| In recent years,with the development of battery energy storage technology,the energy storage capacity of the battery and the required charging rate are becoming more and more diverse.This requires the battery charging system to cover a wider range of output power.In addition,in different energy storage situations,the power supply voltage of the charging system is different,from hundreds of volts to thousands of volts.Therefore,the charging system is also required to adapt to a wider range of power supply.If the MOSFET with high power and high voltage level is adopted,its comprehensive performance is poor.The modular input series output parallel technology is an effective way to solve the problem of expanding the capacity of the charging system while reducing the withstand voltage level of the converter and giving full play to the performance advantages of the low voltage MOSFET.Therefore,study ISOP charging system,solve the problem of input voltage sharing in charging system,and achieve no interconnection between charging modules have great theoretical and practical significance to improve the flexibility of the capacity expansion of the charging system.Therefore,a modular ISOP charging system with no interconnected control is proposed in this paper.Using standardized charging module to achieve flexible input series output parallel combinationcan meet different input voltage requirements and meet different output power level requirements.Each standardized module in the charging system includes the charging unit and the auxiliary power unit.The charging unit of the charging module of the ISOP charging system combined the ISOP charging unit circuit.The charging unit adopts unit output current control,and the ISOP charging unit circuit with unit output current control has the constant output current input series output independent characteristic.The auxiliary power units in the charging module form the SIMO unit combination circuit,which has an input series output independent constant output voltage characteristic.In order to achieve input voltage sharing(IVS)between the charging units and IVS between the auxiliary power supply units when the charging system works in standby conditions,and input voltage,the stable operation condition of the DC/DC system with input series output independent characteristic is studied.And the stability criterion is given from the angle of output voltage disturbance and input voltage disturbance,respectively.Utilizing stability criterion,the stability of the common independent output voltage / current control method is analyzed.Based on that,a unit input voltage control method is put forward,which lays a foundation for realizing the no interconnection control between the standard charging modules composed by charging units and auxiliary power units.In order to achieve IVS and constant current output of ISOP charging unit,a distributed output current compensation control strategy is proposed.Based on the small signal model of the the full bridge charging unit and the proposed control strategy,the closed-loop transfer function of the output current control loop and the IVS control loop are obtained.Using the Hurwitz criterion obtaines the controller stability parameter interval,proves the effectiveness of the proposed control strategy.On this basis,the design principles of the control loop are given,and according to the design principle,the controller parameters are designed under the condition of resistance and battery load respectively,which shows its universality different load occasions.In addition,due to the output current control loop in each charge unit,each charge unit can work independently.For SIMO unit circuit,in order to achieve IVS and improve the universality of the circuit structure,the non isolated SIMO unit circuit is studied,and a distributed dynamic IVS control strategy is proposed.Through the distributed master-slave control between each unit,IVS is realized,and there is no interconnection between units.Based on the Buck small signal model,the stability of the control strategy is analyzed,and the design principle is given.Through the analysis of the steady-state output voltages of each unit shows that if the distributed dynamic IVS control SIMO unit circuit is used as the auxiliary power can meet the power supply requirements.According to the power supply requirements of each charging unit,the isolated flyback SIMO auxiliary power supply is studied.The distributed dynamic IVS control strategy is used to solve the IVS problem in the process of standby conditions.Meanwhile,according to the characteristics of flyback circuit,the control strategy is improved.And peak current distributed dynamic IVS control strategy is proposed,which realizes decoupling design between the master and slave auxiliary power units.The ISOP charging unit circuit and the flyback SIMO auxiliary power are combined to design a prototype of the two module ISOP charging system.The systme is tested with two 12V/120 AH series lead-acid battery pack.Considering the interaction between the IVS control of the charging unit and the auxiliary power supply,the charging system is improved.On the basis of the improved charging system,the charging program is designed according to the four stage charging curve.It verifies the effectiveness of the modular ISOP charging system and its related control strategies. |
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