基于虚拟阻抗的两级式逆变器二次纹波电流传播特性及抑制策略

两级式单相逆变器的输出瞬时功率包含2倍于输出电压频率的脉动功率，致使前级DC/DC变换器的输入存在二次纹波电流。前级DC/DC变换器控制环路的优化是解决该问题有效且低成本的方法。通过环路等效，给出了单环控制以及双环控制的等效电路模型，基于虚拟阻抗的概念分析了电压外环以及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，解释并归纳了现有控制策略的抑制原理，指出其中存在的局限性，并给出了2种优化方案。最后，构建了1.5 kVA两级式单相逆变器原理样机进行了仿真及试验验证，验证了分析方法的可行性以及控制策略优化的有效性。

Analysis of the Second-Order Harmonic Current in Two-Stage Inverter Based on Virtual Impedance

The instantaneous output power of the two-stage single-phase inverter contains the pulsating power whose frequency is twice as much as the output voltage frequency. For this reason, the secondary ripple current exists in the input of the front-stage DC/DC converter. The control loop optimization of the pre-stage DC/DC converter is an effective and low-cost method to solve this problem. The equivalent circuit models of single loop control and double loop control are given through loop equivalence. Based on the concept of virtual impedance, the functions of voltage outer loop and current inner loop in secondary ripple current transfer process are analyzed. On this basis, the suppression principles of the conventional control strategies are explained and summarized, the limitations of existing control strategies are pointed out, and two optimization schemes are given. Finally, a 1.5 kVA two-stage single-phase inverter prototype is built for simulation and experimental verification, which verifies the feasibility of the analysis method and the effectiveness of the control strategy optimization.