{"id":336,"date":"2016-05-30T12:28:18","date_gmt":"2016-05-30T11:28:18","guid":{"rendered":"http:\/\/lukasz.kocewiak.eu\/blog\/?p=336"},"modified":"2016-05-30T12:28:18","modified_gmt":"2016-05-30T11:28:18","slug":"wind-turbine-harmonic-model-some-considerations","status":"publish","type":"post","link":"https:\/\/lukasz.kocewiak.eu\/blog\/2016\/05\/30\/wind-turbine-harmonic-model-some-considerations\/","title":{"rendered":"Wind Turbine Harmonic Model - Some considerations"},"content":{"rendered":"

Nowadays large offshore wind power plants (WPPs) are complex structures including wind turbines (WTs), array cable systems, and HVAC or HVDC offshore\/onshore transmission systems. This represents new challenges to the industry in relation to prediction and mitigation of harmonic emission and propagation\u00a0[1]. Due to increasing complexity of WPPs it is more and more important to appropriately address harmonic analysis of WTs as well as WPP on a system level by means of modelling during the design stage as well as harmonic evaluation during operation.<\/p>\n

Harmonic current emissions from the WT are strongly dependent on the WT internal impedances as well as the external network frequency-dependent short circuit impedance.\u00a0Unfortunately until now there has been no systematic approach to represent a WT from its harmonic performance perspective. This brings inconsistency in WT harmonic performance assessment, evaluation of background distortion in grid-connected WT and harmonic analysis of WPPs.<\/p>\n

Due to the different approaches in electrical design taken by WT manufacturers it is convenient to represent WT harmonics in a generic way by means of a Th\u00e9venin equivalent circuit comprising an ideal voltage source and an equivalent impedance. Such an equivalent circuit is to be provided for each harmonic component of interest to be included in the model.\u00a0Therefore using the WT harmonic model, as either Norton or Th\u00e9venin equivalent circuits, in simulations with commonly used engineering tools one can estimate the harmonic contribution to the system to which it is connected [2]. WTs as a part of a WPP system can be potentially considered as harmonic sources as well as harmonic mitigation units by means of active and passive filtering thus the structure of the harmonic model should reflect that behavior, e.g. harmonic source and equivalent impedance adjusted accordingly to active filter software settings, equivalent impedance adjustment if the WT passive harmonic filter is incorporated in it.<\/p>\n

According to Th\u00e9venin's (or Norton\u2019s) theorem any linear electrical network with voltage and current sources and only impedances can be replaced at the terminals of interest by an equivalent voltage source VTh<\/sup><\/em> in series connection (or an equivalent current source INo<\/sup><\/em> in parallel connection) with an equivalent impedance Zth<\/sup><\/em> (or ZNo<\/sup><\/em>, where ZTh<\/sup><\/em> = ZNo<\/sup><\/em>). Th\u00e9venin's theorem is dual to Norton's theorem and is widely used for circuit analysis simplification and to study the circuit initial-condition and steady-state response.<\/p>\n

\"Wind<\/a><\/p>\n

[1]\u00a0\u0141.\u00a0H.\u00a0Kocewiak, J.\u00a0Hjerrild, and C.\u00a0Leth Bak, \u201cWind Turbine Converter Control Interaction with Complex Wind Farm Systems<\/a>,\u201d IET Renewable Power Generation<\/i>, Vol.\u00a07, No.\u00a04, 2013.<\/p>\n

[2]\u00a0\u0141.\u00a0H.\u00a0Kocewiak, C.\u00a0\u00c1lvarez, P.\u00a0Muszynski, J.\u00a0Cassoli, L.\u00a0Shuai, \u201cWind Turbine Harmonic Model and Its Application \u2013 Overview, Status and Outline of the New IEC Technical Report<\/a>,\u201d in Proc. The 14th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as Transmission Networks for Offshore Wind Farms<\/i>, Energynautics GmbH, 20-22\u00a0October\u00a02015, Brussels, Belgium.<\/p>\n