SVPWM-Based Power Control Strategy for a Three-Port Four-Leg DC/AC Converter With Enhanced Power Transfer Mode

The single-stage T-type three-port converter enables efficient and accurate power distribution between two dc ports and one ac port without embedding an auxiliary dc/dc converter. Considering the diversity of loads, this article adds a T-type fourth leg to efficiently handle asymmetric and nonlinear loads. Accordingly, a new simplified space vector modulation strategy suitable for the asymmetric vector space is proposed. Only eight special switching states are used to compose the reference vector. Then, a unified algorithm is presented to obtain the maximum power distribution range of the dc port for both the T-type three-leg and four-leg three-port converters. Besides, to reduce the limitation on the dc port power transfer from the light loads, a novel technique based on the zero-sequence current is proposed to significantly expand the power distribution range. This method leverages the zero-sequence loop provided by the basic filtering components to generate additional converter currents that are crucial for the power distribution. The effectiveness of the newly proposed strategies is convincingly demonstrated through tests conducted on a 3-kW prototype.