Study On Sliding Mode Control And Its Application Of AC Drive System

The AC drive system is the core of industrial production equipment,which has the performance directly affecting the quality of the modern industrial product.Currently,an AC drive system usually has the characteristic of high voltage,high performance,high efficiency,and green energy saving,which demands higher requirements on control technology.The thesis mainly focuses on industrial production lines that require high-speed control accuracy and dynamic torque response,such as rolling line.In this kind of industrial application,there are many non-linear interference problems in the production process.Firstly,the AC asynchronous motor is the typical non-linear,multi-variable,strongly coupled high-order control object.Secondly,in the actual operation process,the operating conditions of the motor are complex and changeable,and the operating efficiency and the power factor are low,which may lead to lots of control problems.Moreover,the problems caused by the parametric variations and the load disturbance in the AC drive system have not got a good solution.For these reasons,the sliding mode variable structure control is adopted in this thesis to solve the problem of global nonlinearity.However,the chattering phenomenon existing in sliding mode variable structure control itself limits its further engineering applications.The increase in chattering amplitude affects system control performance and anti-jamming capability.Therefore,to weaken the amplitude value of the chattering,the repetitive control is combined with the sliding mode variable structure control in this thesis,and the entire system can meet the requirements of global robust performance.In this thesis,the study object is the induction motor driven by the dual-PWM converter,and the main idea is to exploit the high-performance control strategy to improve the control performance and robustness of the AC.drive system.Ultimately,the aim of the control is to achieve multi-target optimization control in the grid side of the AC drive system as well as the machine side.The main problems are focused on the suppression of the chattering phenomenon,the application of the composite control in the process of braking energy by the PWM rectifier,and the control scheme on the induction motor speed control system.Firstly,the chatting phenomenon limits the further application of sliding mode control,and then the main advantage of repetitive control is to maintain the essential characteristics of the system.It can capture the main laws of the controlled object,and play a leading role in resistance to the external interference.This advantage is very helpful to improve the performance of the sliding mode control.Then,a new composite control strategy is proposed to optimize the sliding mode variable structure control in this thesis.The stability and convergence properties of the proposed control strategy are analyzed by using the Lyapunov theorem.The optimization process of sliding mode variable structure control is repeated by phase plane analysis.Secondly,since the DC bus is an important component in dual-PWM converter system,it is necessary to design a control scheme improving the DC bus voltage regulation.Based on this,sliding mode control is designed and applied in this thesis to suppress the bus voltage fluctuation.Simulation and experimental results show the effectiveness and validity of the new control scheme.Thirdly,the energy generated by the motor brake has the characteristics of high transient and large amplitude.The improper adjustment will result in the sudden increase in bus voltage,which damages the whole system.In this thesis,the composite control strategy realizes the high-quality transient connection of the motor feedback energy.Experiment results show that the proposed control scheme effectively suppressing the pump-induced voltage generated by the DC-side regulation.Moreover,in order to improve the dynamic performance and robustness of the load-side system,the new composite control scheme is applied in the induction motor vector control system.Comparing with the classical sliding mode control,the composite control has improved the robustness of the system testing by the simulation and experimental results.In addition,the speed sensorless control is conducted by applying the sliding mode control.Finally,it is a serious problem for all researchers to verify the effectiveness and the feasibility of advanced control algorithm in the shortest possible time.In this thesis,a set of the real-time simulation program is analyzed and designed,using delay compensation and event capture module.The proposed control scheme mentioned above is quickly verified by utilizing the real-time simulation platform.