Three-Level Direct Torque Control For Permanent Magnet Synchronous Motor Drive System

As the Permanent Magnet Synchronous Motor(PMSM) more and more widely used in electric vehicles and rail transportation and also other industrial areas, it’s critical to have a better performance for its velocity modulation system; Direct Torque Control(DTC) system has the merits of simple control and fast response, when combined with three-level inverter and SVPWM algorithm can reduce the torque and flux ripple and fix the switching frequency, it’s a great way to solve the problem of traditional DTC. Therefore, the study of PMSM three-level inverter DTC system and the design of the PI regulator control algorithm parameters has important engineering significance. In this paper, in order to realize the PMSM-three-level inverter PI algorithm direct torque control and design the parameters of PI algorithm, the three-level inverter PI algorithm direct torque control is deeplily studied, whitch can provide theoretical and technical support for Permanent Magnet Synchronous Motor control in high power applications. Specific research work is as follows:Firstly, the basic mathematical model of PMSM and three-level inverter is introduced, then analyz the three-level inverter voltage vector space and its impact on the neutral voltage. At last, the 60°oortinate system based SVPWM algorithm with theoretical analysis and simulation is studied in detail, and neutral voltage control is embedded in the modulation algorithm.Secondly, the influence of space voltage vector to electromagnetic torque and stator flux is analyzed, on the basis of traditional direct torque control loo-kup switch table method and the structure characteristics of three-level inverter, proposed the synthesized vector-based look-up switch table of three-level direct torque control algorithm; then combine with three-level inverter SVPWM algorithm, the three-level SVPWM based direct torque control is studied, wherein the electromagnetic torque and flux controller is PI regulator, the effectiveness and feasibility of these algorithms have been verified by the simulation results. Then, the parameters of electromagnetic torque and stator flux PI controllers is designed by research the transfer function block diagram of PMSM three-level inverter control system, wherein the design is the amplitude-frequency characteristics of the minimum peak and the second order the "best" model principle,design the parameters to achive, the design results achieve stable and fast dynamic performance in the control system.Finally, The rapid control prototyping experiment platform based on dSPACE real-time simulator and low-power PMSM is established. Inorder to study the proposed three-level inverter- PMSM Direct Torque Control algorithm, three-level inverter modulation algorithm is compiled and simulation model is conpleted on the platform. The simulation results and experimental results verify the validity and correctness of the direct torque control algorithm.