Control and optimization of VCVS static var generators for voltage unbalance mitigation

Reactive power control through static var generator (SVG) has been gaining wide attentions due to its outstanding performance. But for a SVG with traditional control strategies, unbalanced utility voltages have greatly affect the performance of the SVG and in severe case may even cause shut-down of the SVG for overcurrent protection. This paper proposes a voltage controlled voltage source (VCVS) strategy to assure normal operation of SVG with series-connected IGBTs when severe system voltage unbalance happens, and furthermore to mitigate voltage unbalance at the point of common coupling (PCC) whether it is caused by utility or load. The control law, operation principle, compensation characteristics and parameter optimization of the proposed control strategy are analyzed in detail. Based on the VCVS control, a modified VCVS strategy is proposed and the difference between them is presented. Finally, the simulation and experimental investigations were carried out respectively for resistive and rectifier load conditions. The results verified that the current passes through the SVG is under control and the voltage at PCC is much more balanced than that before compensation. The compensation performance of the SVG is thus proved satisfactory