Optimal pulsewidth modulation of multilevel inverters for low switching frequency control of medium voltage high power industrial AC drives

This paper presents an optimal pulsewidth modulation (PWM) technique for low switching frequency control of multilevel inverters for medium voltage high power industrial AC drives applications. Synchronous optimal PWM permits setting the maximum switching frequency to a low value without compromising in THD. Low switching frequency reduces the switching losses of the power semiconductor devices, resulting in higher inverter power output and efficiency. Experimental results of a five-level inverter drive using optimal PWM are presented. Two types of topologies are discussed: 1) Isolated dc link topology and 2) Common dc link topology with common mode inductor.