Abstract

Flexible direct current (DC) transmission network technology is an effective method for large capacity clean energy access to power grids, but the DC short-circuit fault detection for it is a difficult problem. In this paper, the pole-to-ground fault transient characteristics in a multi-terminal DC power grid, based on overhead transmission lines and DC circuit breakers, are analyzed firstly. Then, a fast protection scheme is proposed according to the fault transient characteristics. Only local information is utilized for fault detection and location in the proposed scheme. Moreover, the scheme is verified to have the advantages of fast action speed, high reliability and the ability to resist the transition resistance. A four terminal DC power grid model based on actual engineering parameters is established in PSCAD/EMTDC, and the validity of the protection scheme under different fault conditions is verified by simulation results.

Highlights

  • Modular multilevel converters (MMCs) and their significant advantages have been widely studied since 2002 [1,2,3,4]

  • High voltage direct current (HVDC) systems based on MMC are being used in more and more power transmission projects all over the world [5,6]

  • MMC-HVDC demonstration project based on overhead transmission lines is under construction in Zhangbei, China

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Summary

Introduction

Modular multilevel converters (MMCs) and their significant advantages have been widely studied since 2002 [1,2,3,4]. High voltage direct current (HVDC) systems based on MMC are being used in more and more power transmission projects all over the world [5,6]. The influence of different pole-to-ground faults in DC power systems. Thefaults influence different topologies on the characteristics topologies on thefaults characteristics of pole-to-ground faults fault was current introduced in [21]. The configuration of MMC during pole-to-ground faults is given in [24], but the fault pole-to-ground faults is given [24], but the fault current equivalent circuit is not mentioned. In this this paper, paper, the the pole-to-ground pole-to-ground fault fault transient transient characteristics characteristics are are analyzed analyzed in in detail detail first.

MMC-MTDC System and Simulation
Pole-To-Ground Fault
Pole-To-Ground
Grounding
Single-Terminal
Sub-Module
Transmission
Transmission Lines Discharge Current ifgc
Multi-Terminal
Protection Scheme
Protection Start-up Unit
Determination of the Fault Type and Faulty Poles
Fault Location Discrimination
Protection Threshold Setting and Sensitivity Analysis of Internal Fault
Protection
Fault Resistance
19. When the fault distance are curve
Conclusions

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