Wenji Song

Study on the model of elevator regeneration energy and its energy storage control method

The battery energy storage system (BESS) insisting of Li4Ti5O12 (LTO)-based batteries is put forward in this paper in order to suppress the voltage fluctuation of the DC grid of elevator caused by regeneration energy of the traction machine. Based on the mathematical model of the regenerative power set up in MatLab/Simulink, the capacity and control method of BESS is designed to effectively achieve the absorption and release of the regeneration energy. Moreover, a dynamic control strategy is researched to improve its applicability in actual system. The simulation results show that BESS could well restrain the grid voltage within the safety working range and availably reduce the total energy consumption of the elevator.

Investigation on dynamic equalisation performance of lithium battery pack management

Lithium batteries must be connected in series to achieve large capacity and high-power output. Battery management system (BMS), which is designed to protect battery pack from damage and increase battery life, is important in electrical power system. The present equalisation techniques have many disadvantages: The passive balancing wastes energy and generates heat, while active balancing is complex. This study proposes an intelligent BMS with dynamic equalisation (DBMS) which contains active and passive balancing circuit independently per cell. Experimental results indicate that DBMS can reduce the inconsistency among cells. Moreover, the DBMS can assist battery stack to store and release more energy. Besides, the battery stack with DBMS gives an energy efficiency of 96.5% which is 7.7% higher than that without balancing. In addition, the battery stack with DBMS can reduce the maximum state of charge difference of cells from 10.415% to 4.51% after three charge-discharge cycles. What is more, the DBMS is simple and can decrease the auxiliary power level and the system heat. Such a DBMS will help us to provide a high-performance battery pack.

Development of supervising system for battery energy storage system based on the two-level architecture

The real-time monitoring of status parameters, such as cell voltage and state of charge (SOC), is an important guarantee of the safety operation of the battery energy storage system (BESS). And the two-level architecture of hardware system which includes several battery management units (BMU) and the central management unit (CMU) is designed with the communication protocol and data conversion algorithm for achieving the data acquisition and communication. Moreover, an enhanced SOC method involving the resting time and the terminal voltage is researched and programmed in the software system. The battery supervising system is verified by lots of experiments that it could satisfy the monitoring demand of BESS and has improved the accuracy of SOC estimation effectively.

Simulation Research on Voltage Stabilization Control Strategy for Rail Transportation Traction Grid Based on HESS

In order to realize the voltage stabilization of rail transportation traction grid efficiently, a hybrid energy storage system (HESS) composed of lithium batteries and supercapacitors is presented for application in the DC power supply system to absorb and release the regenerative braking energy. Through studying the coordination control strategy of HESS, the control models are set up and simulated in MATLAB/Simulink. It can be seen from the simulation results that the control strategy makes the HESS well stabilize the traction grid voltage within an appropriate operating range. Moreover, the battery pack and the supercapacitor pack are both used in their optimal working states, causing the HESS to recycle the braking energy availably and satisfy the purposes of clean energy and green travel of rail transportation commendably.

Research on the capacity of hybrid energy storage system and its control method in rail transit traction grid

The hybrid energy storage system (HESS) composed of super capacitors and batteries is proposed in this paper for the power supply system of rail transmit to prevent the overtension of grid voltage caused by the braking energy. According to the power fluctuations and allocation principle, the capacity and control method of HESS are designed to achieve the voltage stabilization of the traction grid as well as the proportion optimization between super capacitors and batteries. The simulation results show that HESS could restrain the voltage within the safety operating range and effectively reduce the redundant capacity and cost of the system.