Application of SVPWM Technique to Three Level Voltage Source Inverter

摘要

The purpose of the study is to compute the Total Harmonic Distortion (THD) with the proposed latest Space Vector Pulse Width Modulation(SVPWM) technique and prove that the proposed technique gives lesser THD compared to that of Sinusoidal PWM.Multilevel inversion is a power conversion strategy in which the output voltage is obtained in steps thus bringing the output closer to a sine wave and reduces the Total Harmonic Distortion (THD). Multilevel inverter structures have been developed to overcome shortcomings in solid-state switching device ratings so that they can be applied to higher voltage systems. The multilevel Voltage Source Inverter (VSI) unique structure allows them to reach high voltages with low harmonics without the use of transformers. The general function of the multilevel inverter is to synthesize a desired ac voltage from several levels of dc voltages. In recent years, the multilevel inverters have drawn tremendous interest in the area of high-power medium-voltage energy control. Three different topologies have been proposed for multilevel inverters like Diode-Clamped Inverter (DCI), Capacitor Clamped Inverter (CCI) and Cascaded Multicell Inverter (CMI). The DCI is also called the Neutral-Point Clamped (NPC) inverter, when it was first used in a three-level inverter in which the mid-voltage level was defined as the neutral point. CCI is also called Flying Capacitor Inverter (FCI) and cascaded multicell is combination of individual small voltage sources, with separated dc sources. In addition, several modulation and control strategies have been developed or adopted for multilevel inverters including multilevel Sinusoidal Pulse Width Modulation (SPWM), and Space Vector Modulation (SVM).