Rapid Estimation Technology of Fuel Cell Internal State Based on Single Frequency Impedance Phase Angle Measurement: A Case Study

Improper internal states in proton exchange membrane fuel cells (PEMFCs), such as insufficient reactant concentration, lower membrane water content, and excessive liquid water, will lead to significant reductions in durability and reliability, which is a bottleneck restricting the large-scale commercial application of the PEMFC system. Closed-loop management with internal state feedback is regarded as a promising strategy for prolonging its lifespan and enhancing its reliability. The key issue for the closed-loop management strategy is how to estimate the internal operating state of the PEMFC stack accurately and quickly. Consequently, an estimation method of stack internal operating states based on the medium frequency impedance phase angle measurement, which has the characteristics of short acquisition time, small measurement error, and high resolution, is proposed in this paper. The sensitivity, monotonicity, correlation analysis in the steady state, and response characteristics analysis in the dynamic state show that the proposed method is effective, competent, and qualified for internal state estimation. Then, the estimated internal state is applied to the system’s closed-loop management as feedback. The experiment results show that the PEMFC can be maintained at the expected state and that improper states will be avoided. The proposed estimation technology will significantly facilitate the system’s closed-loop management, thereby enhancing the reliability and durability of PEMFCs.