Simple Fundamental Current Estimation and Smooth Transition Between Synchronous Optimal PWM and Asynchronous SVM

Abstract

In this article, two aspects of a synchronous optimal pulsewidth modulation (SOPWM) strategy for inverter control are considered. First, a fundamental current estimation method is proposed, which eliminates the undesired harmonics in the measured currents and allows us to integrate the SOPWM strategy into a field-oriented control scheme without the need of an observer. The main features of this method are its implementation simplicity and its independence of the load parameters. Second, a smooth transition between asynchronous space vector modulation (SVM) and SOPWM is introduced to avoid performance degradation and overcurrent in the current control loops. The proposed transition strategy transforms the asynchronous SVM into a frequency- and phase-synchronous SVM before the transition to SOPWM takes place. Experimental results for a two-level inverter-fed three-phase inductive load confirm the accurate steady-state and transient performance of the proposed estimation and transition strategies.