Impact of Inverter-Based Resources on Negative Sequence Quantities-Based Protection Elements

Abstract

Inverter-Based Resources (IBRs), including Wind turbine generators (WTGs), exhibit substantially different negative-sequence fault current characteristics compared to synchronous generators (SGs). These differences may cause misoperation of customary negative-sequence-based protective elements set under the assumption of a conventional SG dominated power system. The amplitude of the negative-sequence fault current of a WTG is smaller than that of an SG. This may lead to misoperation of the negative-sequence overcurrent elements 50Q/51Q. Moreover, the angular relation of the negativesequence current and voltage is different under WTGs, which may result in the misoperation of directional negative-sequence overcurrent element 67Q. This paper first studies the key differences between the WTGs and SG by comparing their equivalent negative-sequence impedances with SG's. Then, simulation case studies are presented showing the misoperation of 50Q and 67Q due to wind generation and the corresponding impact on communication-assisted protection and fault identification scheme (FID). The impact on directional element is also experimentally validated in a hardware-in-the-loop real-time simulation set up using a physical relay. Finally, the paper studies the impact of various factors such as WTG type (Type-III/Type-IV) and Type-IV WTG control scheme (coupled/decoupled sequence) to determine the key features that need to be considered in practical protection studies. The objective is to show potential protection misoperation issues, identify the cause, and propose potential solutions.

Impact of DFIG‐based wind turbine's fault current on distance relay during symmetrical faults

“…Building on the analysis above, further work will concentrate on the following points. (i) To evaluate the actual repossess and performances of commercial protective relays with real‐time and hardware in the loop tools [27]. (ii) To analyse the impacts of DFIG‐based WT's fault current on the performances of a distance relay during unsymmetrical faults and grid code [28].…”

Impact of Inverter Based Resources on System Protection

“…Quad ground distance element also uses negative-sequence quantities [38,39] but is not considered in detail in this paper. References [8,15,16,18,25,26] have studied potential misoperation scenarios for these schemes due to IBRs. These misoperation issues originate from two key differences between the fault current characteristics of IBRs and conventional SGs, namely lower amplitude and changed phase angle of I2.…”

“…A potential solution to these misoperation problems is to require I2 control by IBRs during an unbalanced fault. The German grid code is an example of such a requirement, and it has been shown to be capable of resolving the misoperation issues in some cases [25,26].…”

“…The discrepancy in the amplitude of sequence currents is due to modeling differences and unavailability of the full data of the system. The Recommendation-Potential solutions to this misoperation include: (i) use of directional zero sequence elements instead of directional negative sequence elements for ground fault protection (assuming the IBR to be connected through a transformer that is a source of I0) [26]; (ii) IBR reactive I2 injection under unbalanced faults (e.g., per the German grid code) [25,26].…”

“…Several references have studied the performance of protective relay schemes under IBRs including line distance protection [6][7][8][9][10][11][12][13]16,18], negative sequence components based protection [8,[15][16][17][18][19][20][21][24][25][26], communication-assisted protection [15,24,25], fault identification (FID) [15,24,25], rate-of-change-of-frequency (ROCOF), and power swing protection [14,16,27]. This paper reviews the key findings of these studies; further, the paper studies for the first time the performance of memory-polarized directional overcurrent protective relay elements, line current differential (LCD) protection, and phase comparison (PC) protection under IBRs.…”