A Novel Improved Performance of Direct Power Control of Unbalanced AC Source

Abstract

Three-phase dc–ac power converters suffer from power oscillation and overcurrent problems in case of the unbal-anced ac source voltage voltage that can be caused by grid/generator faults. Existing solutions to handle these problems are properly selecting and controlling the positive- and negative-sequence currents. In this paper, a new series of control strategies which utilize the zero- sequence components are proposed to enhance the power control ability under this adverse condition. It is concluded that by introducing proper zero-sequence current controls and corresponding circuit configurations, the power converter can enable more flexi-ble control targets, achieving better performances in thedelivered power and the load current when suffering from the unbalanced ac voltage.
Index Terms— Control strategy; dc–ac converter; fault tolerance; unbalanced ac source