The Application Research On New Stability Criterion For Vector Control Motor Speed Regulation System Of Electrical Vehicles

Since the oil reserve on earth will be used up soon, electrical vehicles will gradually replace internal-combustion-engine driven vehicles. Electrical vehicles have been the research hotspot globally. Many types of motors can be employed as driving motors, such as shunt-wound DC motor, series-wound DC motor, brushless DC motor and variable-frequency vector control AC motor. Compared with DC motor, AC motor has simple structure and low production and maintenance cost. And it can be used in rigorous environment. So AC motors are the good choice for electrical vehicles. However, AC motor is a nonlinear and time-variant system. It has the characteristics such as multiple variables, nonlinear and strong-coupling. Although vector control can solve the problem of coupling to some degree, the system is still nonlinear. What's more, during the real running course, there are many disturbance factors. So it is necessary to study the system stability of AC motor speed regulation.For a control system, the first and most important question about its various properties is whether it is stable, because an unstable control system is typically useless and potentially dangerous. For nonlinear control systems, usually the Lyapunov's direct method is employed to analyze their stability property. For many nonlinear systems, unfortunately, the Lyapunov functions are very difficult to construct. And up till now, there is not a general way to construct Lyapunov functions. This is the main drawback of Lyapunov stability theory. The reason is that Lyapunov's direct method requires a monotonic decline energy-like function to be the Lyapunov function, and the condition for system stability is a sufficient condition. For many intelligent control systems, such as fuzzy control systems and ANN control systems, it is very hard (often impossible) to find such an energy-like function.Reference papers [1] and [2] put forward a new stability criterion based on computer simulation for nonlinear time-invariant systems. It expanded the sufficient conditions of Lyapunov's direct method into necessary and sufficient conditions for local stability. It supplies a standard and simple way to select the Lyapunov's function. The relevant proof was given to justify this stability criterion. This thesis analyzes the stability of an AC motor vector control variable frequency speed control system by employing this new stability criterion on the platform of MATLAB/Simulink. And briefly introduces the application and research of the motor regulation control system in EV.