A hierarchical coordinated control strategy based on multi-port energy router of urban rail transit

Abstract

The multi-port energy router (ER) is an effective topology for integrating train traction load, AC load, the energy storage system and photovoltaic(PV) energy. The start and stop process of urban rail transit trains and the access of distributed energy sources to rail transit ER lead to serious fluctuations of DC bus power, so it is necessary to route energy between different ports, involving multi-operating modes, while seamless switching is a major challenge. In this paper, a hierarchical coordinated control strategy is proposed to enable the multi-port ER to operate in a coordinated fashion under the conditions of train parking, acceleration, constant power driving and deceleration, and to switch seamlessly under various working conditions. The energy central dispatching layer sends working condition instructions by sampling the state information of each port, while the microgrid control layer adopts centralized control, receiving upper working condition instructions and sending drive signals to the local control layers to maintain the balanced energy flow of each port. In the local control layers, the PV adopts the improved perturbation and observation method of power control (PC-P&O), while the ES system adopts voltage loop control with an SOC influence factor, voltage loop control with switching factor and power loop control according to the different working conditions, so as to transmit the required train load power accurately and maintain the stability of the DC bus voltage. Finally, the effectiveness of the proposed hierarchical coordination control is verified by MATLAB/Simulink simulations.