Fault detection in Multi-Terminal Modular Multilevel Converter (MMC) based High Voltage DC (HVDC) transmission system

Abstract

A Multi-Terminal High Voltage Direct Current (MT-HVDC) network is being considered for utilising the full potential of offshore wind power whereas its realisation is currently being hampered by protection issues. In this paper, a protection strategy for future DC grids based on Modular Multilevel Converter (MMC) based HVDC system is presented. Firstly, a fault detection technique based on initial / measurement is presented and thereafter protection strategies for future DC grids are presented. The fault detection technique presented is based on estimating the initial rate of rise of the current, ( / ) at fault inception using measured data and thereafter calculating the line inductance. The calculated line inductance is compared with a setting value to determine whether or not a fault has occurred, thus paving the way for a distance protection strategy. Simulations were carried out using Matlab/SIMULINK for varying fault distances. The results obtained show the validity of the technique in detecting and locating DC side short circuits. An advantage of this technique is that it relies only on information from the local end terminal and as such, no communication channel is required, hence satisfying the protection requirement of fast fault detection and location technique for MT-HVDC systems.

Protection Systems for Multi-Terminal HVDC Grids

“…Therefore, the non-unit protection is usually a preferred option for MTDC grids, but with some limitations since it cannot guarantee absolute selectivity. Therefore, in the context of future MTDC grids, the non-unit protection may be used as the main protection and unit protection may serve as a backup [23].…”

Transient‐based protection technique for future DC grids utilising travelling wave power

“…The availability of fast fault detection algorithms is a prerequisite for the secure and reliable operation of multi‐terminal HVDC systems also termed DC grids [1–8]. This is because DC fault current rises rapidly due to the low inductance in DC systems compared with AC systems, thus reaching damaging levels in a few milliseconds [2].…”

A novel time domain protection technique for multi-terminal HVDC networks utilising travelling wave energy

“…The availability of fast fault detection algorithms is a prerequisite for the secure, safe and reliable operation of Multi-terminal HVDC systems (or DC grids) [1,2]. Although several attempts have been made in recent past to develop DC line protection algorithms for DC grids [3][4][5][6][7][8][9][10][11][12][13][14][15][16], however, trends and recent advances made in the development of DC grids still create opportunities for further research and studies in DC grid protection. Generally, DC fault current rises rapidly due to the low reactance in DC systems compared to AC systems, thus reaching damaging levels in a few milliseconds [2].…”