A Simple Carrier-BasedPWM MethodFor Three-PhaseFour-Leg InvertersConsidering All Four PoleVoltages Simultaneously

Complexity ofthethree-dimensional space vector PWM (3D-SVM) algorithm canbereduced using an equivalent carrier-based continuous PWM method. However, since theneutral-phase voltage wasneglected in determining thezero-sequence voltage ofthePWM, it introduces an errorforan imbalance case,increases complexity ofthealgorithm, andisinconsistent withthe carrier-based PWM forthethree-leg inverter. Thispaper proposes anewandnatural standpoint forthecarrier-based PWM ofthefour-leg inverter, by considering allpole voltages including thatoftheneutral phasesimultaneously inthedetermination ofzero-sequence voltage. Thisnew viewpoint renders thefullconsistency betweenthePWM methodsforthethree-andfour-leg inverters. Itcan generate bothcontinuous anddiscontinuous PWM easily in thesamemannerasisdoneforthethree-leg inverter. The connection betweenthediscontinuous PWM andthe3D- SVM isalsoclarified. IndexTerms-Carrier-based PWM, four-leg inverters, zero-sequence voltage, discontinuous PWM, three- dimensional space vector PWM.

[1]  D. Boroyevich,et al.  An Alternative Approach on Three-Dimensional Space-Vector Modulation of Three-Phase Inverters , 2005, 2005 IEEE 36th Power Electronics Specialists Conference.

[2]  M.P. Kazmierkowski,et al.  Current regulation of four-leg PWM/VSI , 1998, IECON '98. Proceedings of the 24th Annual Conference of the IEEE Industrial Electronics Society (Cat. No.98CH36200).