Hybrid Modulation for Dual Active Bridge Bi-Directional Converter With Extended Power Range For Ultracapacitor Application

In order to actively control the power flow between the load and ultracapacitor, a dual active bridge (DAB) converter can be utilized. Conventional phase shift modulation has difficulties in working with a wide range of source voltage levels and load power levels. In addition, traditional PI controller does not provide satisfactory behavior as the relation between the control variable and output voltage is nonlinear. In this paper, a hybrid modulation scheme is proposed to extend the power range of operation to 100% to 16.67% instead of 100% to 58.33% that is achieved by conventional phase shift modulation. A feedback linearized controller is also designed to achieve a better dynamic response under various load. The detail modulation principle and controller design is given and the experimental results verify the proposed modulation and control scheme.