Time-sharing Supplying Full-bridge Buck Dual-input DC-DC Converter Mode Distributed Generation System

As recyclable and clean energy sources,the new energy sources such as photovoltaic and wind power have been paid more and more attention from governments and researchers all over the world.Research and utilization of new energy has become an important measure to alleviate the shortage of energy supply and environmental degradation.The power supply system with single kind of energy is generally unstable,discontinuous and changed with the environment.In order to improve the stability and flexibility of power system,realize the full use of various new energy sources,researchers have proposed the multi-energy joint-power-supply system.The time-sharing supplying full-bridge Buck dual-input DC-DC converter mode distributed generation system was proposed and analyzed in detail under the research status and development of multi-input DC/DC converter mode distributed power generation system of new energy.The converter is composed of full-bridge Buck mode dual-input DC-DC converter and the power polarity reversal inverter.Multi-energy works at the mode of time-sharing power supply.The converter has the characteristics of simple circuit structure,high-frequency electrical isolation,stronger voltage matching ability,quasi-single-stage power conversion,higher efficiency and much lower switching stress.Maximum power output energy management strategy was adopted in this generation system.Two input voltage loops were built at the former stage to maintain the DC bus voltage stable and achieve the maximum power output of photovoltaic cells and fans.The instantaneous current control strategy was adopted to realize the grid current control at the latter stage.On the basis of energy management strategy,the system was modeled to obtain the transfer function and analyze the stability by Bode diagram.The characteristic of steady state principle and high frequency switching process of generation system were analyzed in detail.Some schemes were proposed to reduce the voltage spike caused by the leakage of primary and secondary side of transformer.Design criteria for key circuit parameters,such as input filter capacitor,high frequency transformer,LCL filter,active clamp capacitor and power switches,were deduced in detail.The converter simulation model was built by PSIM to simulate and analyze the steady state,dynamic state and MPPT state.A prototype of 3kW 240?360VDC/220V50HzAC time-sharing supplying full-bridge Buck dual-input DC-DC converter mode distributed generation system was designed and developed to carry out the experiment of grid connection by using two photovoltaic sources respectively,and the situation of input voltage mutation and load mutation were also tested.In this paper,steady and dynamic performance of the system were analyzed,and important conclusions were obtained.The proposed circuit topology and control strategy of energy management were verified to be correct and feasible.Two input sources output maximum power.The converter has the advantages of good steady and dynamic performance,high output current quality and high conversion efficiency,and has important theoretical value and application prospect in medium and high capacity multi-energy joint-power-supply system.