| Switching power supply has been widely used in aerospace,electronic communication and household appliances for its high frequency,high efficiency and high stability.As an important branch of switching power supply,DC-DC power converter has the advantages of small size and high density.However,its topology has strong nonlinearity,and the traditional control algorithm cannot meet people's requirements for power quality because of its short response speed and poor dynamic performance.Because the converter is a typical variable structure system,the control structure is complex,and the good control effect of the sliding mode variable structure control has attracted researchers' attention.Based on the traditional sliding mode theory and the second-order sliding mode theory,this article takes Boost type DC-DC converter as the controlled object to conduct in-depth research.Specific elements include:(1)Starting from different angles,the Boost power converter is analyzed and modeled.Analyze the working principle of the power converter,and explore the principle of boosting in continuous mode,critical mode and discontinuous mode according to the working state of the transducing inductor.The mathematical model of the converter is established by using the small signal modeling method and the state space averaging method.According to the characteristics of the two modeling methods,sliding mode control theory,the structure and characteristics of the converter are deeply understood.(2)In order to study the algorithm at the practical level,the platform construction of Boost power converter is proposed.The TMS320F28335 model DSP produced by TI is used as the core control chip for design.The peripheral is combined with voltage detection,current detection,undervoltage protection,overcurrent protection,MOS protection and drive circuit modules to complete the hardware construction.Based on the CCS7.4 software development platform,the programming design of the software is realized through the combination of C language and assembly language.Through open-loop and closed-loop(PID controller)experiments,the reliability and stability of the hardware and software platform design scheme are verified.(3)Based on the theory of sliding mode control,a first-order sliding mode controller is proposed,which can not meet the requirement of high precision of variable structure system and is sensitive to the change of external environment.The form of exponential power is used in the controller to speed up the system's finite time convergence,and the integral form improves the control accuracy of the system.A simulation model is built in Matlab / Simulink,and experiments are conducted based on the Boost power converter platform.By comparing with PID simulation and experiment,it is proved that the algorithm has better dynamic performance,steady state performance and reliability than the traditional linear control algorithm.(4)Aiming at the problem of "chattering" existing in the traditional first-order sliding mode control algorithm,a new type of second-order sliding mode controller is proposed based on the high-order sliding mode control theory.The design of the algorithm takes into account not only the position error in the state space,but also the motion information of the error state.The state error can make the system converge in a finite time.The coefficient factor of the control method is related to the state variable,and the output can be tracked well.simulations and experiments of the above three algorithms demonstrate that the proposed algorithm improves the dynamic performance,steady-state performance and reliability of boost power converters. |
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