Hybrid Control Scheme for Three-Phase Multilevel Unidirectional Rectifier Under Unbalanced Input Voltages

Abstract

In this paper, a hybrid control scheme for three-phase Y-connected multilevel bridgeless rectifier (TMBR) under unbalanced input voltages is presented, based on the mathematical model of the TMBR topology, with the emphasis on the discussion for power fluctuation suppression, dc-link capacitor voltages balancing and input current zero-crossing distortion elimination. With the hybrid control scheme, the power fluctuation can be suppressed and three-phase input currents can flow with a purely sinusoidal waveform, besides, three-phase dc-link capacitor voltages can be controlled to be equal to each other under unbalanced input voltages. Moreover, the proposed hybrid control scheme is applicable to all other three-phase three wire multilevel unidirectional rectifiers under unbalanced input voltages. The validity of the proposed control scheme is demonstrated by the mathematical deduction. The simulations and experimental results verify that, with the proposed control scheme, TMBR can stably operate not only under balanced input voltages but also under unbalanced input voltages.