High-order Sliding Mode Control Research For ICPT System

Wireless power transfer technology has advantages of safety,durability,no inerface friction,takeing power flexible,power supply and power terminal completely isolated etc,which can effectively overcome the disadvantages of traditional power supply.Inductive coupled power transfer,also known as non-contact power transfer,which is regarded as the best solution for short-range wireless power transfer,so that it is widely concerned by scientists all over the world.ICPT system has characteristics with multi-parameters coupling,high order,non-linear,etc,which may make the system difficult to control.Uncertainty of the system parameters and external disturbances can cause instability of the output of the system,so it is necessary to design a controller.This paper introduces the current situation of ICPT technology all over the world,and compares the existing ICPT system control algorithms.It is found that the existing algorithms for voltage regulation have the defects of needing accurate system model,weak robustness to parameter uncertainty and external disturbance,low control precision,low efficiency,applicability is not strong,etc.For these reasons,a high-order sliding mode controller which can track the reference voltage without overshoot,and has strong robustness to parameters uncertainty and load disturbance is proposed for SS type ICPT system.The research and design of this paper are as follows:(1)The circuit model of SS type ICPT system and its basic working principle are analyzed,the equivalent model of the system model is obtained by fourier series expansion method.And the equivalent DC model of the system is obtained.(2)According to the equivalent circuit model,the dynamic equation is established.By analyzing the state-plane trajectories of the output voltage errors in the energy injection mode and the self-resonant mode,the approximate optimal state-plane trajectory curve of the output voltage error is obtained.The system can reach the reference value at the fastest speed and without overshoot,which can improve the dynamic performance and robustness of the system effectively.(3)According to the state-plane trajectory curve of the energy injection mode and the self-resonant mode,the optimal switching point is determined.And the hysteresis parameter is introduced to limit the switching frequency of the sliding mode control signal.Finally,a suboptimal second order sliding mode control algorithm based on state machine is designed and the stability of the controller is proved.On the basis of this,an improved sub-optimal second order sliding mode controller is proposed by optimizing and updating the switching coefficient to eliminate the possible steady-state error of the system.The algorithm can achieve the goal that the output voltage tracks the reference voltage very fast without overshoot;In the load disturbance,the sliding mode control signal can be adjusted to the reference voltage only after one switching.When the system parameters are perturbed,the controller shows a strong robustness.In summary,this paper builds up the Matlab/Simulink model and a 100 W ICPT system experimental prototype to verify the design of the control algorithm.The experimental results are consistent with the theoretical analysis,and the correctness of this controller is fully explained.