构网型变流器多环控制阻抗建模与稳定性分析

Impedance Modeling and Stability Analysis for Multi-loop Control of Grid-forming Converter

构网型变流器的控制方式按照是否存在电压电流控制双环可以分为只含有功率控制环的单环控制和含有功率控制环和电压电流控制双环的多环控制。两种控制方式并网运行特性在不同频段有较大区别。该文首先建立考虑电压电流解耦控制双环的构网型变流器多环控制序阻抗模型,对比分析两种控制方式对变流器输出阻抗的影响;其次针对加入电压电流控制双环造成的低频相位裕度不足问题,提出引入虚拟阻抗方法提高变流器并网稳定性;最后利用仿真与实验验证了稳定性分析的准确性。

The control method of grid-forming converter can be divided into single loop control with only power control loop and multi loop control with power control loop and voltage and current control dual loop based on the existence of voltage and current control dual loops.There are significant differences in the characteristics of grid connected operation between the two control methods in different frequency bands.This article first establishes a multi loop control sequence impedance model for a grid type inverter considering voltage and current decoupling control,and compares and analyzes the impact of two control methods on the output impedance of the inverter.Secondly,to address the issue of insufficient low-frequency phase margin caused by the addition of voltage and current control dual loops,a virtual impedance method is proposed to improve the stability of the converter grid connection.Finally,the accuracy of stability analysis was verified through simulation and experiments.