OPTIMAL PULSEWIDTH MODULATION FOR AC SERVOS AND LOW-COST INDUSTRIAL DRIVES

An optimal pulsewidth modulation method is described in which the dura tions of switching subcycles are considered as optimization variables, a subcycle being the time sequence of three consecutive switching sta te vectors. Operation at variable subcycle duration entails a predicti on of the controlling reference voltage vector. It is a special advant age that the optimization and prediction can be carried out off line. The optimal technique exhibits high dynamic performance. It can be use d for synchronized and asynchronous modulation in a wide range of swit ching frequencies. The optimization reduces the harmonic currents at a given switching frequency. The Fourier spectrum lacks dominant carrie r frequencies. Hardware implementation cost compares with existing non optimal modulation methods.