Journal of Modern Power Systems and Clean Energy

ISSN 2196-5625 CN 32-1884/TK

Adaptive droop control for better current-sharing in VSC-based MVDC railway electrification system
Author:
Affiliation:

1. College of Electrical Engineering, Southwest Jiaotong University, Chengdu, China; 2. National Rail Transit Electrification and Automation Engineering Technique Research Center, Southwest Jiaotong University, Chengdu, China

Fund Project:

‘‘the Open Project of National Rail Transit Electrification and Automation Engineering Technique Research Center’’ (No. NEEC-2017-A03), and partly supported by ‘‘the Fundamental Research Funds for the Central Universities’’ (No. 2682017CX041).

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    Abstract:

    The share of voltage source converter (VSC) technology is increasing in conventional power systems, and it is penetrating into specific transportation systems such as electric vehicles, railways, and ships. Researchers are identifying feasible methods to improve the performance of railway electrification systems (RESs) by utilizing VSC-based medium-voltage direct current (MVDC) railways. The continuous motion of electric trains makes the catenary resistance a variable quantity, as compared to the traction substation (TSS), and affects the current-sharing behavior of the system. A modified droop control technique is proposed in this paper for VSC-based MVDC RES to provide more effective current-sharing while maintaining catenary voltages above the minimum allowable limit. The droop coefficient is selected through an exponential function based on the ratio between the concerned TSS current and the system average current. This enables small adjustments of droop values in less concerning marginal current deviations, and provides higher droop adjustments for large current deviations. Meanwhile, the catenary voltages are regulated by considering the voltage data at the midpoint between two TSSs, which experiences the lowest voltages owing to the larger distance from the TSSs. The proposed techniques are validated via simulations and experiments.

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History
  • Received:
  • Revised:
  • Adopted:
  • Online: July 31,2019
  • Published: