改善虚拟同步发电机阻尼特性的设计方法

Design Method for Improving Damping Characteristics of Virtual Synchronous Generator

虚拟同步发电机(virtual synchronous generators,VSG)控制基于虚拟同步机制可以增大电力系统等效转动惯量,改善电网稳定性。但是由于虚拟同步发电机模拟传统电机的机电暂态特性,传统电机的动态稳定性问题也因此被引入到虚拟同步发电机中。通过建立虚拟同步发电机的动态模型,发现线路电感会对系统等效产生负阻尼力矩;采用复数力矩系数法,分析得到虚拟励磁调节器同样会在控制回路中等效叠加阻尼力矩,存在功率振荡的风险。为改善系统阻尼特性,采用虚拟阻抗控制策略改善电感等效阻尼;并提出一种虚拟电力系统稳定装置(power system stabilizer,PSS)设计方法,可以实现虚拟励磁等效力矩的补偿。最后,通过搭建仿真平台,验证虚拟同步发电机中存在的负阻尼特性以及补偿设计方法的有效性。

Virtual synchronous generator(VSG)control based on virtual synchronization mechanism can increase the equivalent inertia of power system and improve grid stability.However,because VSG simulates the electromechanical transient characteristics of conventional synchronous generator(SG),it also exhibits the dynamic stability problem of SG.This paper established a dynamic model of VSG,and found that line inductance could produce an equivalent negative damping torque to the VSG system.Through analysis using complex torque coefficient method,it is found out that virtual excitation regulator could also superimpose damping torque in control loop,but with the risk of power oscillation.In order to improve the damping characteristics of the system,this paper put forward a virtual impedance control strategy to compensate the equivalent damping of inductance.Besides,a design method of virtual power system stabilizer(PSS)is proposed to compensate the equivalent torque of virtual excitation regulator.Finally,a simulation platform is built to verify the negative damping characteristics of VSG and effectiveness of the compensation method.