Soft-sensing Research Of Proton Exchange Membrane Water Content Based On Impedance Test

Proton exchange membrane fuel cell (PEMFC) received a large number of concerns and attention of the researchers, because of its advantages such as clean pollution-free (products for water), high energy conversion efficiency (actual efficiency of 40%～60%), high energy density, and so on, it become a new energy research hotspot. PEMFC related to multi-disciplinary knowledge, sucha s fluid kinematics, electrochemistry, materials science, automatic control, and so on. Many experimentation and literature shows that the protons in the membrane transfer in the form of hydrated proton, water is the carrier of the proton conduction, water content of PEM is largely decided by the size of the electrical conductivity, suitable water content can achieve the best electrical conductivity, water content is too high and too low will lower the conductivity, thus reducing the generating efficiency. Water content can indirectly got by measuring the relative humidityt, but its fuel cell technology relative humidity testing complex, large expensive equipment, can be designed only to test the application of the research phase, can not be used for running the site. PEM water power reactor by measuring the relative humidity has been indirect, but its relative humidity test need complicated technically, large and expensive equipment, only can be used as test application of the design and research stage, can not be used for site monitoring. In this paper, a PEM water content of soft-sensing technique is introduced, in order to solve the PEM water site monitoring and control.In order to carry out soft-sensor of PEM water content ,we must determine the relevant variables of the model and obtain relevant data that needed by learning and training, in which fuel cell's single-chip ohmic resistance, voltage, temperature are the most important data, and there haven't ready-made, simple test instruments and equipment. This paper summarizes the analysis of theory and practice of knowledge both at home and abroad, introduces a PEMFC single-chip ohmic resistance online testing device to obtain these key data.This paper introduce PEM water transmission three ways which appears in a variety of state and the transmission process, there are electromigration, stress migration, proliferation of concentration, and establish their mathematical model. This article describes their mathematical model and analysis the impact of PEM water content by the main factors. We established the mechanism model of PEM water content based on these theoretical analysis.According requirements of soft-sensor design, we select BP neural network as a modeling method, study the methods of data acquisition and pre-treatment, determine the relevant parameters and the transfer function type of BP neural network, implement soft-sensor method, then training and correction this model. The final verify results show that the soft-sensing method to achieve the measurement of PEM water content,it is the correct and effective.