A Complete Analysis and Implementation of the Single Level Eighteen Step Inverter

This paper proposes a new switching strategy for most-common and well-known three-phase six-step inverter (SSI). In this strategy, each one of the six switches conducts 180-αژ اhere α is the phase delay angle instead of اell-known 180° or 120° conduction modes of SSI. For a Y-connected RL load the output phase voltage becomes a seven-level, eighteen steps waveform, (which is more similar to the sinusoidal waveform in compare with the SSI). In this new strategy 40% reduction of the total harmonic distortion (THD) is achievable and the output lowest harmonic order becomes 11th order rather than 5th. Analysis of the four modes of operation and comparison with the other types of voltage source inverters such as the neutral point clamped (NPC) and the multilevel inverters (MLI) is done. Simulation and experimental results are presented which are verified each other.

Keywords:

voltage source inverters , 180-α° conduction mode , eighteen-step waveform , seven-level inverter , total harmonic distortion and lowest harmonic order