Current-source converter based SSSC: modeling and control

The static synchronous series compensator (SSSC) is a series connected FACTS controller, which is capable of providing reactive power compensation to a power system. The output of an SSSC is a series injected AC voltage, which leads or lags the line current by 90/spl deg/, thus emulating a controllable inductive or capacitive reactance. SSSC can be used to reduce the equivalent line impedance and thus enhance the active power transfer capability, of the transmission line. SSSC is conventionally realized with a voltage-source converter. In this paper, an SSSC based on the current-source converter topology is proposed. In this structure, the DC-side current is regulated to a value larger than the peak value of the maximum line current. The injected voltage is controlled according to the desired reactive power compensation. The decoupled state-feedback control for the injected voltage with a separated DC current control is applied to the proposed system. The advantages:of the proposed scheme include fast dynamic response and high quality of current and voltage waveforms. The proposed SSSC has been simulated using the PSCAD/EMTDC package. The simulation results show that excellent current and voltage waveforms as well as very short response times can be obtained while operating at a low switching frequency. This makes the proposed scheme suitable for high power applications.