基于可控等效输出阻抗的微网逆变器并联特性研究

针对低压微网中采用传统下垂控制的并联逆变器功率均分效果差以及母线电压和频率偏移问题，分析了并联逆变器的环流和功率输出特性，提出一种基于可控等效输出阻抗的微网逆变器并联控制策略。该策略实现了逆变器等效输出阻抗的精确可控，且具有虚拟同步发电机的基本特性，逆变器等效电压源的频率和相位能够实现自同步功能，在不需要功率环的情况下间接实现了并联逆变器功率均分且具有环流抑制能力。通过设计电压二次调节控制，消除了微网母线电压和频率的偏移问题。仿真结果验证了所提控制策略的可行性和有效性。

Research on microgrid inverters parallel characteristic based controllable equivalent output impedance

In view of the poor power sharing of parallel inverters using traditional droop control and the bus voltage and frequency deviation problem in the low-voltage microgrid, the circulating current and power output characteristics of parallel inverters are analyzed, and a control strategy for parallel inverters based controllable equivalent output impedance is proposed. The strategy makes the inverter has a precise controllable equivalent output impedance and has the basic characteristic of the virtual synchronous generator, and the frequency and phase of the equivalent voltage source are capable of self-synchronization function, then it achieves power sharing indirectly without using power ring and has the ability to inhibit the circulating current. It eliminates the bus voltage and frequency deviation problem by designing the secondary voltage regulation control. The simulation results verify the feasibility and effectiveness of the proposed control strategy. This work is supported by Natural Science Foundation of Shanghai (No. 16ZR1413000) and Shanghai Engineering Research Center of Green Energy Grid-connected Technology (No. 13DZ2251900).