Enhanced Extremum Seeking Control (EESC) Structure for Dual Bridge DC-DC Converters

This paper analyzes the phenomenon of output voltage collapse under step load perturbations in dual bridge converters where an extremum seeking control (ESC) optimization algorithm is employed. Although ESC is an effective online duty-cycle optimization method under steady-state power transfer conditions, it can result in severe output voltage degradation during large-signal transients. This degradation is primarily caused by two factors: the reduced power transfer capability associated with the optimized duty-cycles, and the limited dynamic capability of the ESC structure to rapidly adjust the duty-cycles. To overcome this limitation, an enhanced extremum seeking control (EESC) structure is proposed, which enables fast output voltage reference tracking under dynamic operating conditions, while preserving ESC’s capability for online duty-cycle optimization to minimize losses and improve efficiency. The proposed method extends the applicability of ESC from steady-state optimization to large-signal dynamic scenarios. Comparative experimental results on a dual active half-bridge (DAHB) converter reveal the output voltage collapse associated with conventional ESC structure and verify the high efficiency and absence of dynamic voltage collapse achieved by the proposed EESC structure.