Design Of Battery Energy Storage System Based On Partial Power Control

In the traditional battery energy storage system,the battery cell meets the demand of high voltage and large capacity through the combination of series and parallel,and then connects with the high voltage converter.Due to the differences in capacity and internal resistance between battery cells,the available capacity of different battery packs is inconsistent during charging and discharging,resulting in insufficient utilization of the overall capacity of the battery energy storage system.At present,in most flexible battery energy storage systems,the power of the system is all controlled by the charging and discharging converter,resulting in larger power and higher cost of the converter design.Aiming at the problem of unbalanced capacity and power caused by direct series and parallel connection of high-voltage large-capacity batteries and the large capacity of charging and discharging control equipment,a partial power control scheme using isolated DC/DC converter and H bridge inverter for charging and discharging control is proposed.The topology and working principle of the system are described based on the scheme adopted in this paper,and the capacity requirements of the system under various working conditions are analyzed based on the power flow direction.It is pointed out that the ratio of the power flowing through the DC/DC converter to the total output power of the battery pack is equal to the ratio of the voltage difference to the voltage ofthe DC bus.It is proved that if only part of the power is controlled in the charge and discharge control system,the whole system can operate at high power.Control the small with the big.The converter capacity is reduced.At the same time,it can control each battery independently and realize the capacity balance of battery pack and charge and discharge control ofthe system.The parallel side adopts full-bridge phase-shifted isolated DC/DC converter,and the input side is in series and the output side is in parallel,forming a parallel equalization circuit.The stable voltage control strategy is adopted to maintain the stable output voltage,and the power of the battery can be reasonably distributed according to SOC to achieve SOC balance.The parameters are calculated,the experimental platform is set up,and the simulation and experiment are used to verify.Single-phase H bridge inverter is used in series side to form the charge and discharge control circuit of the system.The rated voltage of the whole battery pack is the same as the voltage of the dc bus,but the output voltage of different SOC battery packs is different.With the three-ring control mode,only a small part of the total power of the system flows through the H bridge.The parameters were calculated,the platform was built,and the results were verified by simulation and experiment.The small signal model of isolated DC/DC converter and single-phase h-bridge inverter is established.The control parameters of DC/DC converter are designed by using zero-pole distribution diagram.The output impedance characteristics of the parallel port of the DC/DC converter and the input impedance of the h-bridge inverter are given.The stability analysis of the system is carried out by using the impedance ratio criterion,and the H bridge control parameters are given.The simulation results are verified.