离网条件下的虚拟同步机分布式并联系统暂态稳定分析

Transient stability analysis of virtual synchronous machine distributed parallel system under off-grid condition

虚拟同步机技术的应用,使得分布式电源具有同步发电机特性,可实现离网运行,其可控惯量对离网条件下分布式并联系统的频率稳定和有功振荡有很大的影响。基于离网条件下的虚拟同步机分布式并联系统,以两端输出有功功率振荡为标准,利用李雅普诺夫方法推导暂态能量函数,分析两端惯性时间常数对系统有功振荡的影响。根据分析结果,对暂态期间惯性时间常数进行控制,抑制有功振荡幅度,减小振荡时间,从而提高系统暂态稳定性。最后,利用PSCAD/EMTDC?软件建立模型进行仿真,验证所提方法的可行性。

Because of the application of virtual synchronous machine technology,the distributed generation has the characteristic of a synchronous generator,which can achieve off-grid operation.The controllable inertia has great influence on the frequency stability and active power oscillation of the distributed parallel system under the off-grid condition.In this paper,a distributed parallel system of virtual synchronous machine under off-grid condition is presented.The output active power oscillation at both ends are the standard.The Lyapunov method is used to analyze the influence of inertia time constant at both ends on the active power oscillation of the system.Then based on the analysis result,the inertial time constant is controlled to reduce active power oscillation range and time during the transient period,so as to improve the transient stability of the system.At last,a simulation model is established in PSCAD/EMTDC?to verify the feasibility of the proposed method.