Evaluation of p.w.m. inverter schemes

The paper surveys the various pulse-width-modulation schemes used in thyristorised inverters. The practical problem of choosing the two variables, frequency-modulation index M and depth of modulation ¿, which determines the output waveshape of the p.w.m. inverter, is also discussed. An algorithm is given to select the values of M and ¿ to obtain minimum low-order harmonics. Some sample results for various cases have been tabulated. The algorithm can be used to extend the range of variables to other values of practical interest. The results so obtained will be of use to a designer in evaluating the various p.w.m. schemes that are feasible.