Parallel Operation Control Strategy Of Power Converter Systems For Lead-Carbon Batteries

Lead-carbon batteries with the characteristics of lead-acid batteries and supercapacitors have been widely used because of their great potential in the field of battery energy storage..The control strategy of power converter system(PCS)is the core of grid-connected operation of the lead-carbon battery energy storage system(lead-carbon BESS).In large capacity BESS,the parallel structure of PCS is used to increase the capacity of BESS.At present,the topology of multi-PCS parallel operation lead-carbon BESS is complex.And the circulating current and current sharing among the parallel operation units seriously affects the stability of the system.Therefore,it is of practical significance to study the integration and control of multi-PCS.In this paper,the working principle of lead-carbon BESS was analyzed.Based on the ideal switching function of power switch,the mathematical model of lead-carbon BESS was established,and the characteristics of the model were analyzed.The topology of parallel system was analyzed,and the best parallel topology of lead-carbon BESS was selected according to the characteristics of lead-carbon BESS parallel operation.The selection basis of the number and connection mode of lead-carbon battery pack was given.In order to meet the grid-connected and BESS operation requirements of power fluctuation,current ripple,voltage overshoot and dynamic response,the parameters of DC side inductance,LCL filter and DC side capacitance were designed.Based on the characteristics of lead-carbon BESS,the control strategy of single lead-carbon BESS were designed to realize the grid-connected charging and discharging.The mechanism of current sharing in parallel operation lead-carbon BESS was analyzed.The advantages and disadvantages of current sharing control strategies were summarized.Aiming at the shortcomings of current sharing control strategies,an improved current sharing control strategy was proposed to improve the current sharing of the parallel operation systems.Finally,a simulation platform of lead-carbon BESS was built based on PSCAD/EMTDC.The simulation experiments included charging and discharging simulation experiments of single lead-carbon BESS,charging and discharging simulation experiments of parallel operation lead-carbon BESS and current sharing simulation experiments in impedance mismatch.The purpose of the experiment was to verify the charging and discharging ability of the lead-carbon BESS designed in this paper and the current sharing of the parallel operation system.