Three-phase four-wire DSTATCOM based on a three-dimensional PWM algorithm

A modified voltage space vector pulse-width modulated (PWM) algorithm for three-phase four-wire distribution static compensator (DSTATCOM) is described in this paper. The mathematical model of shunt-connected three-leg inverter in three-phase four-wire system is studied in a-b-c frame. The p-q-o theory based on the instantaneous reactive power theory is applied to detect the reference current. A fast and generalized applicable three-dimensional space vector modulation (3DSVM) is proposed for controlling a three-leg inverter. The reference voltage vector is decomposed into an offset vector and a two-level vector. So identification of neighboring vectors and dwell times calculation are all settled by a general two-level 3DSVM control. This algorithm can also be applied to multilevel inverter. The zero-sequence component of each vector is considered in order to implement the neutral current compensation. The simulation is performed by EMTDC/PSCAD software. The neutral current, harmonics current, unbalance current and reactive current can be compensated. The result shows that the validity of the proposed 3DSVM can be applied to compensate power quality problems in three-phase four-wire system.