An overcurrent protection scheme for series active compensators

A protection scheme for a series active compensator, which is composed of unified power quality conditioner (UPQC) or hybrid active power filter, is presented and analyzed in this paper. The proposed series active compensator operated as a high impedance "k(/spl Omega/)" to the fundamental components when overcurrent occurs in the power distribution system, and three control strategies are proposed in this paper. The first is the method of detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in synchronous reference frame (SRF) and the third is the method by detecting the input voltage. When the overcurrent occurs in the power distribution system, the proposed scheme protects the series active compensator without additional protection circuits. The validity of the proposed protection scheme is investigated through experimental results in the hybrid active power filter systems.