JPH02133811A - Photovoltaic power generating device - Google Patents

Abstract

PURPOSE:To keep the stable operation of a power converting part even though the optimum working voltage is changed with the secular change, etc., by changing the protection setting signal based on the voltage reference signal set at a level approximate to the optimum working voltage of a solar battery. CONSTITUTION:A voltage reference signal 4 of a voltage reference setter 3 and a protection reference signal 15 of a protection reference setter 14 are applied to a multiplier 16 for production of a protection setting signal 9. The signal 4 is set at a level approximate to the optimum working voltage of a solar battery 1 which is set when the battery 1 is newly added. When the output characteristics of the battery 1 change due to the secular change of the battery 1 and its optimum working voltage changes, the signal 4 is set again at a level close to the optimum working voltage according to the voltage change. Thus the operation of a power converting part 2 is kept without causing any interference between the input voltage to be applied to the part 2 and the signal 9 and in a state where the output voltage of the battery 1 is kept at its optimum working voltage.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention uses solar cells as a power source, converts DC power from the solar cells into AC power, and supplies this to the power system and load. Regarding solar power generation equipment.

(Prior Art) Recently, solar power generation devices have been attracting attention as an independent power source in remote areas.

FIG. 4 shows an example of the configuration of this type of conventional solar power generation device. In the figure, 1 is a solar cell that converts solar energy into electricity and generates it as DC power, 2 is a power conversion section that converts the DC power from the solar cell 1 into AC power, and 3 is the DC voltage of the power conversion section 2. A voltage reference setting device 6 is used to compare the voltage reference signal 4 from the voltage reference setting device 3 and the input voltage detection signal 5 of the power converter 2 to output a DC voltage setting signal 7. 8 is a protection level setting device 1 for setting the protection level of the power converter 2;
0 is a detection circuit that outputs a protection detection signal 11 based on the protection setting signal 9 of the protection level setter 8 and the input voltage detection signal 5 of the power converter 2; 12 is the DC voltage setting signal 7 from the comparator 6 and the detection circuit 10; This is a control circuit that receives a protection detection signal 11 from the power converter 2 and outputs a control signal 13 to the power converter 2.

As such a solar power generation device, the patent application No. 63-06
As disclosed in the specification of No. 8118, the value of the voltage reference signal 4 is set near the optimum operation of the solar cell 1 in order to efficiently utilize the output power of the solar cell 1, or as disclosed in Japanese Patent Application No. 61-224520. As disclosed in the specification, a device is known in which an undervoltage setting value and an overvoltage setting value are respectively set as the protection setting signal 9 for the purpose of protecting the power converter 2 from an accident state such as a cable short circuit. There is.

(Problem B to be solved by the invention) By the way, the output characteristics of the solar cells used in such solar power generation devices when newly installed are shown in Fig. 2 (a), but due to deterioration over time, the output characteristics change as shown in Fig. 2 (b). It is known that there is a decrease as shown in In this case, as the output characteristics change, the optimal operating voltage of the solar cell also changes from V op1 when newly installed to V op2 when aged, so in the device shown in FIG. The input voltage detection signal 5 of the power converter 2 is lowered by lowering the voltage reference signal 4 of
I am trying to change it from 1 to V op2.

However, in this case, if the undervoltage setting value is set to VLJ1% overvoltage setting value is set to VOI by the protection setting signal 9 of the protection level setting device 8 as shown in FIG. Voltage reference signal 4 of device 3
The input voltage detection signal V op of the power converter 2 after lowering
2 may become smaller than the undervoltage set value Vul, and for this reason, even though the output voltage of the solar cell has not decreased due to an abnormality, it is determined that an abnormality has occurred and the power conversion unit 2 is forced to operate. Sometimes I had to stop it.

The present invention has been made in view of the above circumstances, and provides a solar power generation device that can maintain stable operation at the power conversion unit even if the optimal operating voltage of the solar cell changes due to aging or other factors. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an apparatus for converting the output of a solar cell that converts solar energy into direct current power into alternating current power using a power conversion section and outputting the alternating current power. A DC voltage setting signal obtained from a voltage reference signal set near the optimum operating voltage and an input voltage detection signal of the power converter, a protection setting signal set based on the voltage reference signal, and an input voltage of the power converter. The power conversion section is controlled by a protection detection signal obtained from the detection signal.

(Function) As a result, the protection setting signal can be changed and set based on the voltage reference signal that is always set around the optimal operating voltage of the solar cell, so even if the optimal operating voltage changes due to aging of the solar cell, The input voltage to the power converter does not interfere with the protection setting signal, and the power converter can maintain operation while keeping the output voltage of the solar cell at the optimum operating voltage.

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

FIG. 1 shows an example of the configuration of the same embodiment, and the same parts as in FIG. 4 are denoted by the same reference numerals.

In the figure, 1 is a solar cell that converts solar energy into electricity and generates it as DC power, 2 is a power conversion section that converts the DC power from the solar cell 1 into AC power, and 3 is the DC voltage of the power conversion section 2. 6 is a voltage reference signal 4 from the voltage reference setter 3;
and a comparator that compares the input voltage detection signal 5 to the power conversion unit 2 and outputs a DC voltage setting signal 7; 14 is a protection standard setting device that outputs a protection standard signal 15 that is set to a predetermined value; 16 is a A multiplier that multiplies the voltage reference signal 4 of the voltage reference setter 3 by the protection reference signal 15 of the protection reference setter 14 and outputs the protection setting signal 9; A detection circuit 12 outputs a protection detection signal 11 based on the input voltage detection signal 5 of 2, and a detection circuit 12 receives the DC voltage setting signal 7 from the comparator 6 and the protection detection signal 11 from the detection circuit 10 to control the power converter 2. This is a control circuit that outputs a signal 13.

Here, the protection standard setting device 14 is configured such that, for example, in FIG. 2, the relationship between the undervoltage setting value Vul and the overvoltage setting value VOI with respect to the optimal operating voltage Vopl at the time of new installation is Vopl Xo, 8-Vul, and Voplx, respectively. iJ
-V 01, the protection reference signal 15 is set to 8 and 1
．． It is assumed that the value is set to 2 in advance.

Next, the operation of the embodiment configured as described above will be explained.

Now, when DC output is applied from the solar cell 1 to the power converter 2, it is converted into AC power and output. In this case, the voltage reference signal 4 of the voltage reference setter 3 is as shown in FIG. 2(a).
The voltage reference signal 4 and the input voltage detection signal 5 of the power converter 2 are compared by a comparator 6, and the comparison result is used as the DC voltage setting. It is given to the control circuit 12 as a signal 7, and the output of the power converter 2 is controlled.

At the same time, the voltage reference signal 4 of the voltage reference setter 3 and the protection reference signal 15 of the protection reference setter 14 are applied to the multiplier 1.
6 and a protection setting signal 9 is generated. in this case,
The protection setting signal 9 obtained from the multiplier 16 is set to the undervoltage setting value Vul (V□pi X018) and the overvoltage setting value VOI (Vopl X 1.2).

If the input voltage detection signal 5 of the power converter 2 fluctuates in this state for some reason and exceeds the undervoltage setting value Vul or overvoltage setting value VOI, the detection circuit 10 generates a protection detection signal 11 to that effect. given to the control circuit 12;
The operation of the power converter 2 is now controlled to stop.

By the way, when the output characteristics of the solar cell 1 change as shown in FIG. 2(b) due to aging, the optimum operating voltage V op2 also changes accordingly. Then,
The voltage reference signal 4 of the voltage reference setter 3 is also reset to near the optimal operating voltage V op2 at this time, so the protection setting signal 9 generated in this state is the same as the voltage reference signal 4 of the voltage reference setter 3. and the protection reference signal 15 of the protection reference setter 14
From the multiplication result, the undervoltage setting value Vu2 is (Vop2 x
o, 8) and the overvoltage setting value VO2 is (Vop2
l, 2), respectively. This means that solar cell 1
Even if the optimal operating voltage changes to V op2 due to aging, the undervoltage set value Vu2 and overvoltage set value VO2 are reset accordingly, so that the optimal operating voltage of the solar cell 1 that was conventionally The input voltage detection signal 5 of the corresponding power changing unit 2 can be completely prevented from interfering with the protection setting signal, and a situation where the operation of the power converter 2 is stopped by mistake can be reliably avoided.

By the way, if the optimal operating voltage changes due to aging of the solar cell, it is actually necessary to confirm this by measuring the output characteristics of the solar cell in advance and then set a new optimal operating voltage by replacing the voltage reference signal. However, it is nearly impossible to constantly monitor the output characteristics of solar cells in this way, especially when they are installed in unmanned facilities or private residences. Therefore, we adopted a maximum power follow-up control circuit to control the power conversion unit, and by using the average value over a certain period of time of the voltage reference value output by this maximum power follow-up control circuit as the voltage setting signal, the output characteristics of the solar cell are automatically adjusted. The protection setting signal may be changed in response to the deterioration of the protection setting signal.

FIG. 3 shows an example of a configuration for realizing such an idea, and the same parts as in FIG. 1 are designated with the same reference numerals. 17 is a maximum power follow-up control circuit that outputs a voltage reference value 19 that maximizes the DC power input to the power converter 2 from the input current detection signal 18 and input voltage detection signal 5 of the power converter 2; 20 is a maximum power follow-up control circuit; This is a sample hold circuit that outputs a voltage reference signal 21 as an average value of a voltage reference value 19 over a certain period of time. In this way, when the solar cell 1 deteriorates over time and its output characteristics deteriorate, the average value for a certain period of time is determined from the voltage reference value 19 output by the maximum power tracking control circuit 17 via the sample and hold circuit 20. Since it is output as the setting signal 21, the protection setting signal 9 is automatically set to the optimum value.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist.

For example, in the above embodiment, as a protection setting signal, an undervoltage setting value and an overvoltage setting value are set corresponding to the voltage reference signal, but one of them, for example, only the undervoltage setting value is set to the voltage reference signal. Even if the settings are made in accordance with the signals, interference between the protection setting signal and the optimum operating voltage can be prevented.

[Effects of the Invention] According to the present invention, it is possible to change and set the protection setting signal in accordance with the value of the voltage reference signal that is set near the optimal operating voltage of the solar cell, so that it is possible to change and set the protection setting signal in accordance with the value of the voltage reference signal that is set near the optimum operating voltage of the solar cell. Even when the optimum operating voltage changes, stable operation of the power converter can be maintained while keeping the output voltage of the solar cell at the optimum operating voltage without interfering with the protection setting signal.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a diagram showing the output characteristics of a solar cell, Fig. 3 is a block diagram showing another embodiment of the present invention, and Fig. 4 is a diagram showing a conventional solar cell. FIG. 1 is a configuration diagram showing an example of a photovoltaic device. DESCRIPTION OF SYMBOLS 1... Solar cell, 2... Power converter, 3... Voltage reference setter, 4... Voltage reference signal, 5... Input voltage detection signal, 6... Comparator, 7... ...DC voltage setting signal, 9...Protection setting signal, 10...Detection circuit, 11.
... protection detection signal, 12 ... control circuit, 13 ... control signal, 14 ... protection standard setter, 15 ... protection reference signal, 16 ... multiplier. Applicant's Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] A solar cell that converts solar energy into DC power, a power conversion unit that converts the output of the solar cell into AC power, a voltage reference signal set near the optimal operating voltage of the solar cell, and an input to the power conversion means. A control means for controlling the power converter using a DC voltage setting signal obtained from the voltage detection signal, a protection setting signal set based on the voltage reference signal, and a protection detection signal obtained from the input voltage detection signal of the power converter. A solar power generation device characterized by comprising: