PWM Sequence Selection and Optimization: A Novel Approach

A variety of means have been used in the past for assessing the quality of pulsewidth modulated (PWM) inverter output voltages. A further analysis is given of the performance of such voltage sequences. The analysis is primarily computer-based, but experimental data are also included. In this case the discussion is clarified by the introduction of a new performance measure, based on the crest factor of the current waveform induced by the sequence. The use of this measure as an index for the construction of optimized sequences is proposed and illustrated. Some consideration is also given to the selection of the most suitable switching frequency for the inverter. The text relates directly to inverters intended for use in induction machine drives, and the sequences used as examples herein are generated using the ``subharmonic'' or ``triangulation'' approach. Much of the analysis is, however, relevant to sequences generated using other modulation methods.