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• Accordingly, a flexible traction power supply system (FTPSS) composed of a TT and multi-port power hub and its coordinated control strategy are proposed for VU compensation and energy conservation in this paper. The main contributions can be summarized as follows: • Different from previous research, a power hub is installed in the TPSS to achieve power flow control among the utility grid, traction network, and DC grid. The FTPPS with the power hub can enable VU compensation for the utility grid, which also offers a friendly interface with distributed PV and ESS for on-site access. • A three-port VU compensation method based on active power flow control and reactive power injection is presented, which divides the system demand compensation capacity and reduces the performance requirements for power electronics, compared with traditional compensation methods. • A coordinated control strategy with a hierarchical structure is designed for FTPSS. The control strategy enables real-time power management to enhance energy utilization and mitigate VU in the system layer and coordinates multiple converters to realize the multi-function operation of the system in the converter layer. To mitigate voltage unbalance (VU) and eliminate the neutral sections while reducing the energy consumption of railways, a flexible traction power supply system (FTPSS) with the power hub is proposed. Different from conventional schemes, the proposed system provides a friendly interface to realize the on-site access of distributed photovoltaic (PV) generation along the railway line and concentrated integration of energy storage systems. The power flow is centrally managed by the power hub to reduce energy consumption and the proposed three-port VU compensation method is coupled with the power hub to suppress negative sequence current caused by trains. Considering the volatility of PV generation and traction loads, four operation modes including grid-connected, valley filling, VU compensation, and peak clipping mode, are proposed to dynamically regulate the operation of FTPSS. Moreover, a coordinated control strategy with a hierarchical structure is developed to enable the operation modes. The strategy is implemented with a global controller and multiple local controllers, which can realize real-time power management and flexible transition among different modes. Finally, different simulation and experimental case studies based on the field data are carried out to comprehensively verify the feasibility and effectiveness of the proposed FTPSS and control strategy. [ABSTRACT FROM AUTHOR]