Research On Primary Permanent Magnet Linear Motor And Control Method For Urban Rail Transit

Considering the environmental pollution and the traffic congestion,urban rail transit with the advantages of large transportation volume,fast speed and green environmental protection is increasingly favored by the government and the people.Since the permanent magnet and the armature winding are all mounted on the mover,the primary permanent magnet linear motor naturally attracts the attention of scholars at home and abroad in the long distance transportation system such as urban rail transit.The urban rail transit traction system is a multiple primary permanent magnet linear motor traction system,which will inevitably lead to a large increase in the number of application current sensors,and the failure rate of the current sensor is also increased.In order to ensure the stability and safety of the primary permanent magnet linear motor traction system for urban rail transit,the current sensor fault-tolerant control of the urban rail transit traction system is very important..This topic develops research on the primary permanent magnet linear motor traction system for urban rail transit.The main research contents of the thesis are listed as follows.1)The background and the significance of this thesis are explained.The development status of urban rail transit and the research status of urban rail transit linear motor traction system are introduced.2)Electromagnetic design and modeling were carried out for the primary permanent magnet linear motor.First,the finite element analysis was carried out to calculate the static characteristics of the permanent magnet flux,back electromotive force,detent force and electromagnetic thrust.Secondly,the power equation of the primary permanent magnet linear motor is established and the dimensional equation of the motor is derived.Finally,the mathematical model of the dq coordinate system of the primary permanent magnet linear motor is established,which provides a theoretical basis for the later control strategy and experimental verification.3)A novel direct thrust force control strategy is proposed for a single DC-link current sensor.The first phase current is directly measured by the DC-link current sensor.According to the principle of limited delay measurement,the second phase current is obtained,and then the three-phase current is according to the fact that the summation of three phase currents is zero.In order to avoid the measurement current being sank in a certain phase for a long time,the voltage vector is re-selected according to the single target optimization principle once the sink time reaches the limit time.The novel direct thrust force control maintains the same steady-state and transient performance as standard direct thrust force control.4)A fault-tolerant control strategy is proposed for a single-phase current sensor.First,the dq-axis current is estimated from the dq-axis reference current and the residual phase current,and the correctness of the estimation is theoretically proved.Second,voltage decoupling is used for the first time in single phase current sesnor fault-tolerant control,which greatly increases the current dynamic response.Compared with the existing fault-tolerant control,the proposed fault-tolerant control has better robustness and transient performance.5)A hysteresis current control strategy is proposed for current-sensorless control.In theproposed current-sensorless control,no current sensors are required,and the phase currents are estimated by the PPMLM model.The reference phase currents of the faulty mover drive are determined by other healthy mover drive,which takes full advantages of the multi-motor feature.Ignoring the tracking errors,both the faulty and healthy mover drives can have same estimated synchronous currents.For a motor,the actual and estimated synchronous currents have one-to-one relationship.Due to this relationship,both the faulty and healthy mover drives can have same actual synchronous currents.Because the estimated synchronous currents are just an interface between the faulty and healthy mover drives,the proposed current-sensorless control will not be affected by the variations of motor parameters.6)An experimental platform for primary permanent-magnet linear motor traction system is established based on dSPACE.