| Hydrogen energy and fuel cells are an important direction for future sustainable energy development,and fuel cell test systems,as essential equipment in the process of fuel cell common technology research and performance evaluation,play a huge role in promoting fuel cell development.While high-power proton exchange membrane fuel cell technology has matured rapidly in recent years,the corresponding test system suffers from low test power,low precision control of temperature and humidity variables,slow dynamic response and high overall power consumption,which seriously restrict the further commercialization of fuel cell products.This thesis will focus on the fuel cell test system,using the technical route of"module function definition-coupling mechanism analysis-control strategy development-bench application verification",combining finite time thermodynamic analysis and chemical reaction process control theory,through the system multi-module multi-parameter coupling mechanism analysis,intelligent control strategy.The thesis aims to achieve high-precision and low-energy operation of the high-power fuel cell test system by combining finite-time thermodynamic analysis and chemical reaction process control theory,and to provide strong support for fuel cell product development.The main research contents and contributions of this thesis are as follows:1.A lumped-parameter dynamic model of the test system is built to support the development of the system’s control strategy and optimization analysis.Firstly,based on the operation mechanism of fuel cell and related modules,and considering the multi-parameter strong coupling characteristics of the internal modules of the test system,the models of modules such as gas supply and exhaust gas treatment module,humidification module and thermal management module are completed.Then,by correlating the input and output relationship between modules,the physical variable connection and directionality of the module ports are solved,and the coupling model of the test system is integrated.Finally,a 100 k W fuel cell test system experimental bench is built to complete the model validation.The simulation and experimental comparison results show that the maximum error of the test system stack and temperature and humidity performance are within 4%,and the system model conforms to physical reality and can better reflect the performance characteristics of the test system.2.In order to solve the problems of large time lag,large inertia and non-linearity of temperature control,an adaptive thermal management control strategy based on water-cooled heat exchange is designed to solve the problem of high-precision dual-temperature control of fuel cells under different dynamically changing operating conditions.Firstly,on the basis of the thermal management module model of the test system,a fuzzy PID control algorithm is designed to achieve online self-tuning of control parameters and improve the accuracy and stability of temperature control.Then a feed-forward compensation algorithm based on the calculated flow error of the stack exothermic model is introduced to improve the temperature dynamic response characteristics.Finally,the temperature performance characteristics of the system under different test condition change scenarios are analyzed.The results show that the thermal management control strategy has good self-adaptability and robustness,and the control effect is better than the traditional PID control algorithm,the temperature control accuracy is improved to±0.5℃,and the dynamic adjustment time is shortened to 30 s,meeting the requirements of stable,fast and high precision temperature control.3.In order to realize the fast response of the humidity of the test system,a mixed wet and dry gas humidification method is used and feedback linearization theory is applied to achieve good fast response control of humidity and interference suppression in the non-linear humidification module.Firstly,the dynamic control equation of the humidification module is constructed by introducing the kinetic equation of the module actuator.Then the conversion of the non-linear humidification module to a fully controllable linear system is realized through differential homogeneous mapping,and the decoupling between multiple input-multiple output parameters is completed.Finally,on each channel of the decoupled system,a new input vector is introduced into each channel of the decoupled system to design a feed-forward+feedback 2-degree of freedom controller to achieve good trajectory tracking and disturbance suppression of humidity.Simulation and experimental results show that under different operating conditions,the humidification module of the test system can achieve fast humidity response control over the full range,the humidity output has high accuracy tracking of humidity demand without large oscillations,achieving±5%RH accuracy control of the inlet humidity and fast response at 10 seconds level.4.In response to the current problems of high energy consumption and low efficiency of test systems,the research on performance optimization evaluation and comprehensive energy utilization of high-power test systems is completed based on finite-time thermodynamics theory.On the basis of the lumped-parameter model of the test system,the energy use efficiency evaluation function is introduced according to the energy and exergy efficiency,exergy loss,ecological performance coefficient and ecological distribution parameters to study the performance bounds of fuel cell test systems.The distribution of the energy efficiency characteristics of the system under different operating loads is analyzed to identify avoidable and unavoidable performance losses of the system,optimize component matching and screen the system operating conditions,and investigate the influence of different control strategies of temperature and humidity on the system efficiency and power consumption.The study shows that the exergy losses is mainly concentrated in the fuel cell stack,humidifier,exhaust gas discharge and water-cooled heat exchanger,and the improvement of the fuel cell stack performance is the key to optimizing the test system.Under the operating conditions of1A/cm~2current density,the temperature and humidity control strategy of this study can significantly reduce the performance fluctuation,and the comprehensive energy utilization of test system can reduce the exergy losses by 32.1%and improve the efficiency by 34.9%compared with the conventional system. |
PDF Full Text Request