Research On Improving Energy Efficiency Of Fuel Cell Truck Power System

A fuel cell vehicle usually refers to an "electric-electric" hybrid vehicle whose power system is composed of a fuel cell and a power battery.The fuel cell is the main power source,and the power battery is used as an auxiliary power source.The energy efficiency of the power system directly affects the energy consumption of the power system,that is,the equivalent hydrogen consumption of the vehicle and the driving distance.Improving the energy utilization rate of the power system is of great significance to the application,promotion,and development of fuel cell vehicles.To improve the energy efficiency of the power system,researches are mainly carried out from two aspects: reducing system energy consumption and increasing system energy.The energy management strategy optimization of the power system can realize the effective energy output control of the fuel cell system and the power battery system.On the premise of meeting the vehicle power demand and ensuring the performance of the power battery,the fuel cell system can run smoothly in the high-efficiency range and reduce the energy consumption of the power system.As one of the important auxiliary systems of fuel cell vehicles,the electric air conditioning system has high energy consumption during the heating process,which seriously affects the energy efficiency of the power system.Therefore,the optimization of vehicle power system energy management strategy and the development of vehicle integrated thermal management system which can effectively utilize the waste heat of power system can be studied to achieve the reduction of power system energy consumption.In the process of fuel cell vehicle driving,brake system and suspension system will lose a lot of energy.Therefore,it is necessary to recover the braking energy and vibration energy in suspension system.The recovered energy is stored in the power battery in the form of electric energy,which can increase the energy of the power system and improve the energy efficiency.At present,the brake energy recovery technology is relatively mature and has been widely used in the field of fuel cell vehicles.This paper mainly studies harvest vibration energy in suspension system.In this paper,takes fuel cell truck as the research object,and takes improving the energy efficiency of vehicle power system as the research objective,and focuses on optimizing vehicle power system energy management strategy,developing vehicle integrated thermal management system based on heat pump air-conditioning,and using piezoelectric material to harvest vibration energy from suspension system,to achieve energy efficiency improvement of the truck.This research mainly includes the following key contents:(1)The topology of the fuel cell truck power systemBased on the vehicle design requirements of the target model,the parameters of the drive motor,fuel cell,and power battery are matched and selected.Then,the fuel cell system performance test is performed.The rationality of the matching results is verified through Cruise software.(2)The energy management strategy optimization of the fuel cell truck power systemA fuel cell truck power system model is established,and a fuzzy control energy management strategy is proposed to realize the effective control of the composite power system.Optimization variables are selected through experimental design and sensitivity analysis.An approximate vehicle simulation model based on an elliptical basis function neural network is established,and a multi-island genetic algorithm is used to optimize the fuzzy control energy management strategy.Simulation is performed under four-cycle conditions to verify the effectiveness of the optimized fuzzy control strategy and the feasibility of the optimization method.The simulation results show that the energy efficiency of the vehicle power system and driving range are improved.(3)Vehicle integrated thermal management systemThrough the performance analysis of the heat pump air conditioning system,an integrated thermal management strategy is proposed.A logical threshold control method is used to select and switch operating mode of the vehicle integrated thermal management system,so as to realize the coordinated management of the heat in fuel cell,power battery,cab and electrical system of the motor.The proposed method can realize the effective use of the waste heat of the power system and reduce the energy consumption of the air condition during the heating process.Thus,the energy efficiency of the power system can be improved.(4)Energy harvesting characteristics of the suspension system with a novel piezoelectric energy harvesting deviceAccording to the power generation characteristics of the piezoelectric material and the vibration energy characteristics of the suspension system,a novel piezoelectric energy harvesting device is designed.The vibration model of the dual-mass piezoelectric energy harvesting suspension system is established by equating the stiffness and damping coefficient.The energy harvesting characteristics of the suspension system are analyzed through experiments and simulation results.At the same time,the credibility of the model is also verified.This solution can effectively solve the problems of a complex structure,large size,and difficult installation of the existing energy harvesting device.(5)Piezoelectric energy harvesting suspension system based on non-contact magnetic forceA novel piezoelectric energy harvesting device with low friction loss and the non-contact magnetic force is proposed.The nonlinear variation law of the energy harvesting device output power is revealed by analyzing the vibration model of the suspension system.The influence of recovered energy on power system energy,power system energy utilization rate,and mileage is further analyzed.Then,a test platform is built to explore the output voltage and recovered power characteristics of the energy harvesting device.The test results verify the credibility of the magnetic excitation model and the feasibility of the modeling method.