基于虚拟同步机的变流器暂态稳定分析及混合同步控制策略

针对采用组网型控制策略(以虚拟同步机控制为例)且考虑电流限幅的电压源型变流器(VSC)暂态稳定性差且失稳机理不明的问题,首先从传统同步机的暂态稳定分析方法入手,定性地分析了组网型VSC的暂态过程.然后,通过基于相图的非线性微分方程的分析方法,定量研究了组网型VSC的暂态失稳机理,并提出了一种结合了传统同步机摇摆方程和锁相环的新型同步方法(称为混合同步控制),使得VSC不仅具备频率响应的能力,而且其暂态稳定裕度得到了大幅提高.最后,通过MATLAB/Simulink搭建的仿真模型验证了分析方法的准确性和所提控制方案的有效性.

Transient Stability Analysis and Hybrid Synchronization Control Strategy of Converter Based on Virtual Synchronous Generator

Aiming at the problem of poor transient stability and unclear instability mechanism of the voltage source converter (VSC) that adopts the grid-forming control strategy (take the virtual synchronous generator control as an example) with a current limiting loop, this paper starts with the transient stability analysis of the traditional synchronous generator, and qualitatively analyzes the transient process of the grid-forming VSC. Through the nonlinear differential equation analysis method based on the phase portrait, the quantitative analysis of the transient instability mechanism of the grid-forming VSC is implemented. Moreover, a new synchronization method (called hybrid synchronization control) that combines the swing equation of the traditional synchronous generator and the phase-locked loop is proposed, which makes the VSC not only has the ability of frequency response, but also greatly improve its transient stability margin. Finally, the simulation model built in MATLAB/Simulink verifies the accuracy of the analysis method and the effectiveness of the proposed control scheme.