基于智能优化算法的高频变压器电磁结构优化设计

Optimization Design of Electromagnetic Structure of High Frequency Transformer Based on Intelligent Optimization Algorithm

高频变压器(HFT)作为电力电子变换器等功率变换装备的核心部件,其优化设计是实现高功率密度、高效率和高可靠性的重要环节。为有效解决高频条件下显著的涡流效应和复杂紧凑的结构使变压器损耗难以准确计算、针对绝缘设计裕量不足的问题,本文提出计及高频效应和结构效应的电磁场建模方法,构建了高频变压器多目标协同优化设计方案。首先建立了低成本与高效率兼备的磁心损耗计算模型。其次,根据面积等效原理推导了考虑绕组结构效应的近似Dowell模型,实现绕组损耗的高精度计算。然后提出了考虑绕组端部效应和频率影响的漏感计算模型,减小漏感对于结构和频率的依赖性。在此基础上,采用一种新型多重绝缘结构,提高绕组间的绝缘耐压水平。最后,基于改进的非支配排序遗传算法(INSGA-Ⅱ)和自由参数扫描法建立了高频变压器的优化设计流程,根据筛选的最优设计方案研制了一台高频变压器样机。

As a core component in power conversion fields such as power electronic transformers(PET),the optimal design of high-frequency transformers(HFT)has become essential to achieving high power density,high efficiency,and high reliability.However,the significant eddy current effect and complex and compact structure under high-frequency conditions make it challenging to accurately calculate transformers’losses and insufficient insulation design margins.Meanwhile,the multiple optimization objectives of HFT are mutually constrained yet difficult to balance,which brings severe challenges to electromagnetic design.Therefore,an electrical and magnetic field modeling method based on the analysis of high-frequency and structure effects is proposed,and a design scheme for multi-objective collaborative optimization of HFT is constructed.A core loss calculation model with low cost and high efficiency is established by fitting the complex integral function in IGSE under high-frequency non-sinusoidal excitation waveform.The calculation results of the magnetic core loss are consistent with the finite element simulation results.To achieve high-precision calculation of winding losses,an approximate Dowell model,which takes account of the structure effect and eddy current effect of windings,is derived according to the equivalence principle of area,and the impact of winding structure on winding losses is weakened.Compared with the finite element simulation results,the errors in the calculation and measurement results of winding losses of this model are all within acceptable ranges.A leakage inductance calculation model is presented considering the winding edge effect and frequency effect to reduce the dependence of leakage inductance on structure and frequency.Detailed electromagnetic finite element analysis,derivation,and experimental verification are conducted on this model,indicating that this model can accurately calculate the total leakage inductance of high-frequency transformers.To reduce the risk of insulation reliability degradation caused by thermal aging and other issues during the operation of high-frequency transformers,a novel multiple dielectric structure upgrades the insulation to withstand voltage levels between windings,considering long-term and short-term dielectric strength.At the same time,the maximum electric field strength is verified to be within a reliable safety margin through finite element simulation.The algorithm of NSGA-Ⅱis improved by introducing dynamic clustering distance and arithmetic crossover operator,which is tested using ZDT1 and ZDT3 functions.The effectiveness of the improved scheme is verified using a mathematical model for high-frequency transformer optimization design.Finally,combined with the INSGA-Ⅱwith the free parameter scanning method,the optimization design process of HFT is established,and an HFT prototype is manufactured based on the selected optimal design.Under no-load conditions,the magnetic core loss and temperature rise of the prototype are measured.The experimental results show that the error between the measurement and simulation results of the magnetic core loss is small,and the temperature rise meets the expected design requirements without thermal operation problems.