全直流海上风电场的损耗计算及大功率中频变压器的设计

发布时间：2018-04-10 12:38

本文选题：直流海上风电场 + 传统海上风电场　；参考：《浙江大学》2017年硕士论文

【摘要】：为了减少温室效应,降低碳排放量,风力发电、生物能、太阳能等可再生能源的开发利用成为近十年能源研究和发展重点。风力发电经历了从小规模至大规模、从内陆拓展至海上、从高压交流输电至高压直流输电的阶段。由于海上风电场具有风力资源丰富且稳定、不占用土地、可以大规模开发等优势,且随着电力电子技术和高压直流输电技术的发展,海上风电场的研究获得了飞速发展。已建成的海上风电场均采用交流汇集-直流传输结构,为了进一步降低风电场的建设成本、减小风机变流平台的体积和重量、减少风电传输并网损耗和提高设备的工作效率,纯直流海上风电场已成为研究热点,鉴于直流风电场尚处于理论研究阶段,高压大容量关键设备的研究以及风电场的损耗分析具有重要意义。本文提出了一种基于模块化隔离型DC/DC变换器(Modular isolated DC/DC converter,MIDC)的直流风电场拓扑,并考虑直流风电场中的实际情况,对中频变压器进行了详细的分析和设计。针对变压器原副边绕组自身绝缘要求较低,而绕组之间的绝缘要求较高的特殊情况,设计了一种采用高压电缆作为高压侧绕组的中频同轴变压器。然后建立了变压器优化设计的数学模型,提出了此种变压器的优化设计流程。本文以额定容量250kVA的中频同轴变压器为例,绘制了不同参数下,变压器的体积和功率密度分布图,Ansys软件仿真验证了优化结果的可行性,最后考虑到实际工程中电缆的最小弯曲半径要求,对变压器的设计思路进行了补充说明,形成了完整的中频同轴变压器的设计方案。为了分析和比较风电场的系统损耗,本文以MMC-HVDC的传统海上风电场和模块化隔离型DC/DC变换器的海上直流风电场为例,计算了额定容量为400MW的两种风电场的平均损耗和器件数量。在实际海上风电场中,由于风速具有随机性和不稳定性,为使风电场的损耗计算具有实际意义,本文定义了风电场的平均损耗。然后针对两种风电场的结构,分别对其系统损耗进行了分类,并对风电场中所应用的设备进行了参数设计、器件选型和损耗计算。理论计算结果表明:传统海上风电场和直流风电场的平均损耗分别为4.0%和2.12%,直流风电场中整流二极管的数目有所增加,但却有效降低了系统中IGBT的数量,且模块化结构有利于降低器件的电压等级和电流等级,IGBT的成本得以降低。本文根据实际应用需求,一方面对一种适用于MIDC的中频同轴变压器进行了研究和设计,仿真验证了设计结果的有效性;另一方面详细分析和比较了两种风电场的系统损耗和器件数量,为今后直流海上风电场的样机研制和工程应用提供详实的理论基础。
[Abstract]:In order to reduce Greenhouse Effect, reduce carbon emissions, wind power, biomass, solar energy and other renewable energy development and utilization has become the focus of energy research and development in the past decade.Wind power generation has experienced a period from small scale to large scale, from inland to offshore, from HVAC to HVDC.Offshore wind farms have the advantages of abundant and stable wind resources, no land occupation, and can be developed on a large scale. With the development of power electronics technology and HVDC transmission technology, the research of offshore wind farms has been rapidly developed.In order to further reduce the construction cost of wind farm, reduce the volume and weight of fan converter platform, reduce the loss of wind power transmission and grid connection and improve the working efficiency of the equipment, all the offshore wind farms have been constructed with AC converging-DC transmission structure, so as to further reduce the cost of wind farm construction, reduce the volume and weight of fan converter platform.Pure DC offshore wind farm has become a research hotspot. In view of the fact that the DC wind farm is still in the theoretical research stage, it is of great significance to study the key equipment of high voltage and large capacity and to analyze the loss of wind farm.This paper presents a DC wind farm topology based on modular isolated DC/DC converter Modular isolated DC/DC converter MIDC. Considering the actual situation of DC wind farm, the if transformer is analyzed and designed in detail.In view of the special situation that the insulation requirement of the primary and secondary side windings of the transformer is low and the insulation requirements between the windings are high, a kind of intermediate frequency coaxial transformer with high voltage cable as the high voltage side winding is designed.Then the mathematical model of optimal design of transformer is established, and the flow of optimal design of this kind of transformer is put forward.Taking if coaxial transformer with rated capacity 250kVA as an example, the volume and power density distribution diagram of transformer is drawn under different parameters. The simulation results of Ansys software verify the feasibility of the optimization results.Finally, considering the requirement of minimum bending radius of cable in practical engineering, the design idea of transformer is supplemented, and a complete design scheme of if coaxial transformer is formed.In order to analyze and compare the system losses of wind farms, the average loss and the number of devices of two wind farms with rated capacity of 400MW are calculated by taking the traditional offshore wind farm of MMC-HVDC and the offshore DC wind farm of modular isolated DC/DC converter as examples.In the actual offshore wind farm, due to the randomness and instability of wind speed, in order to make the calculation of wind farm loss have practical significance, this paper defines the average loss of wind farm.Then according to the structure of two kinds of wind farm, the system loss is classified, and the parameters design, device selection and loss calculation of the equipment used in the wind farm are carried out.The theoretical calculation results show that the average losses of conventional offshore wind farm and DC wind farm are 4.0% and 2.12% respectively. The number of rectifier diodes in DC wind farm is increased, but the number of IGBT in the system is reduced effectively.And the modularization structure can reduce the cost of IGBT.According to the practical application requirements, on the one hand, a kind of if coaxial transformer suitable for MIDC is studied and designed, and the validity of the design result is verified by simulation.On the other hand, the system loss and the number of devices of the two kinds of wind farms are analyzed and compared in detail, which provides a detailed theoretical basis for the prototype development and engineering application of DC offshore wind farms in the future.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614;TM432

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