Development of Online Fuel Cell High Frequency Resistance Monitor Controller 2020-01-1177
Proton exchange membrane fuel cell (PEMFC) system is expected to be the next generation vehicle powertrain. However, water management is still the main problem which directly effects the performance, reliability and durability in PEMFC system. To ensure the accurate water content estimation, High Frequency Resistance (HFR) is the most representative indicator in laboratory. The HFR is calculated by detecting the AC voltage response of fuel cell under the excitation of 1kHZ AC current. In general, a AC voltage about 5mV should be measured accurately at a DC voltage of 0.6V-1V. So, online HFR monitor is a big challenge for vehicle application, due to its low Signal/Noise (S/N) ratio, poor EMC environment, high common mode voltage and numerous cells. In this work, an online fuel cell HFR monitor controller is developed. Firstly, in order to amplify the weak AC voltage signal, the high voltage and high precision operational amplifier and active filter are used. High precision Analog-to-Digital Convertor (ADC) and high speed processor are used to process the signal. The measuring circuit can withstand a 600V common mode voltage and simultaneously measure 16 fuel cell single units. It can meet the acquirements of 60kW PEMFC system. In HFR calculation, both the Fast Fourier Transformation (FFT) and amplitude ratio measurement chip are used to check the results. Finally, the controller is tested in the test bench and the actual fuel cell system. The results show that the design is feasible and water content can be estimated accurately in less than 5 seconds.