Abstract
This paper addresses calculation of current Total Harmonic Distortion (THD) for a single-phase multilevel PWM inverter with LCL-filter. Analytical approach introduced in late 1980s for a 2-level inverter with inductance dominated load is generalized for a single-phase multilevel inverter with an arbitrary number of voltage levels accounting for the smoothing effect of LCL-filter. Though the obtained closed-form analytical solutions initially assume (infinitely) large ratio of switching and fundamental frequencies, they are practically accurate for the ratios of (apparent) switching and fundamental frequencies larger than 25–30. Also suggested are simple accurate Bessel function approximations. The formulas clearly reveal a single-phase PWM inverter current THD dependence on LCL-filter parameters and modulation index for an arbitrary level count and are easily modified to cover a grid-connected case.
Published Version
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