Implementation of an Isolated Three-Leg VSC with Star/Hexagon Transformer Based Three-Phase Four-Wire DSTATCOM

A three-phase four-wire DSTATCOM (distribution static compensator) based on three-leg VSC (voltage source converter) isolated with a star/hexagon transformer is demonstrated for power quality enhancement in a three-phase four-wire distribution system. The DSTATCOM is controlled to compensate the reactive power, eliminate harmonic currents, balances the load and also to mitigate the neutral current. The use of star/hexagon transformer for interfacing to a three-phase four-wire power distribution system reduces required rating of the VSC for a three-phase four-wire DSTATCOM. The IGBT (insulated gate bipolar transistor) based VSC is a capacitor supported and it is controlled for the required compensation of the load currents. The dc bus voltage of the VSC is regulated during varying load conditions. The control algorithm is based on the synchronous reference frame (SRF) theory for generating the gating pulses of VSC of DSTATCOM. The performance of the three-phase four-wire DSTATCOM is validated for power quality enhancement with linear loads as well as non-linear loads through hardware implementation using dSPACE, which is based on DS1104 R&D controller and a slave DSP subsystem based on TMS320F240.