Performance Evaluation of Real Time Implementation of New Hybrid PWM Strategies for Single Phase Seven Level Asymmetrical Inverter

摘要

Carrier Based Pulse Width Modulation (CBPWM) techniques have been used widely for switching of multilevel inverters due to simplicity and reduced computational requirements than the Space Vector Modulation (SVM). New hybrid carrier based PWM strategies have been implemented for a prototype of single phase seven level asymmetrical inverter in this work. Two inverter bridge circuits are used to achieve seven level output voltage. Phase Disposition (PD), Phase Opposition Disposition (POD), Alternate Phase Opposition Disposition (APOD) and Carrier Overlapping (CO) PWM strategies are used with triangular carriers above zero axis and rectified sine carriers below zero axis along with stepped reference. The triggering pulses are generated using the dSPACE dS1103/Real Time Interface (RTI) hardware and front end tool control desk with MATLAB-SIMULINK environment. The performance indices used are Total Harmonic Distortion (THD), Form factor (FF), Distortion Factor (DF), Root Mean Square (RMS) output voltage. It is observed that COPWM provides relatively better DC bus utilization and relatively lesser harmonic distortion for modulation index m_a=0.7-1.