JPS6327725B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a control device for a conversion device using a solar cell as a power source.

(b) Prior art and problems to be solved by the present invention Figure 6 shows an example of the configuration of the main circuit of a solar pump system that has been proposed so far.
is a solar cell, 2 is a diode, 3 is a capacitor,
Reference numeral 4 indicates an inverter as a converter, and 5 indicates a load consisting of an induction motor 6 and a pump 7 connected thereto. It should be noted that a conventional battery is shown for the purpose of diagrammatically illustrating that the part consisting of the solar cell 1, the diode 2 and the capacitor 3 operates as a conventional battery, for example a lead or alkaline battery. Although not shown in detail in FIG. 6, the inverter is, for example, a variable frequency control inverter whose output can be changed by changing its operating frequency. In order to maintain the output within a predetermined range, the output is divided into a battery voltage setting value given from a battery voltage setting device (not shown in Figure 6) and a battery voltage detection value from a battery voltage detector (not shown). The frequency is controlled according to the difference between

As described above, an energy conversion system consisting of a solar cell, a static power conversion device such as an inverter, and a load connected thereto has been proposed. In such a system, the output of the solar cell changes depending on the amount of sunlight and changes in the cell temperature, and efficient use of solar energy cannot be achieved unless the conversion device is appropriately controlled.

An object of the present invention is to provide a control device that enables efficient use of solar energy in the energy conversion system as described above even when there is a change in the amount of sunlight or a change in battery temperature.

(c) Principles and means for solving the problems Below, we will take as an example a case where the converter is an inverter and the load is an AC motor and a pump connected to it, that is, the case where the present invention is applied to a so-called solar pump system. Let me explain.

First, the characteristics of solar cells will be explained as a basis.

Figure 1 shows the characteristics of the output voltage (V) versus output current (A) of the solar cell when the amount of sunlight Ep is taken as a parameter under the condition of temperature Ta = 25°C.
The figure shows the amount of sunlight Ep under the condition of temperature Ta = 25℃
The characteristics of the output voltage (V) versus the output power (W) of the solar cell are shown when the parameter is taken as a parameter. In addition, in Fig. 1, IS1 to IS6 indicate short circuit current values,
VO1 to VO4 indicate voltage values when the output is open.

As is clear from Figure 2, in order to always obtain the maximum output at that point in time according to changes in the amount of sunlight,
The output of an inverter (generally speaking, a converter) and a load connected to the solar cell may be controlled so as to maintain the battery output voltage within a predetermined range indicated by V1 and V2.

Figure 3 shows the characteristics of the output voltage (V) vs. output current of the solar cell when the solar cell temperature Tc is taken as a parameter under the condition of sunlight amount Ep = 100 mV/ ^cm2 , and Figure 4 shows the characteristics of the output voltage (V) versus output current of the solar cell under the condition of sunlight amount Ep = 100 mV/cm2. 2 shows the characteristics of the output voltage (V) versus output power (W) of the solar cell when the solar cell temperature Tc is taken as a parameter under the condition of = 100 mV/cm ² . Note that the dashed-dotted line in FIG. 4 is a line connecting the maximum output points of the solar cells. As is clear from these drawings, simply controlling the output voltage of the solar cell within a predetermined range as described above cannot cope with power changes due to changes in battery temperature, resulting in significant output control errors and system failure. This will reduce the overall efficiency.

Therefore, in order to understand how the output power characteristics change due to changes in the solar cell temperature, the characteristics in FIG. 4 are rewritten to the characteristics at the maximum output point corresponding to the battery temperature, as shown in FIG. In addition, Tc=
25℃ indicates the standard value.

From FIG. 5, it can be seen that both the output power Pout and the output voltage Vout at the maximum output point decrease linearly as the solar cell temperature increases.

Therefore, in order to perform output control that appropriately responds to changes in the amount of sunlight and solar cell temperature, which greatly affect the output power of solar cells, it is necessary to create a control loop that maintains the output voltage of solar cells within a predetermined range. What is necessary is to correct the battery voltage command value by taking into account the temperature change of the solar cell. Taking this into consideration, the present invention provides a temperature sensor that is directly connected to the solar cell with silicone putty, etc., and outputs the output of this solar cell temperature sensor from the voltage setting value given from the battery voltage setting device as the battery voltage command value. The value obtained by subtracting the value is used.

(D) Embodiment FIG. 7 is a block circuit diagram of an embodiment of the present invention, in which 8 is a temperature sensor, 9 is an amplifier having an amplifier section A and three resistors, 10 is a battery voltage setting device, and 11 is a 12 is an addition point, 13 is a battery voltage regulator, and 14 is an inverter control unit consisting of a voltage-frequency converter 15, a motor voltage command unit 16, and a pulse distribution and shaping circuit 17. Component 12~
17 is a part that controls the output voltage of the solar cell 1 to be kept within a predetermined range, as described above with reference to FIG. The part according to the present invention is the part where components 8, 9, and 11 are added to the part that was supplied to point 12.

Next, the operation of the circuit shown in FIG. 7 will be explained.

First, the battery voltage is set according to the battery characteristics shown in FIG. adder 11
and is added to the set voltage value from the battery voltage setter 10. As a result, the output of this adder 11, which is corrected depending on the solar cell temperature according to the characteristics of the solar cell voltage (Vout) at the maximum output point in FIG. It is compared with the detected value. The output of the battery voltage regulator 13 controls the output of the inverter in a manner well known for inverter devices of this type. For example, when the output voltage of the solar cell is small, if the pump generates the maximum output at the maximum rotation speed, the battery voltage detection value will decrease, and the output of the voltage regulator 13 will decrease in the direction of lowering the output frequency of the inverter. As a result, the output voltage changes in the direction of decreasing the output voltage. Therefore, the output of the pump decreases, the detected value of the battery voltage increases, and a stable state is reached.

Although the present invention has been described above as applied to a solar pump system in which the conversion device is a variable frequency control inverter and the load is an induction motor and a pump, the present invention is not limited thereto. The converter can be any converter that operates with variable output, and the load can be any converter that operates with an output value that corresponds to the output value of the converter.

(e) Effects As explained above, the present invention controls the output of the load by correcting the solar cell voltage command value given to the battery voltage regulator by decreasing or increasing it in accordance with the increase or decrease in the solar cell temperature. Since the system is configured to do this, even if there is a change in the ambient conditions, the battery power is always operated at the maximum value. The scope of application of the present invention includes, in addition to the above-mentioned solar pump system,
This includes all systems in which loads such as fans, pumps, and blowers are connected via converters, whether direct current or alternating current.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the output voltage vs. output current characteristics of a solar cell with the amount of sunlight as a parameter. Figure 2 is a diagram showing the output voltage vs. output power characteristic of a solar cell with the amount of sunlight as a parameter. Figure 4 shows the output voltage vs. output current characteristics of a solar cell with solar cell temperature as a parameter. Figure 4 shows the output voltage vs. output power characteristic of a solar cell with solar cell temperature as a parameter. The figure shows the characteristics of the temperature of the solar cell versus the power and voltage at the maximum output point of the temperature, Figure 6 shows an example of the configuration of the main circuit of a solar pump system, and Figure 7 shows one implementation of the present invention. It is a figure which shows an example. 1: Solar cell, 4: Inverter, 5: Load,
8: Solar cell temperature sensor, 10: Battery voltage setter, 11: Adder, 12: Addition point, 13: Battery voltage regulator, 14: Inverter control unit, 15: Voltage-frequency converter, 16: Motor voltage command vessel, 1
7: Pulse distribution, shaping circuit.

Claims (1)

[Scope of Claims] 1. A solar cell that includes a solar cell, a conversion device driven by the solar cell, and a load supplied with power from the conversion device, and provides the maximum possible output to the load each time regardless of changes in the amount of sunlight. a setting means for giving a predetermined command value to the solar cell voltage so that the voltage is supplied to the solar cell; and controlling the conversion device so that the detected solar cell voltage matches the command value given by the setting means. In an energy conversion system equipped with an adjustment means, a solar cell temperature sensor is provided, and the command value given by the setting means is set so as to decrease the command value as the temperature rises in accordance with the output value of the sensor. 1. A control device for a converter driven by a solar cell, characterized in that the temperature-dependent shift in the maximum output point is compensated for by changing the temperature. 2. In the control device according to claim 1, the converter is driven by a solar cell, characterized in that it is comprised of a variable frequency control inverter whose output can be changed by changing its operating frequency. Control device for converter.