Research On Main And Longitudinal Insulation And Leakage Magnetic Field Of ±320kV Flexible HVDC Converter Transformer

At present,the problems,such as energy shortage and environmental pollution are becoming more and more serious.Wind power,solar power and other renewable energy have been put into operation.However,these sources of energy have the characteristic of inherent dispersion,small structure,intermittence,far from the load centers,and the traditional AC and DC transmission technology both have many inherent defects for this.Therefore,the flexible HVDC transmission technology has been developing rapidly in recent years.Transformer used for Flexible HVDC project can be divided into two categories,one is called coupling transformer,another kind is called the converter transformer.Coupling transformer is similar to normal power transformer,can be manufactured according to the design principle and specification of normal power transformer.Flexible HVDC converter transformer(call it Convert Transformer in the next sentence)is similar to normal HVDC converter transformer,the DC winding is full insulation structure,stand AC voltage,DC voltage and polarity reversal voltage.This research is aimed at Flexible HVDC converter transformer.Converter transformer arranged on both ends of the flexible HVDC system in the converter station,the DC winding connected directly to the inverter,so the DC side voltage exerted on the DC winding at the same time,the electric field of converter transformer is mixed AC and DC electric field,and this is the most fundamental distinction between converter transformer and normal power transformer.At the same time,DC bias and harmonic problems occurred in the operation of the converter transformer,increase additional loss and may result in local overheating for metal structure,making it become extremely difficult and more complicated for converter transformer about insulation structure design and the control technology of leakage magnetic field.At present,the fewer flexible HVDC project is put into operation,and the voltage level and transmission capacity is small.The product for this project,DC voltage of ±320 kV,single converter transformer capacity of 176.7 MVA,product number of ZZDFPZ-176700/230-320,their level of voltage and capacity have been achieved national and the highest level in the world,and it is the leading technology innovation with difficult research and development.Based on this,on the basis of thorough investigation research,the design of the product parameters and whole insulation structure are put forward.The research for transformer insulation structure,magnetic flux leakage control and other key technologies are carried out using Main Insulation,IMV,VIT-Elmag3D finite element software.At the same time,complete the converter transformer prototype,the prototype are routine and type test to examine converter transformer overall performance,to ensure that the converter transformer technical performance parameters meet the requirements of national standards and technical agreement,making foundation for the research and development of subsequent larger capacity,higher voltage grades of flexible HVDC converter transformer.