A derivative-free method to develop optimal PWM strategies in power converters

The authors have previously described a minimization procedure able to optimize any cost function in PWM (pulse width modulation) inverters without computing derivatives. As a consequence, CAD (computer-aided design) modules have been developed to obtain optimal PWM strategies. Results were obtained as look-up tables of switching angles used by the control microprocessor. The authors describe the optimization procedure and show some examples of switching angle variation versus rotor resistance. The simulation of various working conditions shows that parameter variations have little effect on optimization process results. As a consequence, it is possible to save RAM space by using a reduced number of look-up tables, without a large spread about the optimum