有限电网容量下大功率变换器的测试方法

Study on the High Power Converter Testing Method in Limited Capacity Power Grid System

基于三相电压源PWM变换器并联拓扑,提出一种对推变流器。通过控制策略使得电流只在对推变流器之间流动,而与电网交互功率几乎为零,从而实现了在有限电网容量下对大功率变换器的测试。建立了对推变流器的数学模型,分析了对推变流器的内部电流通路,得出其内部电流在本质上属于基波环流这一结论。在分析了LCL滤波器对对推变流器控制稳定性的影响以及不同PWM调制方法对对推变流器电流谐波的影响的基础上,给出了对推变流器的控制策略。仿真和实验结果表明了理论分析的正确性。

A new converter termed push-pull converter is proposed based on the parallel topology of the three-phase voltage source PWM converters. In order to realize almost zero interactive power between the grid and the proposed converter, the appropriate strategy is adopted to control the current flowing only inside the proposed converter. In view of aforementioned method, the full-scale power tests of different high-power converters will be implemented in limited capacity power grid system. The mathematic model and the current circuit of the proposed converter are analyzed theoretically to achieve conclusion that the inner current of the proposed converter is the fundamental circulating current in essence. By the way, the effect of the LCL filter to the control stability as well as the influence of the PWM modulation method to the current harmonics of the proposed converter is analyzed independently and the control strategy is presented in detail. In the end, theoretical analysis has been validated by the simulation and experimental results.