Power quality assessment in a bi-directional AC/AC converter with four-quadrant switch realizations

Single-phase 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 resistive load is assessed from the power quality perspective. A three-phase three-wire resistive load is considered for the three-phase topology and the corresponding gate control logic has 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 (d) 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 for both topologies, and, experimental results are also furnished for the single-phase one.