| Railway engineering vehicle is an indispensable and important equipment in the construction,operation and maintenance of rail transit lines,which has been widely used.The traditional internal combustion railway engineering vehicle can’t recover regenerative braking energy,and the fuel efficiency of internal combustion is low,the noise is large and the exhaust emission is serious under the operation characteristics of low speed,heavy load and frequent start and stop.Especially in the special environment like subway and tunnels,the exhaust emission and noise have caused great personal injury to the engineering technicians.The transformation and upgrading of the internal combustion railway engineering vehicle is imminent.The battery track engineering vehicle has the characteristics of no emission and low noise,which can effectively solve this problem,but its application is still not optimistic,mainly due to the large current impact of start-up and acceleration,low energy regeneration efficiency and short mileage.With the advantages of high power density and high energy regeneration efficiency,hydraulic hybrid technology has achieved good application in engineering vehicles.Inspired by this,this paper designs a set of electro-hydrostatic hydraulic hybrid powertrain of battery track engineering vehicle,aiming to improve and enhance the dynamic and energy saving characteristics of battery track engineering vehicle by combining the advantages of high energy density of battery,high power density of hydrostatic transmission and high energy regeneration efficiency of accumulator.Firstly,according to the structure of powertrain of the battery rail engineering vehicle,the structural form and configuration scheme of the electro-hydrostatic hydraulic hybrid powertrain are determined,the principle of the electro-hydraulic hydraulic hybrid powertrain is improved,and the system parameters were matched with the technical parameters and the dynamic model of the rail engineering vehicle.Secondly,aiming at the recovery and release of the braking energy,the key factors that affecting the energy recovery of hydraulic regenerative braking are analyzed.Three different energy coupling release modes of accumulator were proposed,and the power and energy saving characteristics of rail engineering vehicle when accelerating under different energy coupling release modes are analyzed.The simulation and test were carried out.The results show that the initial speed of vehicle braking and the strength of hydraulic braking are the key factors that affecting the energy recovery.The flow coupling at the pump inlet and torque coupling have higher energy release ratio and efficiency of the accumulator than the flow coupling at the pump outlet,and the energy saving effect is more obvious.Then,aiming at the problem of large starting current of traction motor of rail engineering vehicle,the starting current control method based on the reverse driving of hydraulic pump / motor is proposed on the basis of the flow coupling at the pump inlet.The short-circuit current vector method and the position sensorless vector control method based on the stator flux integration are used to control the motor starting with initial speed.The simulation models are carried out in MATLAB / Simulink and AMESim.The results show that the proposed method can effectively reduce the starting current,which is greatly affected by the initial speed and starting load of the motor,and the higher the initial speed,the lower the starting current,the larger the load,the greater the starting current.Finally,in order to improve the energy efficiency of the battery rail engineering vehicle,according to the working condition characteristics and the composition of the electro-hydraulic hybrid power system,the principle of power distribution is determined,the working modes of the system are divided and the switching rules of each working mode are determined.The energy management strategy based on the rules is formulated,which is simulated and analyzed in AMESim and MATLAB / Simulink.The results show that the rule control strategy is feasible and effective,which can control the switching of various working modes well,and make the rail car have good speed regulation performance.Under the given slope and the established operating conditions,the electro-hydrostatic hydraulic hybrid powertrain shows better energy saving effect,which can reduce 50.4%,31.04%,9.6% and 4.12% battery energy consumption respectively under the 0 ‰,3 ‰,10 ‰ and20 ‰ slope,and reduces the peak power of the railway engineering vehicle a certain extent. |
