Research And Realization Of Back-to-back Three-level Pmsm Speed Regulating System

Electricity,is the main way of energy consumption because of its convenient,clean and efficient.At present,under the energy tense situation,the efficient utilization of electric energy has becomemuch more important.Therefore,it has been becoming one of the hot issues of domestic and foreign scholars how to ensure the energy to meet the load needs and realize the efficient power transformation.With the continuous improvement of power conversion technology and device technology,PWM Converter has been widely used in the field of power conversion,such as power transmission and distribution,motor speed regulating system.In this thesis,focusing on the application of four-quadrant speed regulating control for PMSM the three-level power converter control system with back-to-back has been studied.Aiming at the control demands of the system,a lot of works have been done,such as designing the control strategy of the system under different operating conditions,constructing the experimental platform of speed regulating system.And then the correlative theoretic simulation and system experiments are accomplished.In addition,a midpoint balancing control strategy is designed and applied to the system implementation to solve the problem of the midpoint imbalance in three-level SVPWM control.Firstly,based on the analysis of the general topological structure of the back-to-back three-level permanent magnet synchronous motor speed regulating system,the mathematic models of power converter and motor under different working conditions are established separately.Then,according to the theory of voltage oriented control and the principle of PMSM vector control,the system is designed to realize the forward operation control strategy and backward operation control strategy respectively.Based on the research and analysis of the three-level SVPWM control method and the mechanism of the midpoint imbalance in the main circuit,considering the difference of the small vectors effects on the midpoint current,the midpoint balancing control strategy is proposed.Secondly,the system simulation model has been constructed on the MATLAB/Simulink software platform to complete a series of simulation experiments.The simulation results have fully validated the correctness and feasibility of the system control strategy.Thirdly,on the basis of theoretical analysis and simulation verification,the process of hardware circuit design,the selection of main devices and the software flow of control system have been elaborated inthis thesis.Finally,combining the topology of three-levelvariable frequency speed regulation system,the experimental platform of PMSM speed regulating systemhas been built to complete the experiments of the forward andbackwardsystem operationand obtain a lot of experimental results.The results of the experimental data have shown that the control system has got good dynamic and steady performance,Therefore,the validity andrealizability of the control system strategy research,hardware circuit design and control software implementation have been proven successfully.