An Improved Space Vector Pulse Width Modulation for Nine-Level Asymmetric Cascaded H-Bridge Three-Phase Inverter

Abstract

This paper presents an improved space vector pulse width modulation (SVPWM) for nine-level cascaded H-bridge inverter with unequal DC voltage sources. This technique is based on the use of $$60^{\circ }$$ spaced r–s coordinate system to achieve SVPWM of multilevel three-phase inverter. In order to realize nine-level inverter, conventional SVPWM requires 1296 lookup tables, which is difficult to realize in the form of lookup tables, but the proposed technique does not require any lookup tables in the process of SVPWM realization, and it is generalized algorithm for any inverter levels. Hence, the system memory requirement is very less. The proposed modulation technique improves the nature of inverter output voltage and its total harmonic distortion value. Simulation results have been carried out using MATLAB/SIMULINK software tool. A comparative analysis is performed with classical pulse width modulation (PWM) techniques like sinusoidal PWM and third harmonic injection PWM at different modulation indices. To validate the simulation results and to confirm the practicality of the proposed control algorithm, experimental verification has been done.