Extremum Seeking Control for the Efficiency Optimization of a Multi-stage Converter

The article introduces an extremum seeking control (ESC) technique for determining the optimal operating points of a multi-stage converter named twin-bus buck converter (TBB) [8]. The TBB converter features several modulation parameters, such as the switching frequencies of the CLLC stage and of the TBB post-regulator, which have a notable impact on the overall conversion efficiency. The benefit of off-line optimization techniques is limited due to the difficulties in modeling the converter behavior and the dependence on the actual operating point. Then, a model-free online search method based on the ESC technique is investigated and applied herein to find the optimal switching frequency of the TBB converter stage. The originality of this work lies in the utilization of small frequency perturbations that generate minimal effects on the objective variable, allowing for system optimization. The effectiveness of the proposed search technique is verified through experimental validation using a prototype rated 10 kW.