Effect of BVSI in Static Synchronous Series Compensator (SSSC) for the Control of Active Power Flow in a Transmission Line

In present a new Static Synchronous Series Compensator (SSSC) for the control of active power flow in a transmission line is proposed and its effectiveness is investigated. The new SSSC is based on injecting a voltage in a given line to counter or augment the voltage & Power produced by the inductive reactance of the line. The resulting compensator, therefore, emulates the control of transmission line reactance and thus, it assists in control by the power transmission capacity. The voltage to be injected in a line is produced by a Binary Voltage Source Inverter (BVSI). BVSI is an attractive recently proposed Voltage Source Inverter. Its output contains very little harmonics and it utilizes very few dc sources unlike conventional multi-level VSIs. The %phase output of the BVSI is synchronized to the line frequency and its phase is arranged to be in or out of phase with the line reactance drop. The proposed BVSI-SSSC is realized by using three binary proportioned dc sources, which may be appropriately dimensioned capacitors. The resulting output of a BVSI-SSSC is a 15-step ac voltage waveform. The BVSI-SSSC has a sophisticated set of coordinated controlled which ensure: BVSI frequency is in synchronism with the system frequency, firing pulses are regulated for inverter valves to ensure minimum harmonic content, the selection of Modulation Index and arrangement regulates an appropriate phase relationship to create the desired change in the power flow, and adjustment of firing angles to ensure that the capacitors creating dc binary proportioned sources maintain desired charge on them. Armillary controls may be added to create positive system damping through active power control and voltage dependent controllers may be added to limit over and under voltage (charging) of capacitors during fault conditions.