基于虚拟阻抗的两级式单相逆变器二次纹波电流传播特性

Second-Order Harmonic Current Propagation Characteristics in Two-Stage Inverter Based on Virtual Impedance

两级式单相逆变器的输出瞬时功率包含两倍于输出电压频率的脉动功率,致使前级直直变换器的输入存在二次谐波电流。前级直直变换器控制环路的优化是解决该问题的有效且低成本的方法。首先,通过环路等效给出单环控制和双环控制的等效电路模型,利用虚拟阻抗的概念,分析了电压外环和电流内环在二次纹波电流传递过程中的作用。在此基础之上,统一归纳了现有控制策略的抑制原理,指出了各自存在的局限性,并相应地给出了优化方案。最后,利用1500 VA的两级式单相逆变器模型进行仿真,验证了分析方法的可行性及各个控制策略优化的有效性。

The instantaneous output power of a two-stage single-phase inverter pulsates at twice the output voltage frequency,generating second harmonic current(SHC)in the front-end dc-dc converter.The optimization of loop control of the front-end dc-dc converter is an effective and costless method for this problem.This study gives equivalent circuit model of the front-end dc-dc converter with single voltage loop control and voltage current dual-loop control first.Then,the propagation characteristic of the SHC is analyzed from the point of virtual impedance.On this basis,this study proposes a synthesis of different control strategies for SHC reduction and points out the limitations of them.In the view of this,this paper presents corresponding optimization methods.Finally,a 1500-VA prototype model is built and simulated,and the simulation results are presented to verify the effectiveness of the analysis and the optimization.