| Development and use of new energy is an important method to solve the problem of energy depletion and environmental pollution, but the instability in new energy power makes a bad power quality and potential security risk when connected to grid. Micro grid introduced in energy storage technic can buffer the new energy power fluctuation and improve the reliability of the grid connected operation. Development of Vanadium redox flow battery and some other clean energy storage battery promotes the large-scale new energy grid connected technic from theoretical feasibility to realization. Therefore, as a conversion device in energy storage system, research on vanadium redox flow energy storage converter is very important.According to charge-discharge characteristics of the 5kW/20 kWh vanadium redox flow battery and requirements of the Micro grid operation, some developments for the energy conversion device is done in this paper. Firstly, the overall circuit structure is determined, mathematical model of energy storage converter is built, and the counting process of main circuit parameters is designed. Control strategy of battery charging is researched in detail, PI controller is designed, according to the shortage within it, fuzzy control and internal model principle is brought in the controller, the result is verified by simulation at last. In addition, according to the questions of stability and accuracy based on the LCL filter, a split-capacitor passive damping middle current control strategy is proposed in the paper, and the availability of the control strategy is proved by simulation, which based on design and stability criterion.Secondly, software and hardware platform of the system is determined based on the certain scheme. The hardware platform includes control circuit、sampling circuit、driving and interface circuit、protection circuit and control power supply. The software platform includes work procedure of the converter and some interrupt program such as standby interrupt、PWM pulse interrupt and communication interrupt and so on. Some primary function programs is analyzed in detail, including PLL、controller and startstop timing sequence, et al. According to communication and remote control requirements in the micro grid, external communication program is designed.Finally, 5kW vanadium redox flow energy storage converter is built based on the software and hardware platform designed before. By experiment in the field debugging, experimental data is obtained, which including data of DC-DC part、DC-AC part and external communication interface experiment. The experiment data proved that the converter designed by this paper can accomplish basic function such as chargedischarge operation、island operation、interface and remote control function which required by the micro grid. In addition, unity power factor operation and steady sine current waveform is accomplished on the grid side, which means the converter has a good control effect. |
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