Research On Speed Sensorless Indirect Stator Quantities Control Of Traction Motor

The construction of China's rail transit is entering the peak period of rapid development, the market of rail transit vehicle has broad prospects. As the key of mass transit vehicles, traction system determines the vehicle's performance directly, which relates to the safety of vehicles, operation quality and energy consumption. In our own independent intellectual property of the rail transit vehicle AC drive system, there are some defects in the traditional direct torque control system, such as large torque ripple,high current harmonics。Particularly in metro traction system of DC power supply, it's easy to cause a large DC current and voltage oscillations problems. The control strategies of motor need to be further optimized and improved. In addition, because the speed sensors are very inconvenient to install and maintain, and their working environment is bad, which are the major source of vehicle failure. Therefore, the study of speed sensorless of electric traction control system is of great theoretical and practical significance. The key technology of rail transit traction power AC drive is studied deeply from these two aspects in this paper.Firstly, the development of AC motor control strategy is reviewed, the development Status of sensorless control technology is summarized and analyzed, and overview of rail electric traction drive system is introduced. T-andΓ-type equivalent circuit of asynchronous motor, mathematical model of inverter, the concept of voltage space vector, and the theory of voltage space vector modulation (SVPWM) are clarified based on mathematical model of asynchronous motor.According to the defects of the traditional method of direct torque control in rail transit vehicle AC drive system, indirect stator quantities control of full range of speed traction motor is studied. A full order flux observer is proposed, which can observe stator and rotor flux of asynchronous motor accurately. Two methods of Flux-weakening control are presented, and a method of over-modulation which can be easy to implement is provided. Also, a time-based deadtime compensation method is proposed. Indirect stator quantities control has been expand to full speed range successfully, which have been verified by simulation and experiment. Simulation results show that the whole speed range of indirect stator quantities control can obtain high dynamic response and suppress the effects of harmonics, it can also solve oscillation of main circuit of mass transit metro rail traction system, which lay a good foundation for the method to apply for the traction of mass transit metro rail system.An in-depth study is carried out for the method of model reference adaptive speed estimation based on Observer, which is widely used in speed sensorless. Starting from traditional method of select the observer gain by using pole placement, a method of model based on the stator flux speed of U-N adaptive identification is proposed for engineering application, and similarities and differences from traditional observer-based speed estimation method are analyzed. According to the characteristic of identification of low speed range is not accurate for the majority speed estimation method at present, the causes of its instability are analyzed, and a new method of speed sensorless is proposed, Which adopts robust control theory to obtain observer gain matrix by solving two bilinear matrix inequalities (BMIs) with MATLAB's LMI toolbox, and Lyapunov stability theory is combined to derive the speed adaptive law. The speed estimation method is applied to direct torque control system and the indirect stator quantities control system of traction motor, MATLAB simulation and experiment are carried out, which show that there are some advantages of this approach, such as system with good stability in the whole range of different conditions, speed can be identified accurately, and the problem of instability in variety of speed estimation method in the low power generation are solved. Finally, the new observer-based speed sensorless method is expended. A observer-based stator resistance identification method is proposed to achieve the speed and stator resistance identification at the same time.Hardware-in-loop (HIL) simulation platform of AC drive of urban rail metro is developed. The composition of the HIL simulation platform, software and hardware platforms, and the method of establishing the real time simulation model of the controlled object are introduced. The simulation platform is verified and improved by some metro application projects. DSP software of speed sensorless indirect stator quantities control system is established and debugged completely based on this platform.