Online EIS Evaluation of PEM Electrolyzer Powered by LLC Resonant Converter

Aiming at the online evaluation of the performance of electrolyzers in renewable energy hydrogen production systems, especially the performance analysis of the impendence spectrum of the electrolyzer. This paper proposes an EIS testing scheme for a PEM electrolyzer powered by a full bridge LLC resonator converter based on analyzing the test method of adding sinusoidal signals of different frequencies on stable DC power. A collaborative control strategy of inversion-rectification is proposed for LLC converter, which includes frequency control of the pre-stage circuit for stable DC power of electrolyzer and PWM rectification control of the post-stage circuit for superimposing disturbance signals of different frequencies. Triangular wave signals of different frequencies are superimposed on the input voltage of the electrolytic cell through LLC converter, and the impedance characteristics under different harmonics are obtained through FFT to evaluate the impedance spectrum of the electrolyzer. The simulation results show that the evaluation of EIS results in this paper basically conforms to the theoretical values, and the EIS online evaluation function of the electrolyzer has been achieved.