Low-common-mode-noise grid-connected inverter circuit and reactive power control method

Abstract

The invention relates to a low-common-mode-noise grid-connected inverter circuit and a reactive power control method. The low-common-mode-noise grid-connected inverter circuit comprises an enhanced voltage-reducing chopper circuit and a silicon controlled rectifier power frequency phase-changing circuit, wherein the enhanced voltage-reducing chopper circuit comprises a power switch tube modulated through sinusoidal pulse width modulation (SPWM), a double-follow-current diode, a power-factor control power switch tube, an inductor and a capacitor. The direct current electric energy is converted into sine semiwaves by adjusting the duty ratio of high-frequency switch tubes in the enhanced voltage-reducing chopper circuit. The power-factor can be adjusted by adjusting a conducting mode of the power-factor control power switch tube. The phase-changing circuit consisting of four low-frequency silicon controlled rectifiers performs phase changing on the direct current sine semiwave to obtain full sine waves and finishes inversion from the direct current to the sine alternating current. Compared with conventional full-bridge grid-connected inverter circuits, the low-common-mode-noise grid-connected inverter circuit is simple in structure, strong in overcurrent-resisting capacity, high in stability and inversion efficiency and low in cost, and the number of the high-frequency switch tubes is approximately decreased by one half. Due to the fact that a whole inversion loop is fully symmetrical in the switching and phase-changing process, the common-mode voltage produced by inverted alternating-current output is constant, the common-mode current is restrained, and electro-magnetic interference (EMI) is reduced.

Description

technical field [0001] The invention relates to a grid-connected inverter circuit with low common-mode noise and a reactive power control method, especially a DC / AC grid-connected inverter with high conversion efficiency and low harmonic distortion, and capable of power factor adjustment at the same time. Transformer circuit and reactive power regulation method. Background technique [0002] The function of the grid-connected inverter circuit is to convert the DC voltage into a sinusoidal AC, and realize the grid-connected power 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. [0003] 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....

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 amplitude

In a unipolar modulation circuit, the amplitude of the common-mode voltage generated by the inverter varies greatly, and the resulting common-mode current increases linearly with the increase of the switching frequency, and the harmonic distortion and common-mode noise interference are serious

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