NOVEL ANALYTICAL STUDY OF DISTORTION MINIMIZATION PWM.

In pulsewidth modulated inverters for induction motor drives it has been shown that the distortion minimization modulation strategy offers the possibility of optimum inverter and motor performance in the critical transition region up to the familiar six-step waveform. The study of this technique, however, relies upon complex and time-consuming multivariable search techniques and methods must be found to reduce the problem to a form more suited to computer analysis. A new, direct analytical approach to the distortion minimization strategy is presented, which simplifies the evaluation of the optimum switching angles for any number of switchings per cycle and for a given value of fundamental voltage. Among the principal advantages of this technique are its simplicity, accuracy, ease of computer implementation and the fact that it does not require the evaluation of long Fourier series. It is also a purely analytical approach and it is directly applicable to both single-phase and three-phase systems. A digital modulator which is capable of implementing these optimum waveforms is presented. This modulator is designed to have very fast transient response with zero phase shift.