طراحي سيستم قدرت يكپارچه DC براي كلكتور نيروگاه هاي بادي فراساحل متصل به شبكه

چكيده انگليسي :

108 Pure DC Collector System Design for Grid connected Offshore Wind Farms Shadi Chuang pishet s chuangpishet@ec iut ac ir Date of Submission August 2011 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language PersianSupervisor Ahmadreza Tabesh a tabesh@cc iut ac irAbstract Emerging offshore wind farms capable of massive scale energy production have directed researchactivities toward wind power technologies well suited for offshore applications Increasing the size ofoffshore wind farms imposes challenges regarding feasibility of conventional ac power transmission andcollector systems The main reasons are the high charging current of ac submarine cables and increasingsystem losses Recent studies have identified pure dc systems including dc transmission and collectorsystems as a promising solution for grid integration of distant offshore wind farms Using a dc systemovercomes power losses and reactive power requirements which conventionally associate with submarinepower cables employed in ac systems This thesis investigates pure dc systems for offshore applications and proposes a modeling and controlapproach besides an appropriate topology for the collector system of an offshore wind farm The collectorsystem of an offshore wind farm consists of all equipment within the wind farm to a collection point including the wind turbine generators transformers power electronics and all existing cable connections First through investigation of different wind energy systems a dc based offshore wind farm has beenconsidered consisting of permanent magnet synchronous generators diode bridge rectifiers and dc dcconverters Such integration offers a robust structure well suited for offshore wind power applications Asimplified yet accurate model for a wind power unit is proposed and validated which is useful for controllerdesign to capture the maximum wind power of the unit A control technique is also presented and itsperformance has been investigated based on sensitivity analysis and time domain simulation of a studysystem The results of analysis show an accurate tracking performance with less than 1 error when the windspeed varies about 25 of its rated value The sensitivity analysis also confirms the robustness of thecontrol system against model uncertainties which can arise from the aging phenomenon of the units Secondly a matrix interconnected topology has been proposed and investigated for collector system of anoffshore wind farm The topology is based on the series parallel layout in which some switches are locatedbetween adjacent branches The possibility to change the system structure using the inter branch switchesmitigates the overvoltage problem of the units on failure occurrences providing maximum available powerfor the whole wind farm This leads to considerable increase in the system reliability and efficiency Based onfailure coverage capability the operating area of matrix interconnected method has been evaluated andcompared to that of the short circuit method The study shows that increasing the number of branchesaugmented to the faulty branch extends the matrix method operating area This analysis also suggests acriterion for the branch number in a dc collector system in order to have a full coverage of failure occurrencesby matrix interconnected method This criterion might be useful in collector system design purposes Finally a study system consisting of 12 wind turbine generator units has been simulated and investigated fordifferent failure occasions The dc switch costs and the additional control complexities are counted as thedrawbacks of the matrix interconnected topologyKeywords Collector systems DC power systems Offshore wind farm Pure dc systems Wind energy systems Wind turbine generator

چوانگ پيشت، شادي

طراحي سيستم قدرت يكپارچه DC براي كلكتور نيروگاه هاي بادي فراساحل متصل به شبكه

توربين-ژنراتوربادي , مدل سازي ديناميكي , مزارع باد , كنترل نيروگاه هاي بادي