High Performance Direct Thrust Force Control Of Linear Vernier Permanent-Magnet Motor

With the rapid development of urbanization,the urban population and the density of urban building have increased dramatically.More and more serious traffic jam problem is facing greater challenges,strongly limiting the development of efficient and convenient urban.Rail transit,as a new transport,has attracted great attention,in which traction technology has played a quite important role.Compared with the rail transit traction system with the rotary motor,the traction system with the linear motor has significant advantages of simple structure,high efficiency,strong climbing capacity,and small noise etc.In this paper,a novel linear vernier permanent magnet(LVPM)motor is studied,which PMs and armature windings are located in the short primary mover(train),while the long stator is composed of an iron core only(track).And,direct thrust force control(DTFC)is researched.Due to the nonlinear saturation of the speed loop and high thrust force ripple in linear vernier permanent-magnet motor drive,an improved DTFC strategy is proposed.Due to inverter switch open circuit fault,a new open-end winding fault-tolerant DTFC strategy is proposed.The simulation and experimental results verify the correctness of the proposed algorithm.The main research contents of this paper are as follows:1.The structural characteristic of the LVPM motor and the static characteristics of the magnetic field distribution,back EMF,inductance,and cogging force are analyzed,and the coordinate transformation matrices of LPMV motor in different coordinate systems are derived.The mathematical model of three-phase LPMV motor is established,which lays the foundation for the following simulation research.2.The basic theory of the DTFC strategy for LVPM motor is introduced,including topology of the inverter,the basic principle of DTFC system,control of force and flux,and design of observer.The conventional DTFC is implemented based on the basic theory of DTFC,the conventional DTFC is analyzed by building simulation mode,providing a good theoretical basis for below improved DTFC algorithm.3.Due to the nonlinear saturation and high thrust force ripple in conventional DTFC strategy,an improved DTFC strategy based on anti-windup PI controller and duty ratio modulation is proposed.The variable-structure is adopted in the novel anti-windup PI controller,which can make the system quickly exit saturation zone.Duty ratio modulation with a constant switching frequency is adopted in the improved DTFC strategy.The correctness of the proposed improved DTFC strategy is analyzed by establishing model in Matlab/Simulink.The hardware and software of control system are designed,and the experimental platform is built.Contrastive experimental research about conventional DTFC and improved DTFC is carried out on this control experimental platform,verifying the effectiveness of the proposed improved DTFC algorithm.4.Due to inverter switch open circuit fault,a new open end-winding fault-tolerant DTFC strategy is proposed,in which the neutral point of the LVPM motor is opened to constitute open-end winding system,the fault tolerant topology is restructured,an improved dual inverter space vector pulse width modulation is reconfigured by the rest of switches,The simulation analysis and experimental results show that the feasibility of the proposed fault-tolerant DTFC algorithm.