Research On Methods Of Analysis For Subsynchronous Resonance Of Power Systems And Its Countermeatures

With the development of “West to East Power Transmission” and large powerinterconnected networks in China, series capacitor compensation are widely used and bringserious subsynchronous resonance (SSR) problem. It is of great significance for theoreticalresearch and engineering practice to study SSR mechanisms as well as its analytical methodintensively and adopt effective measures for restraining. In this paper, analytical methodand countermeasures of SSR are focused. On the one hand, a promoted method of complextorque coefficient is used to meet the requirement of SSR analysis in large scale system,and the method is verified by time domain simulation. On the other hand, a control methodof static synchronous compensator (STATCOM) for SSR damping is explained in detail aswell as its inhibition mechanism.A method of complex torque coefficient which takes the shafts dynamic and speeddeviation into account for electrical damping calculation was introduced in this paper.Based on complex frequency domain port-equivalence conductance matrix (CPCM), thismethod forms network equation conveniently, and reduces the computational complexityeffectively. The SSR character of multiple typical systems and its damping effect by staticvar compensator(SVC) were researched, and verified by time domain simulation. Theresearch proposes that the shafts dynamic and speed deviation must be taken into account.And the method can modify network equation quickly and conveniently, which makes itadaptive for researching SSR of complex power system.Furthermore, a control strategy of STATCOM based on supplementary voltage controlfor SSR damping is proposed, and its mechanism is deduced mathematically in detail. Then,the proposed control scheme is tested on a typical series-compensated transmission systemby simulation. The results demonstrate its effectiveness in damping multimodal SSR. Thecomparison between STATCOM and SVC indicates that with same capacity, STATCOMgains better effect over SVC in damping SSR. The results are helpful to solving thesubsynchronous resonance problems which exist in the series compensated transmissionsystems in China and abroad. And the conclusions also provide valuable references forbetter applications of the STATCOM.