A Control Strategy to Eliminate Interaction between the Series and Parallel Compensator of UPQC

Firstly, the reasons of the interaction between series and parallel compensator of UPQC on account of external electric connection were analyzed in detail, based on that, basic undertakings to cancel the interaction were presented in order to increase control accuracy and decrease steady-state error. Next, the indirect control strategy of three-phase wire UPQC in d-q-0 coordinates was discussed in detail. In order to eliminate the interaction existing in series and parallel side, a two-closed-loop with voltage feed forward control scheme was presented for series compensator and a load voltage feed forward with state discoupling control strategy for shunt compensator. A principle analysis of the proposed control strategy was described in particular. Then the simulation waveforms when source voltage were unbalance and load current were inductive were gave out. The simulation result shows that UPQC efficiently carry out its compensation function while adopting the proposed control strategy.