Fault-Tolerant Transformerless Power Flow Controller Based-on ETO Light Converter

Static Synchronous Series Compensator (SSSC) is one of the solid state Flexible AC Transmission System (FACTS) devices which is effective to control the active power flow across the transmission lines by altering or changing the characteristic impedance of the power line. However its widespread application is still limited by higher cost, series protection requirements, and low reliability. Attention is drawn to the issues of fault-tolerance and distributed design of the SSSC to achieve high reliability and lower cost. In this paper, a new 1-2 MVA modular ETO Light converter with low cost and high power density is introduced. Combined with modular air-cooled heat-pipe, modular digital interface, this modular converter has self-sensor, self-power and self-protection functions. The high voltage/current rating and control power self-generation enable the transformerless connection. Two fault-tolerant power flow controllers based on ETO Light converter are proposed. The SSSC operating principle and control strategies are introduced and discussed. The proposed protection scheme and SSSC controller operation is validated by simulation results. Full scale hardware demonstration is underway and experimental results will be presented in the final paper. Some experimental test results of ETO Light converter are also presented.