DC/AC grid connected inverter circuit and power factor adjusting method

Abstract

The invention relates to a DC/AC grid connected inverter circuit and a power factor adjusting method. The DC/AC grid connected inverter circuit comprises an enhanced voltage reduction chopper circuit and a controlled silicon power frequency phase inverter circuit, wherein the enhanced voltage reduction chopper circuit comprises an SPWM (Sinusoidal Pulse Width Modulation) modulated power switch tube, a double freewheel diode, a power factor adjusting power switch tube, an inductor and a capacitor. Direct current is converted into a half sine wave by adjusting the duty ratio of the high frequency switch tube in the enhanced voltage reduction chopper circuit; and power factor adjustment can be realized by adjusting the conduction mode of the power factor adjusting power switch tube. The direct current half sine wave is subjected to phase inversion by the phase inverter circuit composed of four low frequency controlled silicon to obtain a full sine wave so as to finish inversion from direct current to sine alternating current. Compared with the traditional full bridge grid connected inverter circuit, the grid connected inverter circuit provided by the invention is simple in structure, strong in overcurrent resistance, high in stability, high in inversion efficiency and low in cost, and the number of high frequency tubes is reduced by half. In the switching and phase inverting process, a constant common mode voltage is produced from the alternating current output of the inverter, so that the common mode current is inhibited and the EMI (Electro-Magnetic Interference) interference is reduced.

Description

[0001] technical field [0002] The invention relates to a grid-connected inverter circuit and a control method, in particular to a DC / AC grid-connected inverter circuit with high conversion efficiency, low harmonic distortion and power factor adjustment and an adjustment method. Background technique [0003] The function of the grid-connected inverter circuit is to convert the DC voltage into a sinusoidal AC, and realize grid-connected supply for electrical equipment. High efficiency and low harmonic distortion are the key indicators of this technology; when connecting to the grid for power generation, it is also necessary to adjust the power factor according to the power dispatching instruction. [0004] The existing grid-connected inverter technology mostly adopts a four-tube full-bridge circuit structure, such as figure 2 Shown, using bipolar modulation or unipolar modulation. In the bipolar modulation circuit, the four switching tubes (shown in the dotted line box) al...

AI Technical Summary

Problems solved by technology

In the bipolar modulation circuit, the four switching tubes (shown in the dotted line box) all work at a relatively high switching frequency, the loss of the switching tube is large, which affects the efficiency, and there is a large switching noise and current ripple

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