Study of harmonic elimination technology for multi-level inverters

Multi-level converters as a novel kind of converters used in high voltage and high power application field, can generate near sinusoidal voltages with only fundamental frequency switching; and have almost no electromagnetic interference or common-mode voltage. This paper introduces an multi-level inverter SHEPWM technique based on Walsh transform, and analyzes the models of multi-level inverter PWM output waveforms. Using the Walsh function waveform analytic technique, the multi-level inverter´s switching angles are optimized by solving linear algebraic equations instead of solving nonlinear transcendental equations. By searching all feasible initial conditions, the solutions are the piecewise linear equations with the fundamental amplitude. The problem of on-line solving the multi-level inverter´s switching angles is resolved by the piecewise linear equations. Finally, The simulation and experimental results verify the precise, practicality and feasibility of multi-level inverter based on Walsh functions.