An instantaneous value voltage control ac chopper for compensating voltage sag in three phase four wire system

The aim of this paper is to present the application of three cells of a single phase ac-chopper interfacing with series injection transformer for compensating voltage sag in three phase four wire system. Each ac-chopper cell is independently controlled by instantaneous value voltage control technique. This technique is a comparison between the sinusoidal reference signal and the active triangle signal. The sinusoidal reference signal is calculated by using the d-q reference fame from the difference between a desired voltage and a source voltage, and the active triangle is spontaneously amplitude adjusted via a voltage sag level. Thereupon, with this proposed technique, the ac chopper can rapidly compensate the related voltage sag and provide constant output voltages. Positive sequence PLL is applied to generate angle velocity (ω); thus, the proposed ac chopper can perform both balance and unbalance voltage sag. To confirm the proposed application, the simulation model of a voltage feedback control system with current disturbance cancellation using MATLAB/Simulink is performed and the simulation results are analyzed.