| Under the pressures of traditional energy crisis and environmental protection, thepace of the new energy development is unstoppable. The solar energy gains more andmore popularity with people for its inexhaustible and green, and the photovoltaic systemdevelops rapidly. Bi-directional DC/DC converter is connected to the DC bus and energystorage system, and the Buck-Boost bi-directional DC/DC converter is widely used in thephotovoltaic system.Firstly, the traditional bi-directional Buck-Boost DC/DC topology is improved in thispaper, and the improved topology inherits the advantages of the traditional one. By usingPWM plus phase-shift control strategy, the operation mode switching is achieved bychanging phase shifted angle. Based on the detailed theoretical analysis of Buck and Boostoperation modes, we know that the new topology has many characteristics, for example,the current stresses and voltage stresses on its switches are small, soft switching can beachieved in a wide range. The open-loop simulation results based on PSIM prove thecorrectness of the theoretical analysis.Secondly, the mathematical models and frequency characteristics of the improvedconverter is analyzed. By designing current regulators and voltage regulators for Buck andBoost modes respectively, the system has excellent static and dynamic performances. Thecurrent regulator in inner loop decides the system response to input voltage, and thevoltage regulator in outer loop decides the system response to load current. Theclosed-loop simulation results based on MATLAB verify the feasibility of thecompensating network.Finally, the main circuit, sampling circuit and driving circuit are designed, at thesame time, the components are selected, and the circuit boards are drawed. The controlstrategy of the whole system is designed. The program is written according to theprocedure flow chart. The experimental platform is established based on TMS320F28335DSP digital control. The open-loop and closed-loop experiments under Buck and Boostoperation modes are performed, and the experimental results prove that theoretical analysis is consistent with the experimental results. |
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