| Nowadays,the problem of environmental pollution in the world is becoming more and more serious,and energy is in short supply,and the development of new clean energy is highly regarded.Solar energy is attracting worldwide attention and recognition because of its abundant reserves,wide distribution,green environment and other unique advantages.Therefore,how to develop and utilize solar energy efficiently has been the focus of attention all over the world.In photovoltaic power generation system,bidirectional DC-DC converter plays an important role because it can realize energy bidirectional transmission and stabilize bus voltage.The bidirectional DC-DC converter studied in this project applies the interlaced parallel magnetic coupling technology to the Buck-Boost topology,adding the fuzzy control to the double closed loop control,which has obtained the low inductor current ripple,the dynamic performance and the steady state performance,the precise control and the fast response,which provides key technical support for the efficient utilization of photovoltaic power system.Firstly,on the basis of the research status of bidirectional DC-DC converter and the development of photovoltaic power generation industry,according to the demand of photovoltaic power system,the main circuit topology adopts Buck-Boost topology with small voltage stress.The interlaced parallel technique and inductively coupled technique are introduced in this topology,and the performance of the two-phase interleaved magnetically coupled bidirectional Buck-Boost converter in two modes is analyzed.Secondly,the main circuit of the converter with high voltage side 400 V and low voltage side 192 V is designed.The design of inductor parameters,switch device selection and filter capacitance are completed.A double closed-loop control strategy is selected.The state-space average method is used to establish the mathematical model of Buck and Boost,and the corresponding current loop PI controller and voltage loop PI controller are designed.The Bode diagram is simulated by using MATLAB to simulate,verify the accuracy of the PI controller design.Thirdly,the voltage outer loop of the bi-directional DC-DC converter adopts fuzzy PI control,the current inner loop adopts traditional PI control,and the parameters of the PI controller are tuned online,aiming at its nonlinear and time-varying characteristics.The fuzzy PI controller is designed according to the basic principles of fuzzy PI control.The membership function and fuzzy rule base of fuzzy control are determined.A fuzzy rule base is established in the MATLAB fuzzy toolbox to draw the fuzzy inference characteristic surface of the system.Finally,using DSP TMS320F28035 as the main control chip,the main program flow and the fuzzy PI controller algorithm are designed.The simulation models in Buck and Boost mode are established in MATLAB/Simulink to verify the control accuracy and dynamic response speed of the system in the two modes.The experimental results show that the use of fuzzy PI control in the voltage outer loop,the current inner loop using conventional PI control to improve the dynamic response speed,and the system control accuracy is higher. |
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