A simple DC-link balancing controller for a solid-state transformer using cascaded H-bridge rectifiers

Abstract

In this paper, a simple voltage balance controller for a SST using cascaded H-bridge rectifiers is proposed to deal with voltage unbalance problem of DC-links. The tolerance of parameters on DC-DC stage, which consists of parallel-connected DAB converters, can cause the unbalance problem of output voltage on H-bridge rectifiers. In order to solve this unbalance problem, an additional voltage balance controller is merged in conventional output voltage PI controller of DAB converter. By using this proposed voltage balance controller, a modified independent phase-shift angle is applied to each DAB converters. Through this process, the voltage of DC-links and power of DAB converters can be balanced. Compared to the conventional voltage balance methods, the proposed balance controller does not require additional current sensor or other devices. The performance of proposed balance controller is verified by experimental results using a 5kW SST prototype.