Effect of subsynchronous resonances on Hydro-Québec static var compensators

Stability of the static var compensators on the future series-compensated Hydro-Québec network has been studied by means of frequency domain and time domain techniques. Interaction between shunt and series compensation produce poorly damped subsynchronous transient voltages. Simulator and EMTP studies have shown that transformer saturation resulting from the addition of subsynchronous voltages has a major impact on the static var compensator behavior, resulting in oscillation modes not foreseen by eigenvalue programs. This paper will focus on the interactions between network subsynchronous modes, transformer saturation and SVC control systems.