Overmodulation of seven-phase systems using minimum infinity norm

Abstract

This paper introduces a new approach to pulse width modulation for multi-phase converters. It is presented a carrier based PWM algorithm for seven phase converters with modified calculation of modulation signals. They are calculated by minimum infinity norm method. The proposed algorithm allows selection of arbitrary degrees of freedom which enables transition and operation in overmodulation area with higher modulation index while ensuring the maximum utilization of a dc-link voltage. It is shown that the proposed method is very straightforward with calculation demands comparable to the multi-phase space vector PWM, and furthermore, it is possible easily to modify the proposed algorithm for converters with different number of phases. The proposed algorithm is compared to space vector pulse width modulation and it is verified by extensive simulation study as well as by experiments on a laboratory prototype.