Research On Direct Torque Control Of PMSM Based On Space Vector Modulation

Permanent Magnet Synchronous Motors(PMSM)is widely used in the high performance electrical control industry due to its high power density,high efficiency and compact size.PMSM is a complex system with nonlinear,strong coupling and multi-parameters.Direct Torque Control(DTC)is widely used in motor control due to its fast dynamic response,robustness and simple structure.The following research work is carried out for Direct Torque Control of permanent magnet synchronous motor:(1)Establishing the mathematical model of PMSM in different coordinate systems,analyze the basic principles of traditional direct torque control,study and analyze the advantages and disadvantages of traditional direct torque control through simulations.(2)Realizing two kinds of Direct Torque Control based on Space Vector Modulation(SVM).SVM uses vector synthesis to generate more voltage vectors.It has the advantages of low switching frequency and torque ripples,which can effectively solve the Problems in the traditional Direct Torque Control of the hysteresis control.such as flux linkage,large torque ripple,and switching frequency variation(3)Aiming at the robustness of the speed controller,a new variable speed reaching law is designed.The new variable speed reaching law combines the inverse hyperbolic cosine function of the system state with the variable exponential approach law to realize the sliding mode based on the new variable speed reaching law.The controller enhances the approach speed of the system and reduces steady-state chattering to improve the system's anti-jamming capability.Finally,it is verified by simulations.(4)A novel stator flux observer based on Third-Order Generalized Integrator phase-locked loop(TOGI-PLL)is designed.Based on the traditional second-order generalized integrator(SOGI),the new stator flux observer uses the third integral term to eliminate the influence of DC offset,which solve the following problems in the traditional voltage model: DC offset,resistance change dependence,initial value problems,and poor performance at low speeds.Finally,the feasibility of TOGI-PLL to observe the flux linkage is proved by simulations.(5)Designing the software and hardware system of PMSM-DTC,and develop the experimental platform based on Cortex-M4.The experimental results show thatthe system with high speed control precision and fast dynamic response.