Research On Control Methods Of Fractional-slot Concentrated Winding Permanent Magnet Machines

Fractional slot concentrated winding permanent magnet machine has been widely applied in more and more fields because its advantages of high torque density,low cogging torque and low ripple torque.However,the operation of the machine cannot be separated from the control.The output performance of the machine depends on the control method in addition to the body structure.In view of the excellent performance of the fractional slot concentrated winding permanent magnet machine,this thesis takes this kind of machine as the research object,tries to adopt different control methods and improve them to study their control performance.Firstly,the mathematical models of the fractional slot concentrated winding permanent magnet machine in different coordinate systems are studied.The magnetic field characteristics of the machine are analyzed and the variations of the dq-axes inductances are obtained by using the finite element analysis software.The time-varying q-axis inductance is identified by the on-line parameter estimation method to reduce the influence of magnetic saturation and lay the foundation for improving the control performance of the machine.Secondly,the sliding mode control method has strong robustness to the changes of internal parameters and external disturbances,so it is introduced into the fractional slot concentrated winding permanent magnet machine control system with magnetic circuit saturation characteristics.Based on the traditional sliding mode theory,an improved exponential reaching law is proposed to reduce the influence of the chattering problem and improve the low-speed operation state of the machine.The simulation results show that the proposed method is simple and easy to implement,which can effectively improve the output response performance and enhance the robustness of the system.Finally,in order to realize the machine control in the full speed operating range,the maximum torque per ampere control at low speed and the flux-weakening control strategy at high speed are used.The improved sliding mode control method is applied to build the speed controller and the whole machine control system because of its excellent performance.The simulation results show that compared with traditional PI control algorithm,the dynamic and steady-state characteristics of the adopted method in the full speed range are greatly improved.