Adapted NSPWM for Single DC-Link Dual-Inverter Fed Open-End Motor With Negligible Low-Order Harmonics and Efficiency Enhancement

In this paper, the near-state pulsewidth modulation (NSPWM), adapted to be implemented in dual-voltage-source inverter (VSI) fed open-end motor, is proposed with the aim of mitigating low-order harmonics (which lead to current total harmonic distortion (THD) minimization). The following two proposed methods are studied in detail: 1) fixing phase angle displacement (PAD) between two VSIs to 120° while adjusting the modulation index (MI); and 2) fixing MI to the predetermined value (wherein low-order harmonics are highly mitigated) while adjusting PAD. Furthermore, the proposed approaches enhance efficiency by limiting the number of commutations within the switching interval. The paper also presents the mathematical approaches to accurately determine low-order harmonic components and switching losses for dual-VSI structure. The experimental setup, including dual-VSI and open-end induction motor, is assembled in the laboratory to evaluate performance of the proposed method. Finally, the simulation results, carried out in the MATLAB/Simulink environment, are found to be in close agreement with experimental data.

I. Introduction

Due to global warming worries, higher efficiency acquisitiveness, and soaring of the fuel price, hybrid electric vehicles (HEVs) have recently attracted more attention over internal combustion engine (ICE) [1], [2]. Thanks to the modern hardware/controlling technology, these novel vehicles are expected to become common transport in the near future. Conventionally, these vehicles preferably use low dc-voltage level to account for battery safety/efficiency concerns [2]. Hence, a dc–dc converter, followed by a voltage-source inverter (VSI) stage, is designed to boost dc-link voltage level approximately by a factor of 2 (i.e., in Toyota Prius). Therefore, the total efficiency is further deteriorated due to the presence of huge passive components.