Analysis of the Influence of Impedance Characteristics of Traction Network on the Stability of Vehicle Energy Storage System and Compensation Strategy

Abstract

With the development of traction power supply system of rail transit in the direction of high efficiency and intelligence, the role of vehicle energy storage system in improving energy utilization rate and mitigating power grid impact has become increasingly prominent. However, the interaction between the impedance characteristics of the traction network and the control dynamics of the energy storage system is easy to cause low frequency oscillation and resonant instability, which restricts the stable operation of the energy storage system. In this paper, the coupling stability of traction network and energy storage system is the core of the research. Firstly, the frequency domain impedance model of traction network is established considering the parameter distribution characteristics, and the validity of the model is verified by the measured data. Through multi-time scale coupling analysis, the influence mechanism of impedance characteristics on the control bandwidth and modal damping of the energy storage system is revealed. It is found that the negative damping effect of traction network impedance is the key factor leading to the resonant frequency deviation of the system. To solve these problems, an active damping control strategy based on virtual impedance injection is proposed, and a collaborative compensation framework combining online impedance identification and model prediction is designed. Simulation and hardware-in-the-loop experiments show that the proposed strategy can effectively suppress system oscillation and improve the stability of the energy storage system in the wide band domain. The research results provide theoretical support for the engineering design of vehicle energy storage system, and have important reference value for the optimization of intelligent traction power supply system.