H2 purity control of high-pressure alkaline electrolyzers

Abstract

This paper proposes a control strategy that mitigates the cross contamination of H2 and O2 in a high-pressure alkaline electrolyzer, which consequently increases the supplied gases purity. In order to reduce the diffusion of gases through the membrane, the controller establishes the opening of two outlet valves based on the pressure of the system and the difference in liquid level between both separation chambers. Therefore, a multiple input - multiple output optimal controller is designed here. For this purpose, an available high-fidelity model was simplified in order to obtain a control-oriented model. The proposed controller was evaluated in simulation using the high-fidelity nonlinear model in a wide operating range and was compared with a pair of decoupled PI controllers. The resulting impurity of gases was below 1% in all cases.