Study on Three-phase Four-wire Wiring D-statcom Control Mode Based on Instantaneous Symmetrical Components Mthod

One of the main reasons causing unbalance wave of three-phase current and voltage in three-phase four-wire distribution grid is the three-phase unbalance load. This paper proposes a new control method of positive sequence, negative sequence and zero sequence direct current control based on the Instantaneous Symmetrical Components which can decompose the three-phase current and voltage into sequence components. The control method is used in the distribution grid which parallel with D-STATCOM to make three-phase current symmetry at grid side. The positive sequence current control is used to control the D-STATCOM to generate the three-phase positive sequence current that gird required. In order to maintain the three-phase current balance, negative sequence and zero sequence current should be transformed from the ABC coordinate system to the DQO synchronous rotating coordinate system and subtract with expected value 0. Simulation results are presented to verify the validity of the proposed control strategy. It can not only inhibit three-phase unbalance current, but also filter out high frequency harmonics in the distribution grid.