Research on characteristic and DC voltage balancing control of a novel three-phase line-voltage cascaded unity power factor rectifier under unbalanced grid

Abstract

According to the operating modes of three-phase line-voltage cascaded boost high power factor rectifier topology, the operating characteristics of the rectified output voltage of each module and the characteristics of the topology for automatically balancing the input current under the unbalanced grid are analyzed in this article. Based on the analysis to the unique feature, a simple dual-loop PI control strategy in the rotating coordinate system is designed with no need to deal with the negative sequence component of grid voltage. In response to the issue of unbalanced DC-link capacitor voltage of each module caused by unbalanced grid, injection of the zero-sequence voltage component is adopted in the designed control system, which make the output power of each module be able to be independently regulated, so that the balancing control to the DC-link capacitor voltage of each module is realized. At the same time, the three-phase input currents always remain in balance automatically operating under unity power factor. Simulations and experiments have verified the superiority of the topology structure and the feasibility of the control strategy.