Study On Control Strategy Of Permanent Magnet Synchronous Motor Driving System For Industrial And Mining Electric Locomotive

For traditional industrial and mining electric locomotives,DC series motor is often used as traction motor,and it usually adopts series resistance speed regulation or chopper speed regulation.In recent years,three-phase asynchronous motors are used as traction motors of industrial and mining electric locomotives in mines,but the low power density of asynchronous motors has caused difficulties in spatial design of industrial and mining electric locomotives,increased difficulties in maintenance.In addition,their power factor is low.Due to the characteristics of PMSM,such as simple structure,high efficiency,high power density,good safety performance and reliable system,etc.,it is very suitable for the requirements of mine enterprises for safety,efficiency,environmental protection and energy conservation.The driving system based on PMSM will surely have a broad application prospect in the mining traction industry.According to the characteristics of industrial and mining electric locomotives,harsh environment,including heavy load and frequently load variation,etc,this paper specifically studied the drive system with permanent magnet synchronous motor as the core.Centering on the key problems existing in the operation process of industrial and mining electric locomotives,the research work mainly includes the following aspects:?1?In the operation process of the permanent magnet synchronous motor drive system of industrial and mining electric locomotives,the fluctuation of load will cause the speed oscillation of industrial and mining electric locomotives,thus greatly increasing the damage probability of mechanical structures such as reduction boxes of electric locomotives.In this paper,the control method combining sliding mode variable structure control with disturbance observer is studied,and the sliding mode controller based on exponential approach law is used to further improve the static and dynamic tracking performance of motor drive system,and then the feedback controller based on disturbance observer is adopted to compensate the load disturbance.In view of the problem of the chattering of sliding mode control and too long adjustment time,the control method combining complementary sliding mode variable structure control with disturbance observer is adopted,and the complementary sliding mode variable structure controller combining Sg and Sc is used to realize the motor system's static and dynamic tracking performance,inhibit shaking,weaken the overshoot,etc.Then the feedback controller based on disturbance observer is used to compensate for the interference caused by the system's velocity measurement,current measurement as well as the change of load,thus improving the fast response and robustness of the system.?2?Due to the bad conditions in the operation site environment of industrial and mining electric locomotive,such as fog,dust and vibration,the velocity sensor is easy to damage.In addition,the load of permanent magnet synchronous motor varies frequently,bus voltage fluctuates greatly,and the position of common rotor position observation method is inaccurate.In this paper,the initial position of permanent magnet synchronous motor is obtained by high frequency injection method,then the estimated speed is obtained by disturbance observer,and the rotor position of permanent magnet synchronous motor is obtained by integrating the speed.Therefore,this paper designs a new linear matrix inequality?LMI?disturbance observer structure,and then proposes a control method combining LMI disturbance observer with backstepping control,namely,the permanent magnet synchronous motor stator q axis current i_q*are the state variables introduced into the backstepping control structure to disturb the observer reconstruction.The linear matrix inequality?LMI?is used to calculate the observer's gain and then estimate the electric current and i_q,rotational speed,measurement interference d₁ and d₂ of the permanent magnet synchronous motor.After obtaining the estimates of the disturbance observer,the current controller and speed controller are designed,respectively by complying with the backstepping control strategy.?3?Aiming at the problem of generating abundant and considerable regenerative braking energy in the braking process of industrial and mining electric locomotives,this paper makes a mathematical analysis on the braking of industrial and mining electric locomotives and constructs the mathematical model of energy feedback system of electric locomotives.Then according to the mathematical model,the instantaneous absorption reference power of the energy storage system and the energy feedback system is obtained.Through the tracking control of instantaneous power,the absorption power ratio of braking energy of electric locomotive between the energy storage unit and energy feedback unit is adjusted.Later,the optimal energy distribution scheme based on the combination of energy storage and energy feedback system is proposed for regenerative braking energy.A lot of tests and field engineering applications indicate that the proposed complementary sliding mode control based on disturbance observer has a good inhibition effect on the speed oscillation of industrial and mining electric locomotives caused by load fluctuation.The system structure of industrial and mining electric locomotive is more reasonable and more reliable,and the mechanical impact is effectively reduced,thus greatly reducing the mechanical wear,improving the safety of industrial and mining electric locomotive,and greatly reducing the maintenance workload.The estimation of backstepping control based on disturbance observer has a good goodness of fit with the actual speed,which effectively solves the problem caused by the use of speed sensor in permanent magnet synchronous motor drive system for industrial and mining electric locomotives.Abundant and considerable regenerative regenerative energy is produced in the braking process of industrial and mining electric locomotive,and the bus voltage fluctuation and regenerative braking energy recovery are within the normal range after adopting the optimized distribution scheme of improved control strategy.Therefore,it effectively overcomes the defects of low energy density of energy storage device and weak impact power energy of energy feed system,so the power consumption of industrial and mining electric locomotives is significantly reduced.