| With the rapid development of industry,oil,coal and natural gas will eventually be consumed completely.As ideal clean energy in the future,solar energy resources which are rich in resources,wide distribution and great potential for development,have gradually come in people's life.And it will create a new world energy structure.Solar photovoltaic power generation is an inevitable choice to solve the energy shortage in twenty-first Century.In this paper,the research object is H-bridge nonisolated bidirectional DC/DC converter.In order to improve the dynamic characteristics of voltage and current and to improve the voltage stability during switching of charging/discharging mode,the influence of modulation mode and control strategy on four mode switching is studied.A dual carrier modulation mode is proposed to simplify the control mode and improve the dynamic performance.Based on dual carrier modulation method,the fractional order PI controller is adopted to further improve the dynamic performance of the system the dynamic performance of the system.Finally,GUI virtual experiment platform and the hardware experiment platform of 1kW bidirectional DC/DC converter are set up.The main study of this paper is as followed:(1)Unified mode control based on dual carrier modulation.In this paper,a dual carrier modulation strategy is proposed for the H-bridge nonisolated bidirectional DC/DC converter with large overshoot and long regulation time during mode switching.Firstly,the operating principle of converter is analyzed,and then the small signal equivalent model is established.And a dual carrier modulation strategy is used to model the H-bridge nonisolated bidirectional DC/DC converter to transform four switching mode into unified control,simplifies the control algorithm.Finally,the stability of converter is analyzed and verified by simulation.The results show that the proposed method reduces the overshoot and regulation time during mode switching.(2)Analysis and design of fractional order PI~?D~? controller.In order to further reduce the H-bridge nonisolated bidirectional DC/DC converter of the overshoot,settling time and start voltage overshoot,the fractional order PI~?D~? controller is adopted in the outer loop of the voltage.Firstly,the definition of fractional calculus and the combination of Laplace transform are analyzed,and then the approximation and discretization method of fractional order operator are analyzed.By using the Tustin transform method and the fast convergence of CFE algorithm,the fractionalorder controller is discretized,and the discrete mathematical model and its recursive control operator are obtained,which are applied to outer voltage loop controller of bidirectional DC/DC converter.Finally,a simulation analysis based on Simulink is carried out,which achieves the goal of faster response and less voltage overshoot in startup and mode switching.(3)Development of small power experimental platform and analysis of experimental results.Firstly,the small power experiment platform of GUI and the virtual experiment platform of 1kW are developed in this paper.The hardware circuit and software program of the small power experiment platform are designed.The hardware circuit includes: power main circuit,control circuit,drive circuit,signal detection and conditioning circuit.Software programs include: main program flow,ADC interrupt subroutine flow and fractional order control algorithm,flow programming.Finally,the effectiveness of dual carrier modulation and fractional order PI~?D~? controller is verified based on the experiment platform,and simulation results are basically consistent. |
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