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Protection of Transmission Lines Connected to Wind Farms Including Type 4 Wind Generator Turbines

Keyshams, Arash | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58750 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Hajipour, Ehsan; Ravanji, Mohammad Hassan
  7. Abstract:
  8. Renewable energy sources, as a sustainable alternative to fossil fuels, have increasingly attracted the attention of governments and international organizations in recent years. A significant share of these sources is inverter-based resources (IBRs), whose behavior differs fundamentally from that of synchronous generators due to the inherent limitations of power electronic converters. The control strategies implemented in inverters and their semiconductor-based nature typically restrict fault current injection to about 1.1 to 1.5 per unit. This behavioral difference introduces new complexities in the field of power system protection and highlights the necessity of revisiting conventional protection schemes. In this research, the main focus is on the challenges associated with longitudinal transmission line differential protection (87L) in systems connected to IBRs. Differential protection is considered one of the most reliable protection schemes for transmission lines due to its zone-based operating principle and its relative independence from fault current magnitude. However, the presence of inverter-based resources can adversely affect the performance of the external fault detection (EFD) logic. Under single-line-to-ground (SLG) fault conditions, owing to the fundamentally different behavior of inverter-based resources compared to synchronous sources—which typically inject high fault currents with well-defined negative- and zero-sequence components consistent with fault characteristics—the injection of negative- and zero-sequence components by IBRs is limited or even completely suppressed. Consequently, restraining currents in the healthy phases may increase. This phenomenon can cause the relay to incorrectly interpret the event as an external fault in the healthy phase and issue a blocking command for a predefined time interval. As a result, the correct operation of the differential relay during internal faults may be compromised. To analyze this issue, inverter-based resources and the study network were modeled in detail. The modeling incorporates the control loops of grid-following (GFL) inverters and is implemented under both coupled- and decoupled-sequence control modes. Validation was performed against the requirements of the grid code and the IEEE 2800-2022 standard. Subsequently, the behavior of the differential relay was simulated and assessed under various fault scenarios, with particular emphasis on SLG faults in the presence of IBRs. The results demonstrate that the inherent fault current limitation of IBRs can lead to maloperation of the EFD logic and reduce the reliability of the 87L protection scheme. Based on these findings, this thesis proposes an enhanced approach that leverages simple yet analytically consistent formulations aligned with realistic network conditions. The proposed method improves the performance of 87L protection in IBR-integrated systems without imposing significant computational complexity
  9. Keywords:
  10. Renewable Energy Resources ; Institute Electrical and Electronic Engineers (IEEE)2800-2022 Standard ; Low Voltage Ride Through (LVRT) ; Fault-Ride Through ; Wind Farms ; Inverter Based Distributed Generation ; Grid Following ; External Fault Detection (EFD) ; Line Differential Protection

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