A Simple Three-phase Three-wire Voltage Disturbance Compensator

The two-leg four-switch VC-VSI with a direct load voltage controller has been developed as a three-phase multi- functional voltage disturbance compensator for a three-phase three-wire system. By controlling only two legs (two phases) of the inverter, the third leg automatically generates the correct third voltage. The VC-VSI is connected in series between the PCC and loads by three single-phase matching transformers. The transformer primary windings are connected in delta. The VC- VSI operates to directly control the load voltage rather than its output voltage using a simple PI controller. The VC-VSI is able to produce automatically a three-phase compensation voltage so that the load voltage is sinusoidal, symmetrical and constant at a nominal value. Computer simulation verifies that the VC-VSI is able to perform well as a voltage disturbance compensator, although there is still an insignificant deviation (around 1%). The THD of the load voltage reduces to 1.4%.