小增益闭环系统稳定性分析方法及其在含并网VSC电力系统中的应用

Stability Analysis Method of Small Gain Closed Loop System and Application in Power System Connected With VSC

该文首先采用小增益闭环系统模型描述并网电压源型变换器(voltage source converter,VSC)与交流电力系统间的动态交互特性,建立含并网VSC的交直流混联电力系统线性化模型,提出适用于分析并网VSC的小增益闭环系统稳定性分析方法。采用泰勒定理证明在一般情况下,并网VSC与交流电力系统间呈现弱动态交互特性,但是当并网VSC控制环节的开环模式与交流电力系统的开环模式接近时,其对应的闭环振荡模式将会在复平面上发生排斥现象,并在2个开环模式距离最近时达到排斥峰值。以含并网VSC的3机9节点电力系统为例,采用模式分析法和时域仿真法,验证VSC引起次同步振荡的机理分析过程,刻画能够保证系统稳定运行的VSC控制参数范围,展现小增益闭环系统稳定性分析方法在含并网VSC电力系统中应用的有效性和准确性。

The interaction between voltage source converter(VSC)and AC system was described by the model of small gain closed loop system in this paper,based on established AC/DC hybrid power system linearization model,a method of small gain closed loop system for stability analysis was proposed.The stability criterion was proved by Taylor’s theorem and concluded that the closed-loop modes of small gain system will repulse strongly when the open-loop modes of sub-systems are close to each other and the biggest reputation will occur at the point that open-loop modes of sub-systems are equal in complex plane.Finally,the 3 machines and 9 nodes model power system connected with a VSC system was used to verify the process of theoretical analysis and show the applications in the area of sub-synchronous oscillation mechanism analysis and the setting of suitable control parameter by modal analysis and time domain simulation.