NVH characterization of new PWM strategies

Pulse Width Modulation (PWM) technique is widely used to drive AC machines at variable speed, however it generates high frequency harmonics which degrade sound quality. In the last decades, different PWM strategies have been designed to limit switching loss, and/or harmonic generation. Among them, discontinuous strategies are based on the injection of a zero-sequence signal, that strongly impacts the resulting voltage spectrum. An analytic formulation of the zero-sequence signal is proposed by the authors. It allows the creation of new PWM strategies, that can be easily experimented. In this paper, a preliminary study is performed with six new PWM strategies based on this analytic formulation. They are implemented on a basic test bench to perform a NVH characterization. Sound quality metrics are used to qualify the sound signature they produce. The resulting SPL is comparable with that of existing strategies, however their timbre is different in terms of low-frequency content and rattling.