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The IUP Journal of Electrical and Electronics Engineering:
Fuzzy Logic Controller-Based SSR Mitigation in Turbine-Generator shaft Using SVC
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Subsynchronous Resonance (SSR) oscillations in a power system are most unwanted phenomenon. The interaction between torsional system and electrical system exhibits a situation of SSR oscillations. These oscillations, if not sufficiently damped, grow tremendously, leading to stability problem. Though Power System Stabilizer (PSS) damps subsynchronous oscillations effectively over the period of time, still oscillations due to SSR remain a challenge to it. Flexible AC Transmission System (FACTS)-based compensators play an important role in mitigating SSR oscillations most comprehensively. The paper proposes a fuzzy tuned Static VAR Compensator (SVC) for analyzing the SSR phenomenon in an IEEE Second Benchmark Multimass (ISBM) system. An ISBM model with SVC is carefully designed using Fuzzy Logic Damping Controller (FLDC) for SSR analysis using MATLAB/Simulink. The simulated results showed higher convergence rate and better SSR damping capability.

 
 

Series compensation in a long transmission line is a cost-effective solution for increasing power transfer problem, increasing voltage profile of transmission lines enhancing steady state stability of system and lastly controlling the load sharing among parallel lines. However, use of fixed series compensation introduces some new problems in power system operation. When series compensation is employed to steam Turbine-Generator (T-G) set, the interaction between mechanical and an electrical system initiates a phenomenon called Subsynchronous Resonance (SSR). A wide range of SSR modes can be excited by perturbations and switching events in most of the electrical and torsional systems. Because of net positive damping, most of these oscillations are harmful and die out. However, under certain situations, some specific oscillations may have unacceptably high magnitude. This oscillation may further rise or sustain for a long period. This results in T-G shaft damage due to fatigue, insulation failure, mechanical aging or breakdown or system instability. When the oscillations involve both the electrical and rotating mechanical equipment coupled through magnetic flux, frequencies below power frequency appear. Mechanical oscillations are present among individual turbine masses and generator coupled through long shaft. When these torsional modes are electrically coupled with transmission line through synchronous generator, subsynchronous oscillations are excited in the range of 10-50 Hz.

 
 
 

Electrical and Electronics Engineering Journal, SMIB, Subsynchronous Resonance (SSR), Static VAR Compensator (SVC), Low frequency oscillation, Power System Stabilizer (PSS).