A soft grid-connected method for a grid-connected converter

Abstract

The invention provides a soft grid connection method of a grid-connected converter. The method is characterized in that the closed-loop control of the filtering capacitance and the filtering voltage is carried out synchronously; the current inter-loop control is added; and DC pre-charging return circuits are separated and boosted. According to the invention, the non-impact grid connection is realized without increasing great hardware complexity, thereby overcoming the defects of the traditional grid-connected method and improving the reliability of the grid-connected converter.

Description

technical field [0001] The invention relates to the soft grid-connected field of grid-connected converters. Background technique [0002] With the deteriorating world energy crisis and environmental pollution, the large-scale development and utilization of new energy represented by wind energy and solar energy has become an urgent need to alleviate the energy and environmental crisis. With the development of power electronics technology, new energy grid-connected access mostly adopts PWM grid-connected converters, whose DC side is a DC support capacitor to stabilize the DC bus voltage, and the AC side mostly uses LCL filters to suppress high-frequency harmonics Current, so that the energy fed into the grid meets the power quality requirements. [0003] As the key link between new energy and the grid, the grid-connected converter is the key equipment for grid-source coordination in the construction of a smart grid. It is grid-connected without impact and seamlessly connected...

AI Technical Summary

Problems solved by technology

[0006] 1. The influence of the DC soft-start current-limiting resistor limits the maximum voltage of DC pre-charging;

[0007] 2. The AC filter capacitor is synchronized with the grid voltage, adopts open-loop control, and the amplitude and phase still have a certain deviation from the grid voltage, and after the circuit breaker is closed, there is an open-loop control dead zone, and the DC bus capacitance is small , causing the bus voltage to pump up;

[0009] 4. After the filter capacitor synchronization is completed, after the circuit breaker is closed, and before the soft-start contactor is disconnected, there is a large high-frequency zero-sequence circulating current between the soft-start circuit and the main circuit, which reduces the reliability of the soft-start circuit and lifespan

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