State Trajectory Based Feedforward Control for Phase Shift Modulated LLC Resonant Converter

The LLC resonant converter can be utilized in the new energy vessel power systems, connecting new energy sources and power batteries or daily loads. Employing a phase shift modulation (PSM) strategy instead of pulse frequency modulation (PFM) strategy can enhance the utilization of magnetic components and improve the power density of the converter. However, the new energy vessel power systems face the challenge of rapidly fluctuating and unpredictable propulsion loads, necessitating the LLC resonant converter to possess a swift dynamic response capability. To improve the dynamic response of a phase shift modulated LLC resonant converter, this work proposes a state trajectory based feedforward control (STFFC) strategy. The phase shift ratio under a specific load is approximately estimated through the geometric relationships of the state trajectory, and this ratio is then fed forward to the output of a traditional PI controller. The validation results show that by utilizing the proposed STFFC strategy, the transient switching paths of state trajectories are significantly simplified, and both overshoot ratios and settling times are substantially reduced.