JPS6111829A - Control device of output power of inverter - Google Patents

Abstract

PURPOSE:To attain the effective use of a solar battery by comparing an output power of an inverter with a load power, and if the output of the inverter is larger than the load power, compensating the voltage of the solar battery on the basis of the load power. CONSTITUTION:A power detector 14 detects the output power of the inverter 3. A power detector 15 detects the load power of a load 6. An error amplifier 16 outputs zero when the load power P is larger than the output power P1 of the inverter 3, and generates a positive polarity output if the reverse condition is formed. When PL<PI is formed, a constant voltage setting circuit 7 for the solar battery voltage is compensated by the output of the error amplifier 16.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a power control device for an inverter device that uses a solar cell as a DC power source and performs interconnected operation with a power distribution system.

[Background of the invention]

It is clear that in order to maximize the use of solar cell power, the solar cell voltage should always be controlled to the optimum operating voltage according to the amount of solar radiation and solar cell temperature. , even when solar cells are used at constant voltage at the optimum operating voltage under the rated state (solar radiation 100 mW/-1 cell source power 28 C), the power reduction rate is only a few minus compared to the optimum operating voltage control. As said, V6 p because of ease of control.
Constant voltage control is often used. An inverter device having a configuration as shown in FIG. 1 can be considered as an inverter device that can control the output voltage of a solar cell to a constant voltage and can be connected to a power distribution system. In the figure, 1 is a solar battery power source, which is converted into AC by an inverter 3, shaped into a sine wave by a subsequent filter 4, and then connected to the power distribution system 13 by a switch 5. Power is supplied from both inverters 3.

In the control circuit, the inverter output voltage is taken in by the voltage transformer 11, the distribution system voltage is taken in by the voltage transformer 12, and the phase detection circuit 10. The frequency control circuit 9 synchronizes the inverter output voltage phase with the distribution system voltage phase.

On the other hand, the voltage E4 of the solar cell is taken into the control system and compared with the constant voltage setting circuit 7, and the deviation thereof is amplified by the error amplifier 8 and added to the output of the phase detection circuit lo. This)
By controlling the inverter output voltage by changing the four phases of the output voltage of the inverter 3 with respect to the grid voltage phase, the output voltage of the solar cell is controlled to be constant.
However, if the solar battery voltage is controlled to be constant and the solar battery capacity is larger than the load power consumption, the output power of the inverter 3 will be greater than the power consumption of the load 6, and the power will be sent to the distribution system 13. It is possible that the water flows backwards. There are currently problems that need to be resolved regarding the backflow of power into the distribution system, and in most cases backflow is not allowed except in special cases. As described above, when backflow of power is not recognized and backflow of power occurs, the inverter has to be stopped, which is a major drawback in terms of effective use of solar cells.

[Purpose of the invention]

An object of the present invention is to provide an inverter device that performs interconnected operation with a power distribution system that uses solar cells as a power source, and that automatically controls solar cell voltage using load power so that power does not flow into the power distribution system.

[Summary of the invention]

The key point of the present invention is to detect and compare both the inverter output power and the load power, and if one is larger, perform arbitrary voltage control such as constant voltage control or optimal operating voltage control on the solar cell voltage. If this is large, the DC voltage should be controlled to prevent the inverter from outputting more power than the load power by correcting the solar cell voltage based on the load power.

[Embodiments of the invention]

FIG. 2 is a block diagram of an embodiment of an inverter device to which the present invention is applied. The differences in Fig. 2 from Fig. 1 are a power detector 14 that detects the output power of the inverter 3, a power detector 15 that detects the load power, an error amplifier 16 that amplifies the deviation between the two, and the solar cell temperature. Detector 19
, and a changeover switch 18 are provided. The error amplifier 16 receives the output P! of the power detector 14. and power detector 15
The characteristics shown in FIG. 3 are provided depending on the magnitude of the output PL. That is, load power Pp is inverter power P! When the inverter power Pg is larger than the load power P&, the output of the error amplifier 16 is zero. Conversely, when the inverter power Pg is larger than the load power P&, the error amplifier 16 has a positive polarity output characteristic.

When the output of the error amplifier 16 with such characteristics is added to the major loose solar cell voltage setting in a minor loop, Pz,
), during PsO, the solar cell voltage is set by the constant voltage setting circuit 7
will be determined by the value of Also, PL<Ps
In this case, it is possible to correct the solar cell voltage constant voltage setting circuit 7 using the output of the error amplifier 16, change the solar cell voltage, and reduce the output power of the solar cell so that Ps≦PL. can. In general, the relationship between solar cell temperature and optimal operating voltage shows a negative temperature coefficient, as shown in Figure 4, so the solar cell output power can be reduced depending on the relationship between constant voltage setting value and solar cell temperature. The direction of voltage control is different. The constant voltage setting circuit 7 is connected to the error amplifier 1.
When performing correction using the output of 6, 1. The output polarity of the error amplifier 16 must be changed by the method described below. In other words, if constant voltage operation is currently being performed with the voltage at point A in Figure 4, the solar cell temperature Tc is detected by the solar cell temperature comparator 19 and corresponds to the voltage at point A in Figure 4. In comparison with the solar cell Tm, in the case of Tc)Tm,
By directly correcting the constant voltage setting circuit 7 using the output of the error amplifier 16 to increase the solar cell voltage, the output power can be reduced. In addition, the output of the error amplifier 16 is connected to the polarity reversing circuit 17 (by the cutoff switch 18 in the case of Tc), and the polarity is opposite to that of the output of the error amplifier 16 to correct the constant voltage' set value 7. However, the output power can be reduced by lowering the solar cell voltage. . Note that 2 in the figure is a capacitor.

〔Effect of the invention〕

According to the present invention, even when solar cell power becomes greater than load power, backflow of power to the power distribution system can be prevented without stopping the inverter.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a conventional inverter device, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is an error amplifier characteristic diagram for explaining the operation of Fig. 2, and Fig. 4 is a block diagram of an embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the optimal operating voltage and temperature of a solar cell. 14... Power detection circuit, 15... Power detection circuit, 1
6...Error amplifier, 17...Polarity inversion circuit, 18.
...Selector switch, '19...Solar cell temperature comparison circuit.

Claims (1)

[Scope of Claims] 1. In an inverter device that supplies power to a load by using a solar cell as a DC power source and constantly operating in connection with a distribution system to supply power to a load, if the output power of the inverter device is smaller than the load power, the DC voltage constant control or optimal operating voltage control, and if the output power of the inverter device becomes larger than the power consumption of the load, the DC voltage of the solar cell is controlled according to the power consumption of the load. An inverter output power control device characterized by: 2. In claim 1, the output power control device changes the control direction of the operating voltage of the solar cell depending on the relationship between the set value of the DC voltage and the temperature of the solar cell. Inverter output power control device.