Study of Behavior of Voltage and Current Spectra of Three-Level Neutral Point Clamped Converter at Selected Harmonic Elimination Programmed Pulse Pattern Pulse-Width Modulation

The issue of converted voltage distortion by high-power converters at pulse-width modulation (PWM) with a low switching frequency of semiconductor modules is still relevant. Currently, the Programmed Pulse Pattern PWM (PPWM) technique is used extensively that allows pre-eliminating the selected harmonics from the converter’s voltage and current spectrum or reducing them to meet the voltage quality standard requirements. A review of scientific publications has shown the insufficiency of available studies on defining and estimating the impact of powerful converters with PPWM. The problem of defining the amplitudes of higher harmonics generated by a converter with PPWM, which are the main cause of electronic equipment failures at the common grid connection point, is particularly relevant. This study considers the behavior of the NPC converter voltage and current spectra at PPWM with the selected harmonic elimination (SHE) for three-level (3L) voltage waveforms. The behavior of up to the 50th non-eliminated harmonics in the NPC converter voltage and current spectra is first shown for a modulation factor changing within 0–1.15 at the pitch of 0.01 for six different SHE PPWM: no. 1–5 and 7; no. 2–5, 7, 11, and 13; no. 3–5, 7, 11, 13, 17, and 19; no. 4–5, 7, 11, 13, 17, 19, 23, and 25; no. 5–5, 7, 11, 13, 17, 19, 23, 25; 29, and 31; no. 6–5, 7, 11, 13, 17, 19, 23, 25, 29, 31, 35, and 37. The concept proposed herein allows measuring the current consumed amplitudes of NPC converter with SHE PPWM at the low average error of about 6%. The adequacy of the approach used herein to determine the current harmonic amplitudes has been experimentally verified with laboratory equipment. The results are consistent with engineering accuracy. The research work is promising for further study and estimation of the impact of the NPC converter SHE PPWM for more complex multi-pulse grid connection circuits and resonance phenomena.