Aiming at the three major challenges of DC bias construction

low high-frequency excitation efficiency

and poor voltage monitoring accuracy in the measurement of wideband impedance of megawatt-level proton exchange membrane electrolyzers

we propose a hybrid excitation topology and adaptive sliding mode observation method based on supercapacitor coupling. Traditional linear excitation power supplies have inefficiencies in high-power applications

and switching power supply solutions face bottlenecks where DC bias and broadband excitation (0.1 Hz~10 kHz) are incompatible. Through the equipotential coupling of supercapacitors and DC busbars

the following can be realized: 1. Adaptive establishment of high-voltage DC bias to replace expensive DC/DC modules; 2. The full-bridge inverter adopts peak current-unipolar frequency multiplier compound control

which significantly improves the excitation efficiency of 200 Hz~10 kHz. Aiming at the problem of capacitance voltage monitoring caused by high-frequency ripple

we propose an improved sliding mode observer: the state observation equation is constructed by modeling the high-frequency equivalent circuit

and the adaptive approach law with phase compensation is used to suppress the switching noise interference

which effectively solves the problem of accuracy deterioration of traditional voltage sensors in high-frequency measurement. Experimental verification shows that the proposed scheme can meet the requirements of accurate measurement of wide-frequency impedance of high-power proton exchange membrane electrolyzers

and greatly reduce the system complexity and implementation cost. This study provides an engineering solution for high-voltage electrolysis hydrogen production system with both broadband excitation ability and online monitoring accuracy.