Wind farms should contribute to power system control (voltage and frequency) and also to the electricity network recover in case of networks faults such as voltage dips or swells. In the most cases a wind turbine should work with a power factor of 0.90 lagging to 0.95 leading and the frequency should situate within the range from 47.5 Hz to 52 Hz. The most outstanding international Grid Codes are the following:
• USA FERC: "Interconnection for Wind Energy" 18 CFR Part 35 (Docket No. RM05-4-001; Order No. 661-A), Issued December 12, 2005 and "Interconnection Requirements for a Wind Generating Plant", Appendix G to the LGIA.
• Germany - E.ON Netz GmbH: "Grid Code - High and extra high voltage", Status: 1.April 2006.
• China - CEPRI: "Technical Rule for Connecting Wind Farm to Power System", December, 2005.
• Spain - REE - P.O. 12.3: Resolución de 4 de octubre de 2006, de la Secretaría General de Energía por la que se aprueba el procedimiento de operación 12.3 "Requisitos de respuesta frente a huecos de tensión de las instalaciones eólicas". Publicación en BOE núm. 254 de fecha 24 Octubre 2006.
• India - ISTS: "Indian Electricity Grid Code (IEGC)", April, 2006 and "Draft Report on Indian Wind Grid Code", July, 2009.
• France: "Décret no 2GGS-SS6 du 2S avril 2GGS relatif aux prescriptions techniques générales de conception et de fonctionnement pour le raccordement d'installations de production aux réseaux publics d'électricité", April, 2008.
• Italy: "CEI 11-S2; V1 Impianti di produzione eolica", December, 2006.
• Great Britain - National Grid Electricity Transmission plc: "The Grid Code", Issue 4 Revision 3, 6th September 2010.
• Denmark - ELKRAFT SYSTEM and ELTRA: "Wind Turbines Connected to Grids with Voltages above 1GG kV - Technical regulations for the properties and the regulation of wind turbines", Regulation TF 3.2.5, December 3, 2004.
• Portugal - REN: Portaria n.° 596/2010 de 30 de Julho
• Canada - AESO: "Wind Power Facility - Technical Requirements", Revision 0, November, 15 2004.
• Australia - AEMC: "National Electricity Rules (NER)", Version 39, 16 September 2010
• Ireland - EIRGRID: "WFPS1- Controllable Wind Farm Power Station Grid Code Provisions", EirGrid Grid Code, Version 3.4, October 16th 2009.
Fault ride through requirements are described by a voltage vs. time characteristic, denoting the minimum required immunity of the wind power station. The fault ride through requirements also include fast active and reactive power restoration to the prefault values, after the system voltage returns to normal operation levels. Some codes impose increased reactive power generation by the wind turbines during the disturbance, in order to provide voltage support, a requirement that resembles the behaviour of conventional synchronous generators in over-excited operation.
Fig. 1 presents in the same graph the fault ride through requirements from the different Grid Codes. These requirements depend on the specific characteristics of each power system and the protection employed and they deviate significantly from each other.
Fig. 1. Fault ride through requirements.
FERC (us*) -ELKRAFT&ELTRA (DEN) Svensko Kroftnät (SWE)
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