Research On Bi-directional DC/DC Converter And Its Control Strategy In Energy Storage System

With the increasing depletion of fossil fuels, renewable energy such as solar andwind, which is pollution-free and renewable, has attracted more and more attention ofresearchers, and gains a lot of research. The micro-grid system based on renewableenergy obtains a very fast development. However, due to the instability and theintermittence of wind, solar and other renewable energy, the micro-grid system becomesless economic and less practical. In order to overcome the shortcomings of renewableenergy, the currently accepted method is to add an energy storage system, which ensuresa smooth transition of the system under different operating conditions of energy, andmaintains the system steady job.Through summing the current development of bi-directional DC/DC converter, theparallel interleaved Buck-Boost topology with coupled inductor is selected as thesystem main circuit structure. After a detailed analysis of the work of the main circuit,the flow characteristics between parallel branches, zero current soft switchingcharacteristics of main circuit and the influence of coupling coefficient onthe main circuit performance are studied. The main advantages of this circuit are that itis able to achieve zero current soft switch and solve the power loss in reverse recoveryof diode. The current sharing characteristic of interleaved branches is very good, and thecurrent ripple is small with compact circuit structure. The small-signal model of themain circuit is built and double-loop controller is designed. The system is steable and itresponses fast.For the three-terminal DC bus power system including renewable energy, batteryenergy storage system and load, a complete storage system energy management strategyis built. And the control strategy is proved valid through MATLAB simulation.Finally, the hardware experimental platform is designed and built, using DSP chipTMS320F28027of Texas Instruments as a system controller. The open loop and closedloop experiments verify the design parameters of the main circuit to be correct and fit,and the energy management strategy of the energy storage system to be effective andfast response.