Extended Dual Side Asymmetric Phase Shift Modulation and Smooth Mode Transition Method for Dual Active Bridge Converter

Dual active bridge (DAB) converters are widely used in dc microgrids due to their advantages of electrical isolation, wide voltage range operation, and bidirectional power flow. When the voltage conversion ratio is mismatched, the conventional symmetric phase shift modulation method has a narrow zero voltage switching (ZVS) range, low light-load efficiency, and uncontrollable inductor current oscillations caused by abrupt changes in variables during mode switching. In order to solve the above-mentioned problems, an extended dual side asymmetric phase shift modulation (EDAPSM) and smooth mode transition method is proposed in this article. Analytical solutions over the entire power range are derived based on the proposed approximation method. The inherent cause of variable discontinuities during mode transitions is identified, and a novel approach to achieve smooth mode switching is presented, thereby improving the efficiency of the DAB converter over a wide voltage range, particularly under light-load conditions. A 1-kW DAB prototype is constructed, and the modulation method can achieve a maximal efficiency of 98.03%. The experimental results verify the correctness and effectiveness of the method proposed in this article.