JPS5869470A - Control circuit for system interlocking inverter - Google Patents

Abstract

PURPOSE:To simplify the configuration and the regulation of a circuit by controlling a converter which converts the DC output of a solar battery or the like to AC and feeds it to an AC power source system by multiplying the detected system voltage by the instructed power amount. CONSTITUTION:The DC energy of a solar battery 1 is supplied through an inverter 2 in which switching elements S1-S4 are connected in a bridge and an AC reactor 15 to an AC power source system 3. At this time the system voltage of a sinusoidal waveform is detected by PT14, is multiplied by a multiplier 17 by the DC amount of a power instruction unit 4 for calculating and instructing the adequate power amount of the solar battery 1 with the value and the sunshine amount, the output of the multiplier and the output current detected value of the inverter are inputted to a control circuit 16, thereby controlling the ON and OFF of switching elements S1-S4. Accordingly, the circuit configuration can be simplified without necessity of preparing a sinusoidal wave oscillator, and the operation of the power factor 1 can be performed with good rapid responsiveness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit for a grid-connected inverter that converts direct current energy generated by a solar cell or the like into alternating current and sends the converted alternating current to an alternating current power supply system.

FIG. 1 shows a conventional control circuit of this type. 1 is a solar cell, and the DC energy generated by this is transferred to an inverter 2.
The inverter 2 is connected to the AC power supply system 3 via the AC reactor 12. Reference numeral 04 is a power command device, which generates a reactive power command value and an active power command value.

At the connection point with the system 3, it is sent from the inverter 2.

IE force #4T1B, P'l'14* and power calculator 10
i (therefore detected. That is, the power calculator 10 detects active power and reactive power. The reactive power detection value detected by the power calculator 10 is the reactive power command value of the power controller Abh et al. and is guided to the reactive power regulator 5@
The reactive power regulator 5 outputs a voltage command value according to the deviation between the command value and the detected value of reactive power. This voltage command value is PT
It is led to the voltage regulator 6 along with the detected inverter output voltage value taken out via II. On the other hand, the active power detected by the calculator 10 is guided to the active power regulator 7 together with the active power command value from the command @4, and this regulator 7 adjusts the active power according to the deviation between the active power command value and the detected value. It generates an output voltage and supplies it to the voltage controlled oscillator 8. Reference numeral 9 denotes a control unit that controls the controllable valves in the inverter using the output of the voltage controlled oscillator 8 as a phase command and the output of the voltage regulator 6 as a voltage command.

With such a configuration, the electric power sent from the inverter 2 to the grid 3 can be controlled as desired. However, this conventional control circuit has disadvantages in that it is not only complex in structure, but also relatively difficult to adjust.

An object of the present invention is to provide a control circuit that is simple, easy to adjust, and can easily operate an inverter with a power factor l.

Hereinafter, the present invention will be explained in detail with reference to the embodiment shown in FIG.

According to the embodiment of the present invention shown in FIG.
1-84. Each switch element 81 to S4
consists of, for example, a transistor and a diode connected in antiparallel to the transistor. It is preferable that the inverter 2 includes an AC reactor 15 inserted between the AC power supply system 3 and the AC reactor 15 . The power command unit 4 calculates and commands the appropriate amount of power that can be taken from the battery based on the amount of solar radiation, battery voltage, etc. The grid voltage is detected via a voltage transformer (PT) 14, and multiplied by a power command value from the power command device 4 in a multiplier 17. Since the magnitude of the grid voltage can be considered constant, the output of the multiplier 17 is the DC power command value output from the power command unit 4 converted into an AC current command value with the same waveform as the grid voltage. becomes. The current command value, which is the output of the multiplier 17, is guided to the inverter switch control circuit 16 together with the inverter output current detected by the current transformer 13. This control circuit 16 performs on/off control of switch elements 81 to S4 of the inverter 2 so that the detected inverter output current value matches the current command value. Therefore, the output voltage of the inverter 2 is automatically pulse width modulated, and the inverter 2 sends an output current having a sinusoidal waveform that is in phase with the grid voltage to the grid. In this case, the operating power factor of the inverter is always kept at J(1).

If the phase shifter 19 is inserted as shown by the broken line in Figure 2, the inverter can be operated with a power factor that corresponds to the phase shift characteristics of the phase shifter 19. Further, although the embodiments show a single-phase case, it goes without saying that the present invention can also be applied to a three-phase case.

As described above, according to the present invention, the current command value is generated by the product of the sinusoidal waveform grid voltage detection value and the DC power command value, so there is no need to prepare a sine wave oscillator and the circuit configuration can be simplified. It is simple, the current command value - therefore, the inverter output current flows almost instantly, and has excellent coordination, and operation with a power factor of 1 can be performed without complicated adjustments - and can be adjusted arbitrarily by inserting a phase shifter. It is also difficult to operate at a power factor of .

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional embodiment, and FIG. 2 is a block diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Solar cell, 2...Inverter, 3...AC power supply system, 4...Power command unit, 13...Current transformer, 1
4... Voltage transformer, 17... Kakeishi, 19... Phase shifter. 71 Figure

Claims (1)

[Claims] An inverter for grid connection that converts DC energy generated by a solar cell or the like into AC and sends it to an AC power system includes means for detecting the voltage waveform of the AC power system, and a power command value multiplied by a detection signal of the means. A control circuit for an inverter for grid connection, characterized in that it comprises means for creating an inverter output current command value by adding and combining, and means for controlling the inverter output current according to the command value created by the scissor means. .