| Bidirectional DC/DC converter has been applied in the fields of the electricvehicles, electric power quality regulation systems and renewable energy generationsystems, etc. In this dissertation, a device of full-bridge current-doubler bidirectionalDC/DC converter is researched deeply, which is based on the background of energystorage systems in microgrid.Firstly, this dissertation discusses the background and significance ofbidirectional DC/DC converters. For photovoltaic storage systems in microgrid,full-bridge current-doubler rectifier is chosen as main circuit of the bidirectionalDC/DC converter, after comparing several typical topologies. The low-voltage side isconnected to the energy storage battery as current-doubler rectifier. The two filterinductors are interleaved and effectively reduce the battery current ripple. Thehigh-voltage side is connected to the main DC bus as a full-bridge. Due to thestartup problems of current source converters, a soft-start circuit is designed byincreasing flyback windings on both inductors. Then, the converter’s workingprinciple and electrical characteristics are analysed under various modes, and thesimulation results are shown.Secondly, the mathematical models is established. Based on the small signalmodels, selection of the loop controller is discussed in detail and a two loop feedbacksystem is chosen, which uses current feedback as inner loop and voltage feedbackas outer loop. The small signal models of bidirectional DC/DC converter presentsobvious differences between the two working states of buck and boost, according towhich,the corresponding loop control blocks are determined and the loop controllerparameters are carefully designed.Micro-grid energy storage bidirectional DC/DC converter has several operatingmodes. An appropriate switching logic strategy, which is called the multi-modelcontrol technology, is chosen after analyzing the switching conditions betweendifferent operating modes. High frequency of switching between operating modes,the complex switching drive logic and control algorithm, make the digital controlsystem the best choice. In this dissertation, a DSP TMS320F28069is used as the main controller to build the digital control system. In addition, the power circuit isdesigned in detail, including power transformer and inductors, selection of filtercapacitors and power switches.Finally, simulations are presented using the C block of PSIM to realize thedigital control system, and a prototype of the full-bridge current-doubler bidirectionalDC/DC converter is developed and fully studied. The simulation results andexperimental results consistently indicate that the full-bridge current-doublerbidirectional DC/DC converter has good steady and dynamic performance. |
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