电网不平衡条件下组合式三相单级全桥PFC变换器的运行特性及控制策略

Operating Characteristics and Control Strategy of Phase Module Combined Three-phase Single-stage PFC Converter Under Unbalanced Grid Conditions

首先简要介绍组合式三相单级全桥PFC变换器的电路构成与工作原理,简析该变换器采用常规（电压电流双闭环）控制策略在电网平衡条件下的运行特性。在此基础上,分两种情况详细分析电网不平衡条件下该变换器的运行特性,分析表明采用常规控制策略时,该变换器将同时存在输入电流含低次谐波、输出电压含低次纹波及各相功率不均衡的问题。为解决上述问题,基于电压电流双闭环控制策略提出一种含有两个比例因子和限幅环节的双比例因子（double scaling factor,DSF）控制策略,并分析各组成部分的功能与工作机理。最后,搭建实验平台,对上述内容进行实验验证。实验结果表明,DSF控制策略实现容易、效果良好,可同时解决上述电流谐波、电压纹波和功率不均衡问题。

Firstly, the structure and working principle of phase module combined three-phase single-stage PFC converter were introduced. The operating characteristics while using conventional control strategy（voltage and current double closed loop） were analyzed briefly under balanced grid condition. On this basis, the operating characteristics of the converter under unbalanced grid conditions were analyzed in two cases. The problems of input current low-order harmonic, output voltage low-order ripple and unbalanced power of each phase module were proved to be existed in the converter with conventional control strategy. To solve these problems, double scaling factor（DSF） control strategy, which consists of double scaling factor and a limiter, was proposed on the basis of voltage and current double closed loop control strategy. The function and working mechanism of each component were also analyzed. At last, the experimental platform was built to verify the above contents. The experimental results show that the DSF control strategy is easy to achieve and have a good performance. And the current harmonic, voltage ripple and power imbalance problems can be solved at the same time.