Optimization Design of Stator Core Pipe for Evaporative Cooling Wind Generators Considering the Influence of Electromagnetic and Heat Transfer
Cheng Ziran1, Wang Yu2, Gao Jian1, Huang Shoudao1, Ruan Lin2,3
1. College of Electrical and Information Engineering Hunan University Changsha 410082 China; 2. Institute of Electrical Engineering Chinese Academy of Sciences Beijing 100190 China; 3. University of Chinese Academy of Sciences Beijing 100049 China
Abstract：In recent years, with the rapid development of renewable energy, the capacity of wind generators has increased, and the problems of loss and heating are becoming more and more serious. Excessive operating temperatures will harm the safe operation of wind generators. Evaporative cooling technology can greatly improve the generator’s cooling efficiency. The whole system has many advantages, such as simple maintenance, safety, reliability, and more. Many scholars have researched electromagnetic and cooling performance analysis modeling and wind generator optimization. However, the influence of small changes in the stator’s local structure on electromagnetic performance and the contact thermal resistance on cooling performance is often ignored. Therefore, a collaborative optimization strategy of electromagnetic and cooling performance is proposed based on the electromagnetic and heat transfer sensitivity analysis of the design unit. Through experiments, the thermal contact resistance between the hollow cooling tube and the core interface is measured, and the heat transfer characteristics of the hollow cooling tube under the self-circulation characteristics of a small dip angle are analyzed. The optimization design of a 10 MW direct drive wind turbine is carried out. Firstly, the influence of the stator core’s cooling pipe structure on electromagnetic and cooling performance of wind generators is analyzed based on the operating characteristics of wind generators and the element sensitivity method. Secondly, the heat transfer capacity and contact thermal resistance of hollow round copper pipe are analyzed and tested through the heat transfer experiment of self-circulating pipe with a small dip angle and the temperature rise experiment of contact thermal resistance. Thirdly, the optimization model of the stator core cooling structure is established. Finally, the optimization design of the stator core cooling structure is studied and verified by finite element analysis. The self-recirculating cooling system with a small dip angle experiment shows that the critical heat flux of a 1 500 mm hollow copper tube is 8 303 W/m2 when the condenser height is 900 mm, and the inlet temperature of cooling water is 20℃. The variation trend of the convective heat transfer coefficient of the evaporative cooling medium with heat flux is revealed by experiments, and the standard deviation of the fitted curve is 2.05. The contact thermal resistance experiment shows that when the hole/shaft matching accuracy is H7/h7, the roughness of DW470-50 is Ra3.2 μm, the heat flux is 9 549 W/m2, the contact thermal resistance between the iron core and the hollow copper tube with the roughness of Ra1.6 μm, Ra3.2 μm, and Ra 6.4 μm is 7.644 8×10-5 m2·K/W, 8.901 5×10-5 m2·K/W, and 9.425 1×10-5 m2·K/W, respectively. Finally, evaporation cooling wind generators of three different configurations using stator core pipe structures are optimized based on the sensitivity analysis strategy. The following conclusions can be drawn from the simulation analysis: (1) The established influence analysis model can analyze the influence of the stator cooling tube’s design elements on the electromagnetic and cooling performance of wind generators. (2) Based on the small-dip self-circulation test platform and the contact thermal resistance test platform, the relationship between the cooling performance of the core tube and the loaded heat flux is obtained. It shows that wind generators’ new evaporative cooling technology has good thermal conductivity. (3) The finite element simulation method verifies that the three optimization schemes can meet the requirements of electromagnetic and winding maximum temperature rise constraints.
[1] Yaramasu V, Wu Bin, Sen P C, et al.High-power wind energy conversion systems: state-of-the-art and emerging technologies[J]. Proceedings of the IEEE, 2015, 103(5): 740-788. [2] 边春元, 邢海洋, 李晓霞, 等. 基于速度变化率的无位置传感器无刷直流电机风力发电系统换相误差补偿策略[J]. 电工技术学报, 2021, 36(11): 2374-2382. Bian Chunyuan, Xing Haiyang, Li Xiaoxia, et al.Compensation strategy for commutation error of sensorless brushless DC motor wind power generation system based on speed change rate[J]. Transactions of China Electrotechnical Society, 2021, 36(11): 2374-2382. [3] 高俊国, 孟睿潇, 胡海涛, 等. 电机定子绝缘老化寿命预测研究进展[J]. 电工技术学报, 2020, 35(14): 3065-3074. Gao Junguo, Meng Ruixiao, Hu Haitao, et al.Research progress on prediction of aging life of motor stator insulation[J]. Transactions of China Electro- technical Society, 2020, 35(14): 3065-3074. [4] 丁树业, 孙兆琼, 徐殿国, 等. 3 MW双馈风力发电机传热特性数值研究[J]. 中国电机工程学报, 2012, 32(3): 137-143, 4. Ding Shuye, Sun Zhaoqiong, Xu Dianguo, et al.Numerical investigation of heat transfer for 3 MW doubly-fed wind generators[J]. Proceedings of the CSEE, 2012, 32(3): 137-143, 4. [5] 顾国彪, 阮琳. 蒸发冷却技术在水轮发电机领域的应用和发展[J]. 中国电机工程学报, 2014, 34(29): 5112-5119. Gu Guobiao, Ruan Lin.Applications and deve- lopments of the evaporative cooling technology in the field of hydrogenerators[J]. Proceedings of the CSEE, 2014, 34(29): 5112-5119. [6] 熊斌, 阮琳, 顾国彪, 等. 蒸发冷却技术在高电荷态ECR离子源磁体上的应用: LECR4[J]. 电工技术学报, 2015, 30(10): 219-225. Xiong Bin, Ruan Lin, Gu Guobiao, et al.Application of evaporative cooling technology in magnet of high charge state ECR ion source-LECR4[J]. Transactions of China Electrotechnical Society, 2015, 30(10): 219-225. [7] 张玉斌, 温英科, 阮琳. 全浸式蒸发冷却IGBT电热耦合模型研究[J]. 电工技术学报, 2022, 37(15): 3845-3856. Zhang Yubin, Wen Yingke, Ruan Lin.Research on electrothermal coupling model of fully-immersed evaporative cooling IGBT[J]. Transactions of China Electrotechnical Society, 2022, 37(15): 3845-3856. [8] 王海峰, 李旺, 顾国彪, 等. 风力发电机自循环蒸发内冷系统稳定性的研究[J]. 物理学报, 2016, 65(3): 030501. Wang Haifeng, Li Wang, Gu Guobiao, et al.Static bifurcation analysis of natural circulation inner evaporative cooling system in wind turbine[J]. Acta Physica Sinica, 2016, 65(3): 030501. [9] 高剑, 黄守道, 张文娟, 等. 基于变流器控制策略的直驱永磁风力发电机优化设计[J]. 电工技术学报, 2013, 28(7): 103-109. Gao Jian, Huang Shoudao, Zhang Wenjuan, et al.Optimal design for permanent magnet wind power generators based on converter controlling algo- rithm[J]. Transactions of China Electrotechnical Society, 2013, 28(7): 103-109. [10] McDonald A, Bhuiyan N A. On the optimization of generators for offshore direct drive wind turbines[J]. IEEE Transactions on Energy Conversion, 2017, 32(1): 348-358. [11] Bhuiyan N A, McDonald A. Optimization of offshore direct drive wind turbine generators with con- sideration of permanent magnet grade and tempera- ture[J]. IEEE Transactions on Energy Conversion, 2019, 34(2): 1105-1114. [12] Penzkofer A, Atallah K.Analytical modeling and optimization of pseudo-direct drive permanent magnet machines for large wind turbines[J]. IEEE Transa- ctions on Magnetics, 2015, 51(12): 1-14. [13] Li Wang, Wang Haifeng.Steady-state thermal simu- lation of the stator coil of the evaporative inner cooling system in wind turbines[C]//2012 IEEE 6th International Conference on Information and Auto- mation for Sustainability, Beijing, 2013: 248-251. [14] 李旺, 王海峰, 顾国彪. 风力发电机自循环蒸发内冷系统的静态分岔分析[J]. 电工电能新技术, 2015, 34(4): 6-11. Li Wang, Wang Haifeng, Gu Guobiao.Static bifurcation analysis on natural circulation inner evaporative cooling system in wind turbines[J]. Advanced Technology of Electrical Engineering and Energy, 2015, 34(4): 6-11. [15] 李伟力, 仝世伟, 程鹏. 离网型永磁同步发电机电磁场和温度场数值计算与分析[J]. 中国电机工程学报, 2010, 30(30): 107-113. Li Weili, Tong Shiwei, Cheng Peng.Calculation and analysis of electromagnetic and temperature fields in off-grid type permanent magnet synchronous gen- erator[J]. Proceedings of the CSEE, 2010, 30(30): 107-113. [16] 李伟力, 程鹏, 张美巍, 等. 1.5MW永磁风力发电机电磁场与温度场计算与分析[J]. 电机与控制学报, 2010, 14(12): 52-57, 62. Li Weili, Cheng Peng, Zhang Meiwei, et al.Electro- thermal analysis and calculation of a 1.5MW per- manent magnet wind generator[J]. Electric Machines and Control, 2010, 14(12): 52-57, 62. [17] 温彩凤, 汪建文, 孙素丽. 基于热电磁耦合的永磁风力发电机涡流损耗分析[J]. 太阳能学报, 2015, 36(9): 2278-2284. Wen Caifeng, Wang Jianwen, Sun Suli.Analysis of eddy current losses in permanent magnet wind generator based on electromagnetic-thermal coupling method[J]. Acta Energiae Solaris Sinica, 2015, 36(9): 2278-2284. [18] Cheng Ziran, Ruan Lin, Gao Jian, et al.Multi- objective optimization of stator direct cooling for direct-drive permanent-magnet wind generators[C]//2022 IEEE International Conference on Power Systems Technology (POWERCON), Kuala Lumpur, Malaysia, 2022: 1-6. [19] Cheng Ziran, Ruan Lin, Huang Shoudao, et al.Research on noise reduction of 3.6 MW evaporative cooling wind motor induced by electromagnetic and two-phase flow resonance based on stator optimi- zation[J]. Processes, 2021, 9(4): 669. [20] Yan Jing, Yu Shunzhou, Cao Rui.Research on the temperature distribution of the hollow conductors in the self-circulating evaporative inner cooling system for high power rectifier equipment[J]. Journal of Physics: Conference Series, 2021, 1748(5): 052023. [21] 窦润田, 李永建, 张献, 等. 受工艺孔影响的变压器铁心损耗计算与分析[J]. 电工技术学报, 2022, 37(12): 2909-2923. Dou Runtian, Li Yongjian, Zhang Xian, et al.Calculation and analysis of transformer core loss due to technological hole[J]. Transactions of China Electrotechnical Society, 2022, 37(12): 2909-2923. [22] 毕刘新, 王善铭, 夏永洪. 表贴式永磁电机漏磁导的解析计算[J]. 清华大学学报(自然科学版), 2010, 50(4): 525-528. Bi Liuxin, Wang Shanming, Xia Yonghong.Calcu- lation of leakage permeance in a surface-mounted permanent magnet machine[J]. Journal of Tsinghua University (Science and Technology), 2010, 50(4): 525-528. [23] 杨世铭, 陶文铨. 传热学[M]. 4版. 北京: 高等教育出版社, 2006. [24] 骆凯传, 师蔚, 张舟云. 基于温度实验的永磁同步电机损耗分离方法[J]. 电工技术学报, 2022, 37(16): 4060-4073. Luo Kaichuan, Shi Wei, Zhang Zhouyun.Method of loss separation of permanent magnet synchronous motor based on temperature experiment[J]. Transa- ctions of China Electrotechnical Society, 2022, 37(16): 4060-4073. [25] Liu Chengsi, Xu Yongxiang, Zou Jibin, et al.Permanent magnet shape optimization method for PMSM air gap flux density harmonics reduction[J]. CES Transactions on Electrical Machines and Systems, 2021, 5(4): 284-290. [26] 佟文明, 姚颖聪, 李世奇, 等. 考虑磁桥不均匀饱和的内置式永磁同步电机等效磁网络模型[J]. 电工技术学报, 2022, 37(12): 2961-2970. Tong Wenming, Yao Yingcong, Li Shiqi, et al.Equivalent magnetic network model for interior permanent magnet machines considering non-uniform saturation of magnetic bridges[J]. Transactions of China Electrotechnical Society, 2022, 37(12): 2961-2970. [27] 刘硕, 方国东, 王兵, 等. 近场动力学与有限元方法耦合求解热传导问题[J]. 力学学报, 2018, 50(2): 339-348. Liu Shuo, Fang Guodong, Wang Bing, et al.Study of thermal conduction problem using coupled peridy- namics and finite element method[J]. Chinese Journal of Theoretical and Applied Mechanics, 2018, 50(2): 339-348. [28] 鲁钟琪. 两相流与沸腾传热[M]. 北京: 清华大学出版社, 2002. [29] Sigmund O, Petersson J.Numerical instabilities in topology optimization: a survey on procedures dealing with checkerboards, mesh-dependencies and local minima[J]. Structural Optimization, 1998, 16(1): 68-75. [30] 国建鸿, 傅德平, 袁建华, 等. 300MW汽轮发电机强迫循环蒸发冷却定子绕组温升计算[J]. 中国电机工程学报, 2008, 28(26): 92-97. Guo Jianhong, Fu Deping, Yuan Jianhua, et al.Calculation of temperature distribution of larger evaporative cooling turbo-generator with forced inner cooling system[J]. Proceedings of the CSEE, 2008, 28(26): 92-97. [31] 李晔, 李琦, 范涛, 等. 电传动车辆用永磁电机定子绕组等效导热系数获取方法[J]. 兵工学报, 2021, 42(10): 2215-2222. Li Ye, Li Qi, Fan Tao, et al.Acquisition method for equivalent thermal conductivity coefficient of stator winding of permanent magnet motor[J]. Acta Armamentarii, 2021, 42(10): 2215-2222.
2024, Vol. 39 
