Effect of Inverter Voltage Levels on Torque Ripples of PMSM Drive

Abstract

This paper investigates the performance of Permanent Magnet Synchronous Motors (PMSM) in terms of torque ripples, a critical aspect affecting their operational efficiency and stability. Torque ripples in AC motors are primarily attributed to the switching action of the inverter Insulated Gate Bipolar Transistors (IGBTs), resulting in current fluctuations that directly influence motor torque. Mitigating these ripples is crucial for enhancing motor performance and reducing mechanical stress. This study focuses on utilizing multilevel inverters to minimize torque ripples by smoothing the motor current through harmonic elimination. Three different types of inverters, namely 2-level, 3-level, and 5-level inverters, are simulated to assess their impact on torque ripple reduction. The torque ripples were obtained from two methods where direct simulation is a method chosen and in second method, the average torque is subtracted from instantaneous torque samples. Stator currents are analyzed in the alpha-beta frame to evaluate the effectiveness of each inverter configuration in producing smoother current profiles and subsequently reducing torque ripples. Additionally, simulations are conducted under varying load torque conditions to assess the robustness and applicability of the proposed methodology across a wide range of operating conditions.

Keywords

• total harmonic distortions (thd)
• modulation index
• switching frequency
• sine pulse width modulation