Performance Comparison of Single-Phase Multilevel Inverter with SPWM Unipolar and Bipolar Switching Techniques

Sinusoidal Pulse Width Modulation (SPWM) method is one of the Pulse Width Modulation (PWM) switching techniques which is working by comparing the sinusoidal reference signal to a triangular carrier signal. The SPWM switching technique can be implemented using either unipolar or bipolar technique. This paper discusses the performance comparison of 5-level and 7-level single-phase cascade H-bridge multilevel inverters using SPWM unipolar and bipolar switching methods. The study results show that increasing the level of a single-phase multilevel inverter circuit can effectively reduce the harmonic distortion. The SPWM unipolar signal switching technique also produces lower values of Total harmonic Distortion (THD) than the use of bipolar technique. Higher the switching frequency and modulation index used, smaller will be the harmonic distortion.