Research On Control Strategy Of Bidirectional DC/DC Converter Based On Sliding Mode Variable Structure

With the rapid development of the economy,the demand for non-renewable energy is increasing day by day,resulting in global environmental pollution and energy depletion,all of which make energy issues an important issue currently facing,and the development of renewable energy is urgently needed.As an important interface of energy storage equipment,bidirectional DC/DC converter plays an important role in the field of microgrid,railway traction power supply system and energy router.Firstly,by analyzing the topological structure of each circuit,the bidirectional halfbridge circuit is selected as the main circuit of this research.According to the working characteristics of this type of circuit,the mathematical modeling and analysis of the converter is carried out by using the state space averaging method,which lays a theoretical foundation for the follow-up control strategy research.Secondly,the basic principle of sliding mode variable structure control strategy is studied,and the feasibility of applying this control strategy in bidirectional DC/DC converter is analyzed.Based on the integral terminal sliding mode and global integral terminal sliding mode variable structure control strategy,and using the average state space model of the bidirectional DC/DC converter,the sliding mode variable structure control law is derived,and the fixed frequency control of the converter is realized by combining PWM technology.Since the sign function contained in the sliding mode control rate will cause the chattering phenomenon of the system,the hyperbolic tangent function is used to suppress the chattering of the system.After the design of the controller is completed,the stability of the controller is proved by using the Lyapunov function.Thirdly,considering the unmeasurable factors such as input voltage and load mutation in the actual control,it is in the Boost and Buck modes of the bidirectional DC/DC converter.The estimation functions of input voltage and load conductance are designed respectively by adaptive method,and the disturbance estimation value is fed back to the controller for timely correction,thereby further increasing the stability and dynamic response speed of the system.Finally,based on the original basis,the control of the bidirectional DC/DC converter is improved,and a compound nonlinear power control strategy is proposed to realize the output power control of the bidirectional DC/DC converter.According to the obtained simulation experiment waveform,the correctness and effectiveness of the designed power control strategy are verified through the voltage calculation formula in different states.Bidirectional DC/DC converters are easily affected by input voltage and load disturbances in practical applications,and the anti-interference ability of the system can be increased by adopting sliding mode variable structure control.At the same time,the PWM equivalent function control method can be used to fix the switching frequency and limit it to the maximum operating frequency of the switching device.On the basis of the original control,the control strategy is further improved to realize the direct power control of the converter,which makes the designed control method more applicable.