| In recent years,with the increasing problem of energy shortage and environmental pollution,the new energy industry has been growing rapidly,in which photovoltaic power generation is the main force in the development of new energy.However,photovoltaic power generation is vulnerable to environmental impact,and its power generation volatility and indirectness will impact on the power quality and stability of the grid.At this time,the bidirectional DC / DC converter with energy storage device becomes an important part of photovoltaic energy storage system.In this paper,the research status of the topology and control mode of bidirectional DC/DC converter is analyzed.Based on the analysis,the interleaved bi-directional DC/DC converter is selected as the research object,and its working principle is analyzed and the small signal model is established.In order to solve the problems of output current distortion,large current stress,increase of switching loss and decrease of system stability caused by unbalanced current of interleaving topology,firstly,based on the analysis of common current sharing methods,the control strategy of duty ratio distribution method is introduced and improved;the improved duty ratio distribution method collects the total inductance current and the inductance current of each phase respectively By comparing 1/2 of the total inductance current with the inductance current of each phase,the duty cycle of each switch tube is determined through the comparison results,so as to ensure that the two-phase inductance current is equal and achieve the purpose of current sharing.Secondly,based on the established mathematical model of bi-directional DC/DC converter,a double closed-loop controller is designed for the proposed duty cycle allocation strategy.The duty ratio allocation method is added to the current inner loop.The corresponding PI regulator parameters are determined by analyzing the open-loop transfer functions of voltage and current in the rise and fall modes.The baud diagram shows that the PI parameters are reasonable.Thirdly,the hardware circuit parameters and control chip of bidirectional DC/DC converter are selected,the software system is analyzed,and the DSP resource allocation is given.Finally,the simulation model of the converter is built by using PSIM simulation software,and the simulation experiments are carried out to verify the circuit in the up and down mode.According to the selected hardware parameters,an experimental prototype is developed.The experimental results show the correctness and feasibility of the proposed control method.Figure [67] table [2] reference [66]... |
