Research On Nonlinear Control Strategy Of DC-DC Converter

With the development of society,people have higher and higher requirements on the power quality output from power electronic devices.As a switching nonlinear system,the traditional linear control strategy is difficult to meet its high performance requirements,so more and more scholars focus on the nonlinear control of power electronic converter.In order to improve the performance of power electronic converter,the study of its nonlinear control strategy has important theoretical significance and practical value.Sliding mode variable structure control is a nonlinear control method with good control performance.It is widely used in many fields because of its strong robustness and insensitivity to system parameters.At the same time,the feedback linearization nonlinear control method based on the differential control theory has also attracted the attention of many scholars in recent years.Compared with the traditional linear control method,this kind of control method has better dynamic and static performance indexes.In this paper,the Boost type dc-dc converter is selected as the research object.Firstly,the mathematical model is established by using the state space average method.Then,according to the sliding mode variable structure control theory and the PID control idea,the sliding surface is established after selecting the state variable.Aiming at the chattering problem of sliding mode control system,the equivalent control expression is redesigned,and the control parameters are designed according to the relationship between sliding coefficient and system dynamic response.Finally,a new sliding mode control strategy is obtained.Simulation in MATLAB/Simulink verifies the superiority of the control strategy through the simulation of startup response characteristics,input voltage disturbance,load disturbance and system component parameter disturbance.Boost converter with capacitor voltage as the output performance is not the minimum phase characteristics,with zero dynamic instability.To solve this problem,refer to PI voltage and current double loop control idea.Firstly,based on the Boost converter’s affine nonlinear model,the zero dynamic stability of the system is verified when the inductance current is selected as the output.Then a sliding mode variable structure control strategy based on accurate feedback linearization is proposed.The control strategy uses the inductive current controlled by sliding mode as the inner ring and the capacitive voltage controlled by PI as the cascade structure of the outer ring.Simulation results show that the control strategy has good dynamic and static characteristics and strong robustness.