Investigation On Lightning Surge Charateristic For Wind Farm

Wind power technology has become the most widely applied renewable energy,and the 2022 Winter Olympic Games achieved 100% clean energy supply,and wind power is the most important new energy power supply means.The safe operation of wind farms is the primary requirement of wind power generation.The special structure of wind turbines and the special geographical environment of wind farms make lightning overvoltage as an important factor affecting the insulation s afety of wind farm electrical systems.This article conducts a study on the incoming lightning surge problem in onshore wind farms and offshore wind farms,mainly focusing on the impact of lightning surge on the insulation of wind farm electrical systems,and carries out insulation optimization measures to provide a theoretical basis for the lightning protection design of wind farms.Firstly,the electromagnetic transient model of wind farm electrical system under lightning overvoltage is established,the general parts of the model for onshore and offshore wind farms such as transmission lines,transmission tower,power equipment and wind turbine are developed in detail,and the differences between the two modeling parts are highlighted.The relevant calculation techniques are given for doubly-fed generators,back-to-back converter,direct-drive generators,grounding systems of mixed media and offshore substation platforms,etc.,which lay the theoretical basis for the numerical calculation of EMTP.Secondly,the effects of lightning surge overvoltage on equipment insulation in onshore wind farms are studied.The impact of lightning current waveform,lightning strike mode,lightning strike location,and wind turbine connection topology on the overvoltage caused by lightning strikes wind farm transmission line is analyzed,focusing on the differences between lightning striking the line inside the wind farm and the two cases of lightning striking the turbine blade and lightning striking the transmission line outside the wind farm substation in the wind farm,illustrating the importance of electrostatic coupling for ligtning surge transfer.The current discharge effect,energy absorption capacity and the protection distance for lightning arrester are studied in detail,and the relevant engineering recommendations for onshore wind farm lightning protection are given.In addition,the distribution of lightning surge overvoltage in offshore wind farms is studied.Offshore wind farms differ greatly from onshore wind farms.On one hand,the cable length of offshore wind farms is generally longer than onshore wind farm,approximately ten kilometers in general,and its impact on the transmission and distribution of lightning surge overvoltage is greater.On the other hand,on account of the presence of offshore substation platform,the risk of lightning strikes on wind farms,causing insulation damage to the electrical system by lightning surge overvoltage,is greatly increased.The distribution of overvoltage in the three cases of lightning strike onshore transmission tower propagated to the offshore wind farm,lightning strike on the wind turbine blade through electromagnetic coupling intrusion into the electrical system,and lightning strike on the offshore substation platform caused by the ground potential rising back flow into electric system resulting in overvoltage.Combined with the simulation calculation results to give the relevant engineering recommendations to prevent insulation damage from lingtning overvoltage,put forward two types of lightning arrester configuration schemes,and the theoretical basis is provided for offshore wind farm lightning protection.