Modeling and Control of the Static Synchronous Series Compensator under Different Operating Modes

This paper evaluates the dynamic performance of the static synchronous series compensator (SSSC) functioning under different operating modes. The SSSC uses a voltage source inverter to inject a series voltage in to the transmission line which is kept in quadrature with the line current. By adjusting the magnitude of this injected voltage, the active power flow through the line can be manipulated at will. The magnitude of the injected voltage can be set by commanding a value for the power through the line, a value of the injected voltage itself, or a value for the equivalent impedance seen by the line. This leads to three different operating modes, namely power mode, voltage mode and impedance mode. A dynamic model that allows controller design and performance evaluation under different modes is developed. Detailed computer simulations are used to contrast the performance of the SSSC under these three forms of operation.