Improved Modulation Strategy Using Dual Phase Shift Modulation for Active Commutated Current-Fed Dual Active Bridge

This paper proposes dual phase shift modulation (DPSM) for active commutated current-fed dual active bridge for low-voltage (LV) high-power application to improve the performance of the converter at light loads. The proposed DPSM uses an additional control variable to actively control the peak current in the converter that helps to improve the performance as compared to simpler single variable but unregulated peak current control, phase shift modulation (PSM). The control variables are chosen such that the excess current is just enough to achieve zero current switching (ZCS) turn-off of the LV devices. In the reverse direction, the converter is a full-bridge converter with LC filter. The implementation of the conventional PSM to the full bridge, popularly known as phase-shift full bridge is simple but restricted by the zero voltage switching (ZVS) range. The proposed DPSM is implemented in the reverse direction to maintain the ZVS turn-on of the high-voltage (HV) devices even at very light loads by utilizing the LV devices instead of using them only for synchronous rectification. At higher loads where achieving ZVS is relatively easy, the modulation shifts to conventional PSM to reduce the circulating current and the associated duty cycle loss. The improvement in the performance is validated experimentally with a 1-kW prototype developed for a 30% variation in the LV voltage (42-56 V) for both directions of operation. The control of the peak current improved the efficiency by 12% from the conventional PSM at 10% load at the highest current (42 V) in the forward operation. In the reverse direction, the ZVS turn-on for the HV devices is achieved even at 6% load by the proposed modulation at the highest voltage (56 V). Thus, the proposed DPSM is a software-only solution that does not require any additional active or passive components, offering an improved performance while maintaining a low component count and simplicity of the power electronics circuit.