International Journal of Scientific Engineering and Science Volume 6, Issue 10, pp. 36-45, 2022. ISSN (Online): 2456-7361 36 http://ijses.com/ All rights reserved Harmonic Effects of an OWPP Connection to Northwestern Part of Turkey-A Case Study Sehri Nur Guler 1 , Kamil Cagatay Bayindir 1 , Adnan Tan 2 1 Department of Electrical and Electronics Engineering, Ankara Yildirim Beyazit University, Ankara, Turkey, 06010 2 Department of Electrical and Electronics Engineering, Cukurova University, Adana, Turkey, 1380 Abstract— Nowadays count of Offshore Wind Power Plant investments are increasing drastically. Although Turkey is not familiar with OWPPs there is a recent tendency towards OWPPs so as to supply the increasing energy demand and meet with the lower carbon emission targets. Higher interest on larger scale OWPPs resulted in a dramatic increase in count of relevant studies. Increased harmonic introduction is considered as one of the most remarkable effects of offshore wind power plants. In terms of Turkey, Northwest part is considered as suitable for a possible OWPP connection. In order to meet grid code limits in terms of harmonics, a detailed harmonic analysis is executed for two different scenarios in case of a large scale OWPP integration. Through the analysis a frequency dependent model is employed and real voltage harmonic measurements from selected connection points is added to the developed model. Whole simulations are executed by using Power Factory Software. With this study a detailed scheme for harmonic reaction of the Turkish Transmission Network to integration of a large scale OWPP is explicitly drawn. Keywords— Harmonic distortions, Offshore wind power plants, large scale OWPPs, wind power plant grid integration, Harmonic impedance analysis, Harmonic propagation in grids, Wind turbine harmonics. I. INTRODUCTION With its high wind speed potential and remarkable location, Northwest Turkey is selected for connection of an OWPP through this study. High need of energy is a direct result of the considerable amount of industries and a crowded population living at this region. In order to supply power to these, numerous power plants are constructed at the region. A significant amount of energy is produced by wind power plants (WPPs) (approximately one fifth of monthly production [1]) at Trakya region. Count of wind power plants (WPP) at the area is increasing day by day so the percentage of wind based production is continuously improving. In terms of energy production, while some portion of energy production is made at the region, a remarkable amount of power is taken from the power plants stated at neighboring regions. This power transmission is mainly made via long high voltage overheadlines. Therefore all utilities and industries stated at the region is strongly bounded to the health and condition of these connectors. OWPPs can be a remedy to energy need at the region with their high potential of power production capability. However, connection of a large scale OWPP can be a thread for the grid tranquility unless needed analysis and plant management is done properly. Although it may be a cure to meet the energy need of the region, integration of a large-scale offshore power plant needs a strictly conducted connection analysis. This connection analysis become more crucial in terms of harmonics as there are steel industry at the region which are prone to emit harmonics. The situation is the same when the high penetration of PE-based renewable systems at the region is considered. Another important criteria for this kind of before connection analysis is the ability of simulation models to express real characteristics of the grid. In literature, in order to combat the uncertainty on reliability of simulation results, it is advised to employ frequency depended equipment models rather than lumped models [2], [3]. In terms of connection assessments must works concentrated on HVAC linked OWPPs [4], [5], [6], [7], [8], [9] rather than HVDC systems [10], [11], [12], [13] as HVAC is more matured than HVDC systems. Although it has many advantages like simpler design and lower complexity, long AC cables used in HVAC connected systems results in concerns on possible resonances and propagation of harmonic currents. High Voltage Direct Current (HVDC) based connection systems have numerous advantages like no skin effect is present for DC lines with an addition of lower losses and lower costs in manufacturing process (for lines) over High Voltage Alternating Current (HVAC) systems [14]. Inspite of these numerous features that lowering the costs, HVDC systems need a particular investment on power electronic modules. The budget needed for these modules may be more remarkable than ever with nowaday’s well-known chip crisis. Because of all given reasons above, an HVAC connection is designed instead of an HVDC system at Windflag project with the convention of keeping line lenghts low as possible (i.e by selecting a location for the OWPP close to the coasts). Therefore effects of AC cables are considered more elaborately through this study. In this work, previously produced harmonic grid model in [15] is employed for a further harmonic penetration analysis. Since the designed model have a specially selected rate of power and design traits, possible wind turbine harmonics are extracted from the literature to be modelled to the WTGs. Once the possible harmonic contribution of WTGs are decided, a statistical voltage harmonic analysis is conducted at the connection busbars. As stated in std. IEC 61000-4-30 the measured data is filtered from the flagged data then the resulting data of 2 months time period is processed. Resulting analysis are done for the cases of (1) when only background harmonic voltages taken into account, (2) when both of the