Continuous Phase-Shifted Selective Harmonic Elimination and DC-Link Voltage Balance Solution for H-bridge Multilevel Configurations, Applied to 5L HNPC

Abstract

This paper proposes a method for calculating selective harmonic elimination (SHE) angle solutions applied to multilevel voltage waveforms (of more than three levels of voltage): Phase-shifted SHE (PS-SHE). This technique is based on the calculation of simple SHE angles, increasing the number of levels and minimized harmonics by means of phase shift application. Compared to classical calculation, continuous SHE solution can be achieved for the whole modulation index range. Added to this, dc-link voltages balancing strategy is proposed for converters based on single-phase H-bridge (HB) configurations with multilevel (more than two levels) arms, using SHE. It is based on a prediction of the neutral point current and a hysteresis band. This strategy does not increase the number of commutations and shares them equally among the arms inside the HB. The good performance of the two proposed techniques (PS-SHE and dc-link neutral point regulation strategy) are proven into a downscaled five-level HB neutral-point-clamped (5L HNPC) converter topology. The carried out tests prove the suitability of the proposed techniques.