Research On Dynamic Threshold Control Strategy Of Urban Rail-to-Surface Lithium Battery Energy Storage System Based On Double Extended Kalman Filter

The rapid development of urban rail transit makes its energy consumption problems become prominent.Making full use of train regenerative braking energy can significantly reduce the output energy consumption of traction substations,which is an effective way to reduce the overall energy consumption of urban rail transit.The use of energy storage devices to recover the regenerated energy not only avoids the regenerative energy being consumed in the form of heat energy but also improves the DC net pressure fluctuation,which is a hot topic in the field of rail transit in recent years.The control strategy proposed in this paper needs the real-time SOC value of the energy storage system.For this reason,we choose the double extended Kalman filter witch with high accuracy.Through the established battery model,real-time observation of the system SOC is realized.The optimal SOC working range of the energy storage system is obtained from the battery characteristics test.By designing a dynamic threshold control strategy based on SOC,the goal of controlling the energy storage system in its optimal SOC range is achieved.The strategy is divided into three control intervals according to the system SOC value:the first interval the SOC follows the high reference value when the system SOC is low by adjusting the discharge threshold;the second interval is the threshold control interval,when the system SOC is between the limit value;the third interval is low SOC track control interval,the strategy of this interval is the same the first interval,but the reference value lower.Through the partition control can avoid the SOC overshoot caused by PI regulation.The DEKF SOC estimate and proposed control strategy is verified by experimental.The platform mainly includes two parts:the motor platform and energy storage system platform.The motor platform can simulate the running conditions of the train to provide the load for the energy storage system platform.The energy storage system platform mainly consists of lithium titanate battery energy storage module and bidirectional DC/DC converter.The proposed control strategy can be realized by DC/DC.At last,the dynamic threshold control strategy is verified by the cycling condition test.