| Energy storage system is the important part of new energy power generation system,and the advantages of the vanadium redox flow battery makes it the trend of large-scaleenergy storage, the bidirectional converter between the vanadium redox flow batteryenergy storage system and the electricity grid is become one of the most importanttechnologies to achieve the large-scale application of the vanadium redox flow battery.With the advantages of high power density, adjustable input power factor, small currentharmonic components and no need of the bulky DC component, the AC/DC matrixconverter can satisfy the demand of the energy storage system. In this paper, the mainlyresearch is about the control strategies of the AC/DC matrix converter based on the energystorage: charging/discharging control strategy and power factor control strategy.The topology and the working principle of the AC/DC matrix converter is given,current space vector modulation strategy is deduced, and two zero vector modulationalgorithms is chosen. The current four-step commutation method is introduced. Based inMatlab/Simulink, the simulation model of matrix AC/DC converter is established, and themodulation algorithm, AC-DC conversion function and the regulatory function of theinput power factor is verified by this simulation.The control strategy of the matrix AC/DC converter is researched. The outputinductor current is used for the closed-loop control to realize the management of theconstant current or the constant power charge and discharge. The output capacitor voltageis used for the outer loop and the output inductor current is used for the inner loop torealize the management of the constant voltage charge. The mathematical model of theAC/DC matrix converter is established, and corresponding controller is designed. Theinfluence of the input filter is analyzed when we use the open control strategy for the inputpower factor. The corresponding closed-loop control strategy of the input power factorangle is adopted to a more accurate response. An approximate model which is verified through the simulation is build for it, and base on this model, the corresponding PIcontroller is designed.The working principle of the vanadium redox flow battery is analyzed, the simulationmodel of the flow battery is established based on the AC impedance spectroscopy, and themodel is used as a load of the AC/DC matrix converter. The simulation verified therationality of the controller both in the charge/discharge control and the input power factorangle control, and also verified that the control strategy can be used for the energymanagement of the vanadium redox flow battery energy storage system.A laboratory prototype of the AC-DC matrix converter is built for the experimentalevaluation and the lead acid battery is used as the load. The switch of the charging anddischarging experiment, the adjustment of the unit input power factor experiment and thecontrol of the power factor experiment is proposed. The result proved that the controlstrategy can be used both for the control of the battery charging/discharging and thecontrol of the input power factor angle. The rationality of this control strategy is verifiedthrough this experiment. |
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