| As a representative construction machinery for earthwork excavation,hydraulic excavator has an irreplaceable position in the rapid development of infrastructure.The traditional hydraulic excavator uses the diesel engine as the power source,and the violent fluctuation of the excavation condition makes the engine working point difficult to work in the high efficiency range,resulting in low energy efficiency and poor emission characteristics.Moreover,during the process of lowering the boom demand of the excavator,a large amount of boom potential energy is consumed by the throttle valve,which makes energy wasted and causes system heat,reducing the energy efficiency of the excavator further.With the current trend of energy saving and emission reduction,the number of research related to energy saving of hydraulic excavators has increased gradually.How to improve the energy efficiency and reduce emissions of hydraulic excavators has become one of the hot topics.Although the energy-saving technology of the hybrid excavator can effectively improve the energy efficiency of the hydraulic excavator and reduce its emissions,however the overall efficiency is limited by the maximum efficiency of the engine,and there is still a problem of exhaust gas discharge.Therefore,this article directly substitutes the engine with the efficiently motor to drive the original hydraulic system,which completely eliminates the low energy efficiency and emissions of the engine;replaces the boom hydraulic cylinder with the electric cylinder to drive the boom and recover the potential energy of the boom,to further improve the energy efficiency of the excavator;the energy storage system is designed to assist the power supply to drive the motor and store the feedback energy when the motor brakes,and an energy control strategy is designed to control and allocate the energy transfer.Based on the motor power system model,The energy storage system model and energy control strategy model,the operation characteristics and energy consumption characteristics of the hydraulic excavator power storage system were studied.The details are as follows:1.This paper puts forward the scheme of the hydraulic excavator of this electric drive,and compares the working characteristics and the working principle of key components:the permanent magnet synchronous motor,electric cylinder and super capacitor.Then the mathematical model of AC permanent magnet synchronous motor drive system is established,and the mathematical model of bidirectional DC/DC converter and supercapacitor energy storage system based on equivalent resistance is established.2.Taking the calculated motor efficiency Map as the construction purpose of the motor model,the simulation model of the main motor drive system as the main power source and the power source of the boom electric cylinder are established by using the equivalent mechanical loss method in SimulationX software.The simulation model of bidirectional DC/DC converter based on full ripple modeling method is established later.The parameters and controller of bidirectional DC/DC converter are designed,and the super capacitor group model based on equivalent resistance is established.On this basis,the simulation model of the pure electric drive hydraulic excavator power storage system is constructed.3.Based on the simulation model of the pure electric drive hydraulic excavator power storage system,through the functional analysis of the energy storage system requirements,the requirements of the energy management strategy are put forward.Under the conditions of typical mining cycle and the requirements of energy control strategy,the logic judgment control strategy model and the fuzzy system control strategy model are respectively formulated in SimulationX software.4.With the boom single action simulation condition,the energy-saving effect of the original electric drive system and the electric drive system proposed by the scheme is simulated and analyzed in the SimulationX software in driving the boom.Then,under the whole combined mining operation conditions,the power fluctuation characteristics,efficiency and energy consumption characteristics were compared with simulation results of following systems:the original electric drive system,the electric drive system without the energy storage system proposed by the present scheme,the electric drive system with the energy storage system controlled by the logic judgment strategy and the electric drive system with the energy storage system controlled by the fuzzy control strategy.The research results show that the electric drive system used in this scheme can reduce the coupling energy consumption in driving boom;The boom electric cylinder can recover and utilize the gravitational potential energy when the boom is lowered;the energystorage system can reduce the maximum power supply under the constraint of the energy control strategy.Under the high energy saving rate of the existing electric drive excavator system,the energy efficiency value of about 17.8%can be further improved. |
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