Distributed Battery Energy Storage System Design And Control Of DBESS

As an essential part of grid-friendly generation technologies,the energy storage system(ESS)has promising application prospects for supporting photovoltaic,integrating renewable energies,improving grid safety,and prolonging the upgrade of electrical equipment.Along with the increasing number of electric vehicles,a large number of retired batteries come out,and the GWh era will come in 2019.However,since the retired vehicle battery still has utilization value,how to realize second use in power grid is an urgent problem to be solved.Considering the above background,this thesis takes the power conversion system(PCS)and battery management system(BMS)as the key points,and carries out related research,in order to improve the cycle life of retired batteries and reduce waste.Firstly,the dq mathematical model and soft phase-locked loop(SPLL)model of three-phase voltage source PWM rectifier(VSR)are established.Based on the synchronous rotating coordinate system,the active and reactive power control of VSR is realized by voltage feedforward decoupling method.The linearized buck/boost small-signal model is established to analyze the factors affecting the DC bus voltage stability.Then,the droop control strategy considering the battery's differential characteristics is proposed.The soft-start circuit and its control procedure are presented in detail.The feasibility and effectiveness of the proposed control strategy is verified on Matlab/Simulink.Secondly,combined with the former research,the concept and principle of dynamic reconfigurable battery(DRB)system grouping is overviewed briefly,of which the advantages and disadvantages are analyzed.The influence of battery cell series and parallel characteristics on battery grouping is simulated and analyzed.Then,the battery pack made by cells in series and group-to-group reconfigurable system topology is designed.Considering the cell-level and group-level,the DRB management system is designed based on mealy-finite state machine,and the delicacy management strategy was proposed,which combines the active group equalizer with the passive cell one.Finally,the prototype is designed,whose hardware circuit and software of PCS and DRB systems were described in detail.SEMIKRON and INFINEON IGBTs are used as power modules,and 18650 lithium batteries are used to create the 3kW ESS prototype.The PCS and DRB system operation status are uploaded to the upper monitor through RS-485 series bus to verify the improvement of the ESS with proposed strategies.