JPS62126418A - Photovoltaic power generating device - Google Patents

Abstract

PURPOSE:To prevent an excess voltage protecting device from malfunction by applying voltage to the 2nd resistor during the stop of an inverter of the voltage applied to the inverter exceeds a prescribed value. CONSTITUTION:When the inverter 7 is started from its stopped state, the output voltage of a solar battery 1 is reduced in accordance with the increase of current and the voltage Vin applied to the inverter is also reduced. Since the excess voltage protecting circuit is not driven after starting the inverter 7, the time (t) is measured by a timer in a relay contact control device 8, and after the passage of the time (t), a relay 6 is closed to impress the output voltage Vop of the solar battery to the inverter 7 as it is. If the inverter 7 is stopped by any cause, the output voltage is boosted in accordance with the decrease of the output current and reached to its opened voltage Vmax. Since the relay contact control device 8 has opened the relay 6 immediately after receiving an operation stop signal from the inverter 7, the input voltage Vin of the inverter 7 is divided by resistors 4, 5 and set up to a voltage value to be applied to the resistor 5.

Description

[Detailed description of the invention] Regarding the location.

[Technical background of the invention and its problems] In general, solar cells have larger voltage fluctuations than alkaline or lead batteries, and their output changes significantly in response to changes in the solar radiation intensity or changes in the circumference of 111 IW degrees. In order to always operate at the maximum possible output, it is necessary to control the solar cell voltage or power according to changes in parameters such as solar radiation intensity and ambient temperature. The characteristics of this human IIi battery will be explained using FIG. 4. Fig. 4 shows the thick l! J! The characteristics of the output voltage (V) versus output current (A) and the output voltage (V) versus output power (W) of the battery are shown. As can be seen from FIG. 4, solar cells have a characteristic that as the output current increases, the output voltage decreases to zero. Conversely, there is a characteristic that as the output current decreases, the output voltage increases and finally reaches the open circuit voltage. This means that there are large voltage fluctuations in the solar cell. Therefore, in general, electric 1PlJ machines that drive pumps, fans, etc. require a large current when starting, so when driving a motor with a thick wattage battery, the capacity is considerably larger than the capacity of a thick meter battery required for steady operation. If the device is not equipped with solar cells, the problem remains that the equipment becomes larger and more expensive.

In order to solve the above problems, an inverter with AC-DC conversion function and frequency conversion function is interposed between the solar battery and the motor, so that the current at startup is almost the same as the current during steady operation. In this way, we are trying to make the device more compact.

As can be seen from the characteristics of output voltage (V) and output power (W) in Figure 4, which generally shows the characteristics of solar cells, the voltage value at which the maximum output power of a solar cell is 1q is almost constant, so this voltage Control the output voltage of the solar cell to the value. However, once the system stops and no current flows, and the solar cells are in the same state as if no load is connected to them, the output voltage of the solar cells rises to the open-circuit voltage, and compared to the voltage output during operation. There was a problem in that a voltage approximately 1.5 times higher than that of the inverter was applied, exceeding the voltage of the overvoltage protection level of the inverter, and the protection operation was activated. Furthermore, the open-circuit voltage of the solar cell is also affected by changes in ambient temperature, and even if the overvoltage protection operation does not operate at room temperature, the open-circuit voltage of the solar cell increases at low temperatures, causing problems.

Therefore, in order to prevent the overvoltage protection operation from operating even at open circuit voltage, it is necessary to increase the withstand voltage level of the main elements of the inverter, resulting in a problem that increases the cost of the device.

[Object of the Invention] The present invention provides a solar power generation device that can drive the overvoltage protection operation of the inverter without malfunctioning even when the solar cells are in a no-load state and the output voltage of the solar cells has reached the open-circuit voltage. The purpose is to provide

[Summary of the Invention] That is, the present invention provides a solar power generation device in which a solar cell is used as a power source and a motor is excited through an inverter to drive a load, in which the output voltage of the solar cell is controlled by first and second resistors. A switching device is connected between the terminals of the first resistor to open and close depending on the state of the inverter, and an inverter is connected between the terminals of the second resistor. or when the input voltage of the inverter exceeds a predetermined value, the switchgear is opened and the voltage divided by the first and second resistors and applied to the second resistor is supplied to the inverter. The feature is that malfunction of the overvoltage protection device can be prevented.

[Embodiment of the Invention] The present invention will be described below with reference to a first practical example in which a pump shown in FIG. 1 is used as a load. In the figure, reference numeral 1 denotes a solar cell, and at its output end, a first resistor 4 and a second resistor 5 are connected in series through a diode for backflow prevention, a capacitor 3 that absorbs ripples in the output voltage, and a first resistor 4 and a second resistor 5 are connected in series to reduce the output voltage. It divides the pressure. Furthermore, a relay 6 and an inverter 7, which are switching devices, are connected in parallel to the resistor 4 and the resistor 5, respectively.
The relay 6 receives commands to start/stop the inverter 7, etc.
Depending on the state, opening and closing are controlled by a relay contact control device 8 having a timer function. An electric motor Ia9 is connected to the AC output side of the inverter to drive a pump 10 as a load.

Next, the operation will be explained with reference to FIG. Now, assuming that the inverter 7 is stopped, the relay 6 is open, and the input voltage Vin of the inverter is the voltage applied to the resistor 5 by dividing the open circuit voltage V max of the solar cell 1 by the resistor 4 and the resistor 5. Approximately the same voltage is applied. In other words, the following relationship holds true.

V in = V max -1 and 1- (1)
R4+R5 Here, Vin is the voltage applied to the resistor 5 (input voltage of the inverter, V max is the open circuit voltage of the solar cell 1 (this open circuit voltage changes somewhat depending on the solar radiation intensity, but here v m
(represented by ax) R4 is the resistance value of the resistor 4, and R5 is the resistance value of the resistor 5.

The voltage Vin applied to the resistor 5 after voltage division is applied to the inverter 7
Since this is the voltage applied at the moment of activation, if it is set too low, it will be difficult to start. Accordingly, from the above equation (1), the ratio of the resistance values R4 and R5 is determined so that Vin≧VOD.

Also, since the resistor 5 forms a parallel circuit with the inverter 7 during steady operation, the resistance value R is set so that the current flowing here is sufficiently negligible compared to the current flowing through the inverter 7.
Determine 5.

When the inverter 7 starts operating from this state, the current that had previously flowed only through the resistor 4.5 will now flow through the inverter 7, so the output voltage of the solar battery will increase as the current increases, as shown in Figure 3. As shown in the figure, the input voltage V of the inverter decreases by moving in the direction of arrow 20.
in also decreases as shown in FIG. The inverter 7 detects the output voltage of the solar cell and controls the AC voltage and frequency so that this becomes the voltage value VOD that can obtain the maximum power,
Since operation is performed at maximum efficiency, the output voltage of the solar cell is reduced to VOD and held at this value. Therefore, since the overvoltage protection circuit will not operate after startup, this time t is measured by the timer of the relay contact system tlII device 11, and after the time has elapsed, the relay 6 is opened and the output voltage of the solar cell OP is directly transferred to the inverter. 7 and becomes the input voltage Vin.

After that, if the inverter 7 stops for some reason, the output current of the solar cell becomes almost zero, so the output voltage increases as shown in Figure 3 as the output current decreases, and finally the open circuit voltage v max is reached. At this time, the relay contact control I device 8 has already received the operation stop signal from the inverter 7 and immediately opens the relay 8, so the input voltage Vin of the inverter 7 is obtained by dividing V max by the resistor 8.9. This is the voltage value applied to .

As described above, according to the first embodiment of the present invention, when the output voltage of the solar cell reaches the open circuit voltage vmax, the voltage divided by the resistor 4.5 is set as the input voltage Vin of the inverter, and the output current from the solar cell is When the current output voltage drops to the voltage value Vop that can obtain the maximum power, it is configured so that it becomes the input voltage Vin of the inverter, so the overvoltage protection operation can be performed on the input voltage of the inverter without increasing the withstand voltage level of the main elements. The more you don't work, the more you can control the epidemic.

A second embodiment of the present invention will be described below with reference to FIG. In the figure, the same numbers as in FIG. 1 indicate the same or corresponding parts, and 11 is a voltage detection device that detects the input voltage of the inverter 7 and issues a command to open the relay 6 to the relay contact control device @8.

In this embodiment, the opening operation of the relay 6 is performed by detecting that the output voltage of the solar cell is higher than a predetermined value as in the first embodiment, but the opening operation of the relay 6 is performed by the input of the inverter 7. This is done by detecting voltage. Generally, when the input voltage of the inverter during steady operation is vop, and the open circuit voltage of the solar cell is vmax, the overvoltage protection voltage Vop is set in a range between these. Therefore, a voltage value V1 for operating the IJ relay is set between the input voltage VOD during steady operation and the overvoltage protection voltage VOV, and this (1) is detected by the voltage detection device 11 and a signal is output to the relay contact control device 8. The relay 6 is then opened, and the same effect can be obtained.

[Effects of the Invention] As described above, according to the present invention, when the solar cell is outputting an open circuit voltage, the divided voltage is used as the input voltage of the inverter, so that the overvoltage protection operation of the inverter does not work. The input voltage can be limited so as not to cause problems, and accordingly, the withstand voltage level of the main elements of the inverter can be lowered.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the first embodiment of the present invention, Fig. 2 is a relational diagram showing its operation, Fig. 3 is a diagram showing the characteristics of the solar cell, and Fig. 4 is the second embodiment of the invention. FIG. 1... Solar cell, 2... Backflow prevention diode, 3
... Capacitor, 4... First resistor, 5... Second resistor, 6... Relay, 7... Inverter,
8... Relay contact control device, 9... Electric motor, 10
... Pump (load), 11... Voltage detection circuit. Agent Patent Attorney Noriyuki Ken Yudo Hiroshi Mimata Figure 2 Vop Mutake → Figure 3

Claims (1)

[Claims] In a device that uses a solar cell as a power source to excite a motor and drive a load via an inverter, the output voltage of the solar cell is divided by first and second resistors, and the inverter is connected between terminals of the first resistor. A solar power generation device characterized in that a switching device that opens and closes depending on the state of the solar power generator is connected, and the inverter is connected between terminals of the second resistor.