Performance analysis of three-phase PWM AC chopper feeding a delta connected load

Three-phase topology of the bi-directional a.c. controller, comprising power MOSFET embedded four-quadrant switch (4QSW) realizations operating in high-frequency chopping mode is presented. The performance of the controller with balanced, delta-connected, resistive and inductive loads is assessed from the power quality perspective. Gate control logic corresponding to the resistive and inductive loads have been developed. The symmetrical multipulse modulation (SMM) technique is adopted, wherein; several equidistant pulses per half cycle (M) are used. The r.m.s. value of the fundamental component of the output voltage is smoothly varied by varying the duty cycle (δ) of the pulses. It is shown that the lower order harmonics can be substantially reduced by SMM compared to the phase-control scheme, certain harmonics, even being eliminated for certain values of M. Simulated results are presented.