Performance of STATCOM-ES in Mitigating SSR

Abstract

One of the advanced power applications using energy storage is the integration of energy storage technologies with VSC-based FACTS controllers. With the support of energy storage device, FACTS controllers will have the ability to exchange active power or energy with the ac network in steady state. This paper discusses the impact of Static Synchronous Compensator incorporating energy storage device (STATCOM-ES) on subsynchronous resonance (SSR). It also proposes the design of an auxiliary SSR damping controller (SSDC) for STATCOM-ES to damp the subsynchronous oscillations which the system is undergoing because of a series capacitor in the transmission system. The system under consideration is IEEE FBM which is modified to incorporate STATCOM-ES at the electrical midpoint. The investigation of SSR characteristics when a STATCOM -ES operating in bus voltage regulation mode is carried out by eigenvalue and damping torque analysis. Transient analysis based on the nonlinear model is also performed to validate the results obtained by conventional methods. Keyword:Damping INTRODUCTIONSubsynchronous Resonance (SSR) is a power system phenomenon which occurs due to the interaction between mechanical system of turbo-alternator and series compensated transmission line resulting in failure of shaft [1]. The behavior of the system undergoing SSR can be analyzed using linear and nonlinear techniques. With the advent of FACTS controllers, it is possible to have control over the AC transmission system parameters [2].Static Synchronous Compensator (STATCOM) is a VSC-based shunt FACTS controller whose objectives are the improvement of dynamic voltage regulation and stability of the system. A capacitor supported STATCOM has only one control variable which is the reactive current whereas a battery supported STATCOM has two control variables namely active and reactive current [3]. An auxiliary supplementary controller is required to damp the torsional oscillations. The design of subsynchronous damping controller (SSDC) for FACTS controllers is reported in [4][5][6][7][8][9]. The efficacy of integrating energy storage devices like a battery, fuel cell, supercapacitor etc., to the dc link of STATCOM in enhancing the performance of STATCOM is demonstrated in [10][11][12]. The authors have shown that there is improvement in dynamic and transient stability of the system by incorporating energy storage at the dc side of STATCOM. But the effect of STATCOM incorporating energy storage (STATCOM-ES) on SSR characteristics has not been investigated till now. Hence, the design of SSDC for STATCOM-ES to mitigate SSR is not yet reported.The objective of this paper is to investigate the effect of STATCOM-ES on a power system which is undergoing subsynchronous resonance and design a subsynchronous damping controller to mitigate torsional

Fuzzy Logic Controlled Statcom With a Series Compensated Transmission Line Analysis

“…However, as wind power is usually located far away from the load distribution centers near the consumers, power transportation over long distances becomes a significant problem [4]. Hence, using a series compensation capacitor, a large amount of wind power is transmitted to the grid with higher stability [5][6][7][8]. However, integrating this series compensation in the transmission line will cause oscillations at a particular frequency.…”