控制延时对虚拟同步机全局稳定性的影响分析

Analysis of Influence of Control Delay on Stability of Virtual Synchronous Machine

虚拟同步机(virtual synchronous generator,VSG)控制技术可使并网逆变器模拟传统同步发电机运行,应用前景广阔。VSG控制依托数字控制技术实现,存在数字控制固有的控制延时问题,制约系统的响应特性和控制精度,影响系统的稳定性。现有研究多局限于分析数字控制延时对控制系统局部稳定性的影响,鲜有文献涉及延时对系统全局稳定性的影响。研究了一种基于状态空间建模和灵敏度分析的逆变器延时稳定性分析方法。首先,建立基于VSG控制的逆变器全阶状态空间模型,包括数字控制延时、内部电压电流控制环、基于VSG控制的功率外环以及物理环节;然后,借助特征值和灵敏度分析,评估控制延时对系统全局稳定性的影响。在此基础上,给出使系统稳定的临界延时时间。仿真和实验结果验证了文中理论分析的正确性,文中所述方法可以为逆变系统参数设计提供理论参考依据。

Virtual synchronous generator(VSG) control technology, making grid-connected inverters simulate operation of traditional synchronous generators, has broad application prospects. Relying on digital control technology, VSG control has the inherent control delay problem of digital control, restricting the response characteristics and control accuracy of the system and affecting system stability. Most of existing studies are limited to analyze the impact of digital control delay on only one part of the control system. In this paper, a state space model of high-order small signal is established for VSG system considering control delay. Based on the model, the root trajectory of the system characteristics is obtained, stability of the inverter under different delays is analyzed, and then the critical delay time of the system stability is given. Simulation and experimental results verify correctness of the theoretical analysis in this paper. The method presented in this paper provides theoretical reference for parameter design of inverter system.