A Decentralized Coordinated Control Strategy for Multiple Traction Substations in MVdc Railway Power Supply System

The 24-kV medium-voltage direct current (MVdc) railway power supply system (RPSS) is a promising candidate for future high-speed railways. In this article, to achieve the coordinated operation of multiple traction substations (TSSs) in the system, a decentralized coordinated control strategy with the capabilities to simultaneously enhance the system stability, guarantee the train's regenerative braking ability, and satisfy the plug-and-play requirement of TSSs is proposed. First, in the outer control loop of the TSS, the virtual inertia control (VIC) strategy, which can provide inertia support to the system, is adopted to achieve decentralized voltage regulation and power sharing control among the multiple TSSs. Meanwhile, to guarantee the train's regenerative braking ability, the TSS's dc-link voltage reference generated by the VIC is further limited to a constant value when the train's braking power makes the TSS's output voltage greater than a certain value. In addition, a presynchronization control strategy is also designed to interact with the VIC to satisfy the TSS's plug-and-play requirement. Then, in the inner voltage and current control loop of the TSS, to achieve fast dc-link voltage tracking and simplify the inner loop control system structure, a composite control strategy based on model predictive control (MPC) and extended stated observer (ESO)-based improved dynamic reference designed (IDRG) method is employed. Finally, numerous simulation results of 24-kV MVdc RPSS conducted in MATLAB/Simulink are provided to verify the effectiveness of the proposed control strategy.