG. 5 is a voltage-power characteristic diagram of a solar cell.

FIG. 6 is a voltage-power characteristic diagram of a solar cell showing a locus of a maximum power point.

FIG. 7 is a flow chart for explaining the operation of still another embodiment of the present invention.

FIG. 8 is a voltage-power characteristic diagram of a solar cell.

FIG. 9 is a waveform diagram showing changes in voltage and power of a solar cell according to a conventional example.

[Explanation of symbols]

 8 solar cell 9 inverter circuit 10 inverter device 14 computing means 15 output varying means 16 control means

Claims (5)

[Claims] 1. A power generation control device for controlling so that the generated power of a solar cell is maximized, wherein the generated power of the solar cell is calculated based on the measured output voltage and output current of the solar cell. And a variable output means for changing the output voltage or the output current of the solar cell, and a power generation calculated by the calculating means by changing the output voltage or the output current by controlling the output variable means. The search operation for searching the output voltage value or the output current value at which the electric power becomes maximum is provided with a control unit that intermittently opens a time interval, and the control unit, during the time interval, the solar cell A power generation control device for a solar cell, which holds an output voltage or output current at a searched output voltage value or output current value. 2. A power generation control device for controlling so that the generated power of the solar cell is maximized, wherein the generated power of the solar cell is calculated based on the measured output voltage and output current of the solar cell. And a variable output means for changing the output voltage or the output current of the solar cell, and a power generation calculated by the calculating means by changing the output voltage or the output current by controlling the output variable means. And a control unit that performs a search operation to search for an output voltage value or an output current value that maximizes the electric power, and the control unit stores in advance data of the output voltage or the output current according to the maximum generated power of the solar cell. The control means reads out an output voltage or an output current according to the generated power calculated by the calculation means from the storage part, and outputs the read output voltage. Or on the basis of the output current, the power generation control device for a solar cell and performs the search operation. 3. A power generation control device for controlling the power generation of a solar cell to be maximum, wherein the power generation of the solar cell is calculated based on the measured output voltage and output current of the solar cell. And a variable output means for changing the output voltage or the output current of the solar cell, and a power generation calculated by the calculating means by changing the output voltage or the output current by controlling the output variable means. A search operation for searching for an output voltage value or an output current value at which the electric power becomes maximum, and a control means for intermittently providing a time interval, and the control means has an output according to the maximum generated power of the solar cell. The control unit has a storage unit in which data of voltage or output current is stored in advance, and the control unit reads out the output voltage or output current according to the generated power calculated by the calculation unit from the storage unit. Then, based on the read output voltage or output current, while performing the search operation, during the time interval, the output voltage or output current of the solar cell to the searched output voltage value or output current value. A power generation control device for a solar cell, which is held. 4. The power generation control device for a solar cell according to claim 1, wherein the time interval is constant. 5. The solar cell according to claim 1, wherein the search operation is started when the amount of change in the generated power calculated by the calculation means exceeds a predetermined range during the time interval. Power generation control device.