Method for synchronization of three-phase parallel type inversion module

Abstract

A three-phase parallel-connection reversal module synchronization method is provided. In a system, each reversal module realizes free competition by seizing a bus to confirm a host machine and an auxiliary machine. The main machine and the auxiliary machine respectively take a bypass voltage and a main machine output voltage as a phase locking tracking source. Each module samples a three-phase tracking source and a three-phase output voltage and calculates frequency of the tracking source voltage and the output voltage, frequency difference and phase difference. Based on the frequency difference between the tracking source and the output voltage, look-up length of a PWM modulation sine wave is adjusted to gradually fix frequency of the tracking source. And then, the look-up length of the PWM modulation sine wave is slightly adjusted according to the phase difference between the tracking source and the output voltage to reduce phase difference between them and fix the phase. Asynchronous pulse is transmitted at a zero passage of a main counter through the main machine. The auxiliary machine captures the pulse and sends the pulse to a rectification method of the main counter for carrier wave synchronization. The present invention solves a problem of three-phase locking and eliminates high-frequency component in circulating currents.

Description

technical field [0001] The invention relates to the field of three-phase modular parallel inverter power supply, in particular to the synchronization of three-phase parallel uninterruptible power supply systems. Background technique [0002] At present, the AC power supply mode is developing from centralized to distributed and full-featured. A power system composed of multiple inverter modules connected in parallel has become a promising engineering application scheme. This parallel redundant system has the following advantages: reliable operation, wide power range, extremely high system maintainability, and when a module fails, it can be easily replaced or repaired by hot swapping. The technical key is the synchronization of each inverter module, that is, the output voltage of each inverter module should meet the same amplitude, same frequency and same phase, so as to achieve the requirements of equal load sharing and zero circulating current. [0003] The circulating cur...

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Problems solved by technology

Due to the difference in power-on time and the drift of the crystal oscillator, the PWM (Pulse Width Modulation, Pulse Width Modulation) carrier of each inverter module will not be able to guarantee synchronization, resulting in high-frequency components, which are extremely difficult to eliminate in a distributed control parallel system

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