This paper first identifies and 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 the following 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 for the first time, 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 that the conventional ESC structure can cause dynamic collapse, corresponding to a 100% output voltage and current drop under a sudden increase in reference power from 25% to 50% of the rated power with resistive loads. In contrast, the proposed EESC structure not only maintains the same efficiency optimization as the conventional ESC but also exhibits only a brief 5% drop in output voltage and current under the same dynamic conditions, immediately recovering and thus avoiding dynamic collapse.
Wu et al. (Thu,) studied this question.