Paralleling Multiple Static Synchronous Series Compensators Using Daisy-Chained Transformers

A modular and scalable series compensation technique for enhancing controllability and flexibility in power transmission in distributed power systems is proposed. The concept is based on paralleling multiple static synchronous series compensators (SSSC) through daisy-chained transformers to perform reactive power compensation, and thus control the amount and direction of the power flow over the transmission link. Each compensator unit is under an autonomous control for regulating its output voltage. Its output current is coupled to another compensator unit through one of the daisy-chained transformers, so that the transmission current is shared among the parallel-connected compensators. Modeling, design, and analysis of a compensator unit and the proposed multiparallel-connected SSSC (MSSSC) architecture in an elementary two-machine system will be presented. A 3-kVA MSSSC test bed with three-parallel-connected compensator units for a single-phase system has been built and evaluated. The steady-state and transient current-sharing characteristics in forward and reverse power transmission over the transmission link will be studied. The response of the MSSSC system with each compensator unit engaged sequentially will also be investigated.