Generalized Three-Level Optimal Pulse Patterns With Lower Harmonic Distortion

Optimized pulse patterns (OPPs) minimize the harmonic distortions of inductive loads. To simplify the analysis and computation, quarter- and half-wave symmetry is typically imposed. Moreover, for three-level converters, the switch positions are required to be non-negative in the positive half-wave of the fundamental period. This article investigates the impact of these restrictions on the harmonic distortions. By relaxing the symmetry requirements and by allowing also negative switch positions in the positive half-wave of the fundamental period, the current distortions can be reduced by up to one-third compared to the traditional OPP formulation.