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.