【时  间】2023年11月22日   下午:14:00-15:20

【地  点】北京校区  主楼D260会议室



李泽元教授(Fred C. Lee)于1968年在台湾国立成功大学获得电气工程学士学位,随后于1972年和1974年分别在杜克大学获得电气工程硕士和博士学位。李泽元教授是弗吉尼亚理工大学的名誉特聘教授,也是弗吉尼亚理工大学电力电子研究中心(CPES)的创始人和名誉主任。作为CPES的学术带头人,李教授主持了一系列项目,涵盖了研究、技术开发、教育推广、产业合作和技术转移。CPES致力于满足行业需求,推动其研究和成果应用于产业。迄今为止,全球超过250家公司受益于该研究中心的产业合作项目。由于其在产业合作、技术转移、教育和推广等方面的贡献,CPES被美国国家科学基金会(NSF)评为模范工程研究中心(ERC)。李教授的研究方向为高频功率变换、磁性和电磁干扰、分布式电力系统、可再生能源、电能质量、以及高密度电子封装、集成、建模和控制。李教授拥有107项美国专利,并发表了超过340篇期刊论文和790多篇经过评审的技术论文。在弗吉尼亚理工大学任职期间,李教授指导了90名博士和94名硕士学生完成学业。李教授是美国国家工程院院士、中国工程院外籍院士。根据Research.com网站上的D-Index排名,李教授是电子与电气工程学科的世界顶尖学者之一。

Fred C. Lee received his B.S. degree in electrical engineering from the National Cheng Kung University in Taiwan in 1968, and his M.S. and Ph.D. degrees in electrical engineering from Duke University in 1972 and 1974, respectively.Dr. Lee is a University Distinguished Professor Emeritus and Founder and Director Emeritus of CPES, a preeminent academic center in power electronics research at Virginia Tech.  As CPES Director, Dr. Lee led a program that encompasses research, technology development, educational outreach, industry collaboration, and technology transfer.  CPES focuses its research on meeting industry needs and allows industry to benefit from the Center's research and outputs.  To date, more than 250 companies worldwide have benefited from the industry partnership program.  The center has been cited by NSF as a model ERC for its industry collaboration and technology transfer, education, and outreach programs.Dr. Lee's research interests include high-frequency power conversion, magnetics and EMI, distributed power systems, renewable energy, power quality, high-density electronics packaging and integration, and modeling and control.Dr. Lee holds 107 U.S. patents and has published over 340 journal articles and over 790 refereed technical papers.  During his tenure at Virginia Tech, Dr. Lee has supervised to completion 90 Ph.D. and 94 Master's students.Dr. Lee is a member of the U.S. National Academy of Engineering, and a foreign member of the Chinese Academy of Engineering in the People’s Republic of China.  According to Research.com D-Index ranking, Dr. Lee is among the world’s top scholars within the discipline of Electronics and Electrical Engineering.



Modular multilevel converter is deemed the key interface technology between renewable energy sources and the existing utility power grids. However, the interface control currently deployed is rather complicated and counterintuitive. Since the systems states are far greater than the means of control, the extend of control to minimize the circulating energy was rather ambiguous. Without proper modeling and control, this system is often operated with large circulating energy, resulting in excessive use of the bulky energy storage capacitors.

Employing state-plane analysis techniques, two types of circulating energies are delineated graphically, one related to the energy exchange between input and output, and the other related to the energy swapping between upper arm and lower arm. Furthermore, these two power flows are orthogonal in nature, implying that the means of control for each power flow path are independent. Consequently, a coordinate transformation is employed, leading to a decoupled equivalent circuit model. Each power flow path is governed by it’s own control law. Methods of eliminating circulating energy are clearly identified.