Fault detection method of cascaded grid-connected inverter unit based on pulse voltage comparison

Abstract

The invention discloses a cascaded grid-connected inverter unit fault detection method based on pulse voltage comparison. The method is applicable to a carrier phase-shifting pulse width modulation (PWM) mode, and comprises three steps of output alternating voltage conditioning and sampling, detection condition judging and fault judging and positioning. An output phase voltage of a cascaded grid-connected inverter is subjected to analog / digital (A / D) sampling through a sensor and a conditioning circuit; when the output phase voltage of the inverter is a direct current side voltage of a single H-bridge unit, the fault can be judged and positioned through simple comparison according to a carrier phase-shifting PWM principle. According to the method, only the output three-phase voltage is required to be sampled and simply compared, so that a direct current side voltage value of the H bridge unit of the cascaded inverter can be rapidly and accurately obtained, the fault is further judged, the fault judgment can be conveniently realized through software, the cost is saved, the efficiency is improved, and the method has high research and application values in aspects of real-time fault detection and direct current side voltage balance control of the cascaded grid-connected inverter.

Description

technical field [0001] The invention belongs to the technical field of application of high-voltage and high-power power electronic technology in power systems, and relates to a unit fault detection method of a cascaded grid-connected inverter under a carrier phase-shifting PWM modulation mode. Background technique [0002] In recent years, with the development of new energy technology and power electronics technology, the H-bridge cascaded structure has become a research hotspot in the fields of grid-connected inverter, energy storage, and power electronic transformers. The H-bridge cascaded inverter has the advantages of large power capacity, small switching device stress, low harmonic content, modularization and easy expansion, etc., so it is widely used in various electrical devices. [0003] Although the cascaded grid-connected inverter has been successfully applied in many aspects, there are still some points to be improved: because the cascaded structure adopts the for...

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Problems solved by technology

At present, there are few researches on fault detection of cascaded grid-connected inverters at home and abroad. Considering that cascaded grid-connected inverters generally adopt carrier phase-shift PWM modulation, the output phase voltage is multi-level The superposition of the H-bridge unit DC side voltage value can be indirectly obtained by detecting the output phase voltage of the cascaded grid-connected inverter, so as to carry out fault judgment and location

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