Abstract

Two hybrid PWM methods are proposed in this paper for a pump drive based on three-level Neutral-Point Clamped (NPC) inverter. The envisaged PWM methods are aimed at reducing output voltage harmonic distortion. While the first PWM method incorporates suitable voltage injection to the carrier signals, the second PWM method incorporates voltage injection to both carrier and the modulating signals for controlling the NPC drive. Detailed harmonic analysis is presented using Double Fourier Integral Approach (DFIA) for both the hybrid PWM methods by separately identifying their basic unit cells, their boundaries that demarcates different regions of inverter drive. Complete analytical expressions for dc, fundamental, carrier and side-band harmonic components present in the output voltage of the NPC drive are presented for both the hybrid PWM methods. The proposed PWM methods are simulated using Matlab/Simulink and are experimentally validated using an induction motor driven pump load, following V/f control. Superiority of the hybrid PWM methods in comparison to the existing PWM methods are demonstrated with v_THD , weighted THD (v_WTHD ), i_THD , harmonic loss factor etc., supporting the envisaged PWM methods.

摘要

针对基于三电平中性点钳位（NPC）逆变器的泵驱动，本文提出了两种混合PWM方法。设想的PWM方法旨在减少输出电压谐波失真。第一种PWM方法将适当的电压注入并入载波信号，而第二种PWM方法将电压注入并入载波和调制信号，以控制NPC驱动器。对于这两种混合PWM方法，使用双傅立叶积分方法（DFIA）进行了详细的谐波分析，方法是分别识别其基本单位单元以及划分变频器驱动器不同区域的边界，从而确定两种基本方法。两种混合PWM方法都给出了NPC驱动器输出电压中存在的直流，基波，载波和边带谐波分量的完整解析表达式。提出的PWM方法使用Matlab / Simulink进行了仿真，并在V / f控制下使用感应电动机驱动的泵负载进行了实验验证。与现有的PWM方法相比，混合PWM方法具有以下优势：v _THD ，加权THD（v _WTHD ），i _THD ，谐波损耗因子等，支持设想的PWM方法。