Investigation for power quality in a PWM AC controller feeding a 3-phase 3-wire wye load

Single- and three-phase topologies of the bi-directional a.c. controller, comprising power MOSFET embedded four-quadrant switch (4QSW) realizations operating in high-frequency chopping mode are presented. The performance of the controller with inductive load is assessed for power quality. A three-phase, three-wire, wye-connected inductive load is considered and the corresponding gate controls has been developed. The symmetrical multipulse modulation (SMM) technique is adopted, wherein; 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, certain harmonics, even being eliminated for certain values of M. Simulated results are presented for both topologies, and, experimental results are also furnished for the single-phase one.