JPH07129264A - Solar power system - Google Patents

Abstract

PURPOSE:To obtain a solar battery system of simple constitution which is low in power consumption and has high efficiency by detecting the output voltage of a solar battery and the output current of an electric power converting means and detecting the operation point of the solar battery from the variation tendency of the output voltage and the variation tendency of the output current. CONSTITUTION:The solar battery 1 is connected to the electric power converting means 4 through a reverse current preventive diode 3 and the electric power generated by the solar battery 1 is converted by the electric power converting means 4 and then supplied to a storage battery 2. At this time, variations of the output voltage of the solar battery 1 and the output current of the electric power converting means are temporarily stored in an analog signal state, and comparators 12 and 13 decide the variation tendencies of the respective outputs; and the results are processed by an exclusive OR circuit XOR to decided the direction of the maximum output point of the solar battery, thereby supplying a command to the electric power converting means 4 so as to make the solar battery automatically track to the maximum output point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generation system for detecting the operating point of a solar cell so as to automatically track the maximum output point of the solar cell so that the maximum power can always be supplied stably. Regarding

[0002]

2. Description of the Related Art Conventionally, a control system as shown in FIG. 3 is known in order to obtain maximum power from a solar cell. In this system, the solar cell P feeds the power generated by the solar cell P to each of the independent load L and the other power supply system A through a power converter H such as a chopper or an inverter.

Here, a voltage detector DV, a current detector DI, and a control circuit C are provided between the solar cell P and the power converter H.
C is provided, the voltage detector DV detects the output voltage of the solar cell P, and the current detector DI detects the output current of the solar cell P. As a result, the control circuit CC causes the solar cell P to
Generated power (= detection voltage × detection current) is calculated, then the operating point of the solar cell P is slightly changed, and new generation power is calculated by the product of the detection voltage and the detection current obtained again, The operating point of the solar cell P is searched from the difference between these generated powers, and the output of the converter H is controlled so that the maximum power can be obtained from the solar cell P (JP-A-56).
-See the gazette of No. 91630).

However, the control circuit of such a system is equipped with, for example, a microprocessor, etc., and further, after the detected voltage and the detected current are digitized by using an A / D converter or the like, the arithmetic processing is performed. Because of the configuration, the control circuit becomes complicated. Further, since the power consumption increases due to the complexity of the control circuit and the efficiency does not increase particularly in a small-scale storage battery charging control system or the like, the control circuit cannot be applied to a small-scale system.

[0005]

[Object] Therefore, the present invention was devised in view of the problems of the above-described conventional system, and an object of the present invention is to provide a highly efficient solar power generation system with a simple circuit configuration and low power consumption. .

[0006]

In order to achieve the above object, the photovoltaic power generation system of the present invention is a photovoltaic power generation system in which the generated power of a solar cell is supplied to a load through a power conversion means. It is characterized in that the output voltage from the solar cell and the output current from the power conversion means are detected, and the operating point position of the solar cell is detected from the fluctuation tendency of the output voltage and the fluctuation tendency of the output current. .

Here, the load is not limited to ordinary electric appliances and the like, but can be applied to, for example, storage batteries, inverters, power supply systems and the like.

[0008]

According to the above-mentioned structure, the operating point position of the solar cell is determined from only the fluctuation tendency of the output voltage from the solar cell and the output current of the power conversion means without performing the calculation processing of the generated power of the solar cell as in the conventional case. Can be easily detected. For example, the fluctuation of the output voltage of the solar cell and the output current of the power conversion means is temporarily stored in an analog signal state, the fluctuation tendency of each output is determined by a comparator, and the result is determined by an exclusive logic OR circuit. By processing, the direction of the maximum output point of the solar cell can be determined, and a command can be given to the power conversion means to automatically track the solar cell to the maximum output point.

[0009]

EXAMPLE An example of the solar power generation system according to the present invention will be described in detail below. As shown in FIG. 1, the solar power generation system S is configured to efficiently charge a storage battery 2 which is a load of the solar cell 1, and the solar cell 1 converts power via a backflow prevention diode 3. It is connected to the means (DC / DC converter) 4, and the electric power generated from the solar cell 1 is converted into electric power by the electric power conversion means 4 and then supplied to the storage battery 2. At this time, the control circuit (operating point detection circuit) MC detects the operating point position of the solar cell 1 and issues a command to the power conversion means 4 so that the solar cell 1 operates at the optimum operating point.

The small resistance 5 provided between the power conversion means 4 and the storage battery 2 is a general one as a shunt resistor for current detection, and is a small resistance that hardly affects the storage battery 2. Has a value. At both ends of the minute resistor 5,
A voltage corresponding to the charging current generated by the solar cell 1 is generated.
The voltage dividing resistors 6 and 7 provided between the solar cell 1 and the power conversion means 4 are provided for the purpose of detecting the operating voltage of the solar cell 1.

Next, the control circuit MC will be described in detail. The operating voltage of the solar cell 1 is converted to an appropriate voltage by the voltage dividing resistors 6 and 7, and then buffered and amplified by the buffer amplifier 8. Further, the output current (charging current) from the power converting means 4 to the storage battery 2 is set to an appropriate value by the micro resistor 5 for current detection, and is amplified to an appropriate value by the buffer amplifier 9 in the same manner as the above operating voltage. It These voltage signal and current signal are temporarily held by each of the sample and hold circuits 10 and 11 in the next stage.

A sample and hold circuit 1 including an operational amplifier, an analog switch, a capacitor for voltage charging, etc.
A signal having a time difference based on the sampling period (Δt) determined by the sampling period signal generation circuit 14 is input to the differential inputs of the comparators 12 and 13 on the output sides of 0 and 11, respectively. (Δt)
Compare the previous value with the current value.

As a result, the respective output values of the comparators 12 and 13 show a tendency to change from that before the sampling period (Δt). For example, when the output voltage of the solar cell 1 is increasing, the output is 1, and when it is decreasing, the output is 0. To the negative input of each of the comparators 12 and 13,
The data before (Δt) is input to the sample fold circuit 11. On the other hand, the current data is directly input to the plus input. Therefore, if the output voltage of the solar cell 1 rises compared to before (Δt), the plus input side of the comparator 12 becomes high, and the output of the comparator 12 becomes 1 and drops on the contrary. If it is, the output of the comparator 12 becomes 0 because the minus side becomes higher.

When the output changes of the comparators 12 and 13 are examined together with the operating characteristics of the solar cell 1, a line L1 showing the voltage-current characteristics of the solar cell 1 is shown, for example, as shown in FIG. In the above, the line L2 showing the relationship between the output voltage of the solar cell 1 and the output current (charging current) of the power conversion means 4 is located above and below the intersection X1 with the line MP at which the solar cell 1 has the maximum output. Since it is similar to the voltage-power characteristics of the solar cell 1, the fluctuation tendency between the output voltage of the solar cell 1 and the output current of the power conversion means CL should be inverted with the intersection X2 between the line L2 and the line MP interposed. I understand. That is, there are four states after Δt from the state at a certain T time, and the output signals from the comparators CV and CA (the input signals of the exclusive OR logic circuit XOR at the next stage) in each state,
The output signal of the exclusive OR logic circuit XOR is as shown in Table 1.

[0015]

[Table 1]

As is clear from Table 1, when the output voltage tends to increase and the output current also tends to increase, or when the output voltage tends to decrease and the output current tends to decrease, that is, the exclusive OR logic circuit. When the output signal of XOR is 0, the output voltage (operating point) of the solar cell 1 is located on the left side of the line MP. Therefore, in such a case, the control circuit MC sets the command value to the power conversion means CL to a value higher than the current command value by ΔV.

On the other hand, when the output voltage tends to increase and the output current tends to decrease, or when the output voltage tends to decrease and the output current tends to increase, that is, the output signal of the exclusive OR logic circuit XOR becomes 1. In this case, the output voltage of the solar cell 1 is located on the right side of the line MP. Therefore, in such a case, the control circuit MC controls the power conversion means C.
The command value to L is set to a value lower than the current command value by ΔV.

As described above, when the above series of operations are repeated, the command value of the power conversion means CL gradually changes so as to reach the optimum operating point (line MP) of the solar cell 1. Then, the up and down movement of the output voltage ΔV is repeated near the line MP, and 2
The operating point of the solar cell PV moves within the range of ΔV. Therefore, it is possible to achieve the optimum operating point quickly and maintain the optimum operating point without setting or controlling the magnitude of ΔV appropriately.

In this embodiment, the fluctuations in the output voltage of the solar cell and the output current of the power conversion means are temporarily stored in an analog signal state, and the fluctuation tendency of each output is judged by a comparator. Is processed by an exclusive logic OR circuit to determine the direction of the maximum output point of the solar cell,
The system that gives a command to the power conversion means to automatically track the solar cell to the maximum output point has been described, but the output voltage from the solar cell and the output current from the power conversion means are detected at regular time intervals, and the output voltage A system that detects the operating point of the solar cell based on the variation tendency and the variation tendency of the output current may be used, and the system is not necessarily limited to the above aspect. Further, the load is not limited to the above-mentioned storage battery, but may be applied to an inverter or other power supply system, etc., and may be appropriately modified and implemented within the scope not departing from the gist of the present invention.

[0020]

As described in detail above, according to the solar power generation system of the present invention, it is not necessary to calculate the generated power of the solar cell as in the conventional case, and the output voltage of the solar cell and the power conversion means are simply used. Since the operating point of the solar cell is detected only from the output current of the solar cell, the configuration is extremely simple and the power consumption can be suppressed as much as possible. It can also be applied to systems and the like, and can supply almost 100% of the power generation of a solar cell to a load (especially a storage battery), and to provide an extremely excellent solar power generation system with significantly improved utilization efficiency compared to the past. it can.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a photovoltaic power generation system according to the present invention.

FIG. 2 is a graph showing the relationship between the current-voltage characteristics of the solar cell and the output current (charging current) of the voltage-power conversion means of the solar cell.

FIG. 3 is an overall configuration diagram showing a conventional photovoltaic power generation system.

[Explanation of symbols]

1 ... Solar cell 2 ... Storage battery 3 ... Backflow prevention diode 4 ... Power conversion means 5 ... Micro resistance 8,9 ... Buffer amplifier 10, 11 ... Sample hold circuit 12, 13 ... Comparator MC ... Control circuit (operating point detection circuit)

Claims (1)

[Claims] 1. A solar cell, power conversion means for converting generated power of the solar cell into a predetermined output and supplying it to a load, and issuing a command to the power conversion means so that the solar cell operates at an optimum operating point. A photovoltaic power generation system comprising a control means, wherein the control means detects an output voltage from the solar cell and an output current from the power conversion means, and a fluctuation tendency and an output current of the detected output voltage. A photovoltaic power generation system comprising an operating point detection circuit that detects an operating point position of the solar cell based on a fluctuation tendency.