Yuzhang Lin

  • Assistant Professor

Electrical and Computer Engineering

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Yuzhang LIN

Dr. Yuzhang Lin is an Assistant Professor in the Department of Electrical and Computer Engineering at NYU Tandon School of Engineering. He was an Assistant Professor in the Department of Electrical and Computer Engineering at the University of Massachusetts Lowell since 2018.

Dr. Lin obtained his Ph.D. degree from Northeastern University, Boston, MA, and his B.Eng. and M.S. degrees from Tsinghua University, Beijing, China. His research interests focus on smart grid and renewable energy, especially in the aspects of modeling, situational awareness, cyber-physical resilience, and machine learning  applications. He publishes widely in the top journals of the domain, and also serves as an Editor/Reviewer for many journals and conferences. He serves as the Co-chair of the IEEE PES Task Force for Standard Test Cases for Power Systems State Estimation, and the Secretary of IEEE PES Distribution System Operation and Planning Subcommittee. He is a recipient of the prestigious Graduate Student Outstanding Research Award at Northeastern University, Boston, MA. His research is funded by NSF, DOE, and ONR. He is a recipient of the NSF CAREER Award.

Research Interests
Smart power grid and renewable energy systems: modeling, situational awareness, cyber-physical resilience, and machine learning applications
  • Ph.D., Electrical Engineering, Northeastern University, Boston, MA, USA, 2018.
  • M.S., Electrical Engineering, Tsinghua University, Beijing, China, 2014.
  • B.Eng., Electrical Engineering, Tsinghua University, Beijing, China, 2012.
  • Assistant Professor, Department of Electrical and Computer Engineering, New York University, 09/2023 - present.
  • Assistant Professor, Department of Electrical and Computer Engineering, University of Massachusetts Lowell, 09/2018 - 08/2023.

IEEE Services

  • Secretary, IEEE PES Distribution System Operation & Planning Subcommittee 
  • Co-chair, IEEE PES Task Force on Standard Test Cases of Power System State Estimation

 Editorial and Reviewing Services

  • Associate Editor, IET Generation, Transmission & Distribution
  • Subject Editor, CSEE Journal of Power and Energy Systems
  • Guest Editor, Research Topic “Data-driven Decision Making for Decarbonized Power System,” Frontiers in Big Data
  • Guest Editor, Research Topic “Exploring Cyber-Physical Interactions in Energy and Power Systems: Theory and Application,” Frontiers in Energy Research
  • Guest Editor, Special Issue “Situational Awareness of Integrated Energy Systems,” IET Generation, Transmission & Distribution
  • Guest Editor, Special Section “State Estimation for Future Cyber-Physical Power and Energy Systems: Challenges and Solutions,” Journal of Modern Power Systems and Clean Energy
  • Book Proposal Reviewer, IET
  • Book Proposal Reviewer, Springer
  • Paper Reviewer, IEEE Transactions on Smart Grid, IEEE Transactions on Power Systems, IEEE Transactions on Sustainable Energy, IEEE Transactions on Power Delivery, IEEE Power Engineering Letters, IEEE Transactions on Industrial Informatics, IEEE Transactions on Industrial Applications, IEEE Transactions on Industrial Electronics, IEEE Transactions on Industrial Electronics, IEEE Transactions on Control Systems Technology, IEEE Transactions on Control of Network Systems, IEEE Journal of Selected Topics in Signal Processing, IEEE Internet of Things Journal, IEEE Access, IET Generation, Transmission & Distribution, IET Renewable Power Generation, International Journal of Electrical Power and Energy Systems, Electric Power Systems Research, CSEE Journal of Power and Energy Systems, Energies, IEEE PES General Meeting, IEEE Powertech Conference, Power System Computation Conference (PSCC)

Conference Services

  • Workshop Co-Chair, Learning and Optimization for Power Distribution System Resilience,  IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm), 2023
  • Technical Program Committee Member, IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm), 2022
  • Technical Program Committee Member, IEEE Global Communications Conference (GlobeCom), 2021, 2022, 2023
  • Panel Chair, IEEE PES General Meeting, Data-Driven State and Parameter Estimation in Power Distribution Systems, 2022

Funding Agency Services

  • Panelist, NSF Energy, Power, Control, and Networks (EPCN) Program
  • Panelist, NSF Addressing Systems Challenges through Engineering Teams (ASCENT) program
  • Reviewer, Mitacs Accelerate
  • Technical Committee Working Group Recognition Award for Outstanding Technical Report, IEEE Power & Energy Society
  • Outstanding Reviewer Award, IEEE Transactions on Power Systems, 2023.
  • NSF CAREER Award, NSF Energy, Power, Control, and Networks (EPCN) Program, 2022.
  • Outstanding Reviewer Award, IEEE Transactions on Power Systems, 2022.
  • Outstanding Reviewer Award, IEEE Transactions on Power Systems, 2021.
  • Best Reviewer Award, IEEE Transactions on Smart Grid, 2019.
  • Outstanding Graduate Student Research Award, Northeastern University, 2018.
  • Outstanding Undergraduate Thesis, Department of Electrical Engineering, Tsinghua University, 2012.

Group Members

  • Md. Zahidul Islam, Ph.D. Student
  • Heqing Huang, Ph.D. Student
  • Wentao Zhang, Ph.D. Student
  • Guibin Chen, Ph.D. Student
  • Haoyang Li, Master Student
  • Shamsun Nahar Edib, Ph.D. Student (At UMass)
  • Nitish Sharma, Ph.D. Student (At UMass)
  • Kenneth Watts, Ph.D. Student (At UMass; Co-Advised)

Group Alumni

  • Avinash Kumar, Postdoc Research Associate (At UMass)
  • Gang Cheng, Ph.D. Student (At UMass)
  • Musaab Mohammed Ali, Master Student (At UMass; With Master Thesis)
  • Habibat Olaide Alimi, Master Student (At UMass)
  • Edwin Meriaux, Undergraduate Student (At UMass; Co-Advised)
  • David Koehler, Summer Intern (At UMass; Co-Advised; Undergraduate at Wentworth Institute of Technology)
  • Nan Feng, Senior Design Advisee (Undergraduate at University of Cincinnati)

* Corresponding author.

Book Chapters

  • Y. Lin*, Y. Liu, X. Lu, and H. Huang, “State and parameter estimation for microgrids,” Microgrids: Theory and Practice, IEEE Press. (scheduled to be published in 2023)
  • Y. Lin*, V. M. Vokkarane, M. Z. Islam, and S. N. Edib, “Resilient sensing and communication architecture for microgrid management,” Microgrids: Theory and Practice, IEEE Press. (scheduled to be published in 2023)
  • Y. Liu, Y. Lin, and K. Yue, “Modern power system state estimation methods,” Encyclopedia of Electrical and Electronic Power Engineering, Elsevier, 2022.
  • A. Abur, M. Gol, and Y. Lin, “Estimating the system state and network model errors,” Advanced Data Analytics for Power Systems, Cambridge U. Press, 2021.
  •  Y. Liu, Y. Lin, and J. Zhao, “Advanced grid operational tools based on state estimation,” New Technologies for Power System Operation and Analysis,  Academic Press, 2021.

Journal Publications

  • H. Huang, Y. Lin*, X. Lu, Y. Zhao, and A. Kumar, “Dynamic state estimation for inverter-based resources: a control-physics dual estimation framework,” IEEE Transactions on Power Systems. (accepted)
  • M. Z. Islam, Y. Lin*, V. M. Vokkarane, and N. Yu, “Robust learning-based real-time load estimation using sparsely deployed smart meters with high reporting rates,” Applied Energy. (accepted)
  • H. Huang, Y. Lin*, Y. Zhou, Y. Zhao, P. Zhang, and L. Fan, “Data-driven modeling of power system dynamics: challenges, state of the art, and future work,” iEnergy. (accepted)
  • G. Cheng, Y. Lin*, A. Abur, A. Gomez-Exposito, and W. Wu, “A survey of power system state estimation using multiple data sources: PMUs, SCADA, AMI, and beyond,” IEEE Transactions on Smart Grid. (early access)
  • S. N. Edib, Y. Lin*, V. M. Vokkarane, F. Qiu, Y. Zhang, and P. Du, “Situation-aware load restoration considering uncertainty and correlation,” IEEE Transactions on Power Systems. (early access)
  • G. Cheng, Y. Lin*, J. Yan, J. Zhao, and L. Bai, “Model-measurement data integrity attacks,” IEEE Transactions on Smart Grid. (early access)
  • M. Z. Islam, S. N. Edib, V. M. Vokkarane, Y. Lin*, and X. Fan, “A scalable PDC placement technique for fast and resilient monitoring of large power grids,” IEEE Transactions on Control of Network Systems. (early access)
  • K. Sun, M. Huang, Z. Wei, Y. Lin, and G. Sun, “Local hybrid linear state estimation for electric power systems using stream processing,” CSEE Journal of Power and Energy Systems. (early access)
  • W. Zhang, S. Song, Y. Lin*, C. Wang, and Y. Chen, “Multi-source-data state estimation for integrated electricity-heat-building networks,” Sustainable Energy, Grids and Networks, vol. 36, art no. 101131, Dec. 2023.
  • S. N. Edib, Y. Lin*, V. M. Vokkarane, F. Qiu, R. Yao, and B. Chen, “Cyber restoration of power systems: concept and methodology for resilient observability,” IEEE Transactions on Systems, Man, and Cybernetics: Systems, vol. 53, no. 8, pp. 5185-5198, Aug. 2023.
  • M. Z. Islam, Y. Lin*, V. M. Vokkarane, and V. Venkataramanan, “Cyber-physical cascading failure and resilience of power grid: a comprehensive review,” Frontiers in Energy Research, vol. 11, art no. 1095303, Feb. 2023.
  • S. Song, W. Zhang, Y. Lin*, and C. Wang, “Thermo-electrical state and demand response potential estimation for power systems with building thermostats,” International Journal of Electrical Power and Energy Systems, vol. 145, art no. 108588, Feb. 2023.
  • S. N. Edib, Y. Lin*, V. M. Vokkarane, X. Fan, "A cross-domain optimization framework of PMU and communication placement for multi-domain resiliency and cost reduction," IEEE Internet of Things Journal, vol. 10, no. 9, pp. 7490-7504, May 2023.
  • Y. Jia, Y. Liu, B. Wang, D. Lu, and Y. Lin, “Power network fault location with exact distributed parameter line model and sparse estimation,” Electric Power Systems Research, vol. 212, art no. 108137, Nov. 2022.
  • S. Song, H. Xiong, Y. Lin*, M. Huang, Z. Wei, Z. Fang, “Robust three-phase state estimation for PV-integrated unbalanced distribution systems,” Applied Energy, , vol. 306, part B, art no. 119427, Sep 2022.
  • C. Liu, C. Wang, Y. Lin, and T. Bi, “Robust unit commitment of integrated electric-heat systems with weather parameter driven uncertainties,” IEEE Systems Journal, vol. 16, no. 3, pp. 4641-4652, Sep 2022.
  • G. Cheng, Y. Lin*, J. Zhao, and J. Yan, “A highly discriminative detector against false data injection attacks in AC state estimation,” IEEE Transactions on Smart Grid, vol. 13, no. 3, pp. 2318-2330, May 2022.
  • S. Song, H. Wei, Y. Lin*, C. Wang, and A. Gomez-Exposito, “A holistic state estimation framework for active distribution networks with battery energy storage systems,” Journal of Modern Power Systems and Clean Energy, vol. 10, no. 3, pp. 627-636, May 2022.
  • Z. Fang, Y. Lin*, S. Song, C. Li, X. Lin, F. Wang, and Y. Lu, “A comprehensive framework for robust AC/DC grid state estimation against measurement and control input errors,” IEEE Transactions on Power Systems, vol. 37, no. 2, pp. 1067-1077, Mar 2022.
  • M. Huang, Z. Wei, and Y. Lin, “Forecasting-aided state estimation based on deep learning for hybrid AC/DC distribution systems,” Applied Energy, vol. 306, part B, art no. 118119, Jan 2022.
  • Y. Chen, Y. Yao, and Y. Lin, “Dynamic state estimation for integrated electricity-gas systems based on Kalman filter,” CSEE Journal of Power and Energy Systems, vol. 8, no. 1, pp. 293-303, Jan 2022.
  • Z. Li, J. Liu, Y. Lin*, and F. Wang, “Grid-constrained data cleansing method for enhanced bus load forecasting,” IEEE Transactions on Measurement and Instrumentation, vol. 70, art no. 9002810, 2021.
  • Y. Chen, H. Chen, Y. Jiao, J. Ma, and Y. Lin, “Data-driven robust state estimation through off-line learning and on-line matching,” Journal of Modern Power Systems and Clean Energy, vol. 9, no. 4, pp. 897-909, Jul. 2021.
  • G. Cheng, Y. Lin*, Y. Chen, T. Bi, “Adaptive state estimation for power systems measured by PMUs with unknown and time-varying error statistics,” IEEE Transactions on Power Systems, vol. 36, no. 5, pp. 4482-4491, Sep 2021.
  • S. Song, P. Wu, Y. Lin*, and Y. Chen, “A general dynamic state estimation framework for monitoring and control of permanent magnetic synchronous generators-based wind turbines,” IEEE Access, vol. 9, pp. 72228-72238, 2021.
  • S. N. Edib, Y. Lin*, V. M. Vokkarane, F. Qiu, R. Yao, and D. Zhao, “Optimal PMU restoration for power system observability recovery after massive attacks,” IEEE Transactions on Smart Grid, vol. 12, no. 2, pp. 1565-1576, Mar 2021.
  • Z. Fang, Y. Lin*, S. Song, C. Li, X. Lin, and Y. Chen, “State estimation for situational awareness of active distribution system with photovoltaic power plants,” IEEE Transactions on Smart Grid, vol. 12, no. 1, pp. 239-250, Jan 2021.
  • Y. Lin, A. Abur, and H. Xu, “Identifying security vulnerabilities in electricity market operations induced by weakly detectable network parameter errors”, IEEE Transactions on Industrial Informatics, vol. 17, no. 1, pp. 627-636, Jan 2021.
  • Z. Zhen, J. Liu, Z. Zhang, F. Wang, H. Chai, Y. Yu, X. Lu, T. Wang, and Y. Lin, “Deep learning based surface irradiance mapping model for solar PV power forecasting using sky image,” IEEE Transactions on Industry Applications, vol. 56, no. 4, pp. 3385-3396, Jul. 2020.
  • Y. Lin*, A. Abur, and H. Xu, “Secure market operation in the presence of critical model parameters in state estimation,” Journal of Modern Power Systems and Clean Energy, vol. 8, no. 4, pp. 699-708, Jul 2020.
  • C. Wang, C. Liu, Y. Lin*, and T. Bi, “Day-ahead dispatch of integrated electric-heat systems considering weather-parameter-driven residential thermal demands,” Energy, vol. 203, Jul 2020.
  • H. Xu, Y. Lin*, X. Zhang, and F. Wang, “Power system parameter attack for financial profits in electricity markets”, IEEE Transactions on Smart Grid, vol. 11, no. 4, pp. 3438-3446, Jul 2020.
  • S. Song, Z. Wei, Y. Lin*, B. Liu, and H. Liu, “Impedance modeling and stability analysis of PV grid-connected inverter system considering frequency coupling,” CSEE Journal of Power and Energy Systems, vol. 6, no. 2, pp. 279-290, Jun 2020.
  • Z. Fang, Y. Lin*, S. Song, C. Song, X. Lin, and G. Cheng, “Active distribution system state estimation incorporating photovoltaic generation system model,” Electric Power Systems Research, vol. 182, May 2020.
  • G. Cheng, S. Song, Y. Lin, Q. Huang, X. Lin, and F. Wang, “Enhanced state estimation and bad data identification in active power distribution networks using photovoltaic power forecasting,” Electric Power Systems Research, vol. 177, Dec 2019.
  • Z. Fang, S. Song, Y. Lin, X. Lin, G. Cheng, “State estimation for active distribution systems incorporating photovoltaic plant and battery energy storage system,” Automation of Electric Power Systems, vol. 43, no. 13, pp. 71-79, Jul 2019.
  • Y. Lin and A. Abur, “A highly efficient bad data identification approach for very large scale power systems,” IEEE Transactions on Power Systems, vol. 33, no. 6, pp. 5979-5989, Nov 2018.
  • Y. Lin and A. Abur, “Robust state estimation against measurement and network parameter errors,” IEEE Transactions on Power Systems, doi. vol.33, no.5, pp.4751-4759, Sep 2018.
  • Y. Lin and A. Abur, “Strategic use of synchronized phasor measurements to improve network parameter error detection,” IEEE Transactions on Smart Grid, vol. 9, no. 5, pp. 5281 – 5290, Sep 2018.
  • Y. Lin and A. Abur, “A new framework for detection and identification of network parameter errors,” IEEE Transactions on Smart Grid, vol. 9, no. 3, pp. 1698-1706, May 2018.
  • Y. Lin and A. Abur, “Fast correction of network parameter errors,” IEEE Transactions on Power Systems, vol. 33, no. 1, pp. 1095-1096, Jan 2018.
  • Y. Lin and A. Abur, “Enhancing network parameter error detection and correction via multiple measurement scans,” IEEE Transactions on Power Systems, vol. 32, no. 3, pp. 2417-2425, May 2017.
  • Y. Lin and A. Abur, “Highly efficient implementation for parameter error identification method exploiting sparsity,” IEEE Transactions on Power Systems, vol.32, no.1, pp. 734-742, Jan 2017.
  • Y. Lin, L. Shi, L. Yao, Y. Ni, S. Qin, R. Wang, and J. Zhang, “An analytical solution for voltage stability mechanism incorporating wind power,” Journal of Electrical Engineering and Technologies, vol. 10, no. 3, pp. 865-876, May 2015.
  • Y. Lin, L. Shi, L. Yao, Y. Ni, and B. Masoud, “A multi-criteria integrated method for voltage vulnerability assessment,” Automation of Electric Power Systems, vol. 28, no. 23, pp. 54-59, Dec 2014.

Conference Publications

  • M. Z. Islam, Y. Lin*, V. M. Vokkarane, Y. Yao, and F. Ding, “Cyber-physical reconfiguration for disaster resilience of power distribution systems,” IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm), Glasgow, UK, 2023. (accepted)
  • Z. Li, Z. Shi, J. Zhao, G. Ruan, and Y. Lin, “Resilience oriented operation of power distribution networks with line hardening and comprehensive reconfiguration measures,” IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm), Glasgow, UK, 2023. (accepted)
  • A. Kumar, Y. Lin*, H. Huang, X. Lu, and Y. Zhao, “Dynamic-state-estimation-based cyber attack detection for inverter-based resources,” IEEE Power & Energy Society General Meeting (PESGM), Orlando, Florida, USA, 2023. (accepted)
  • A. Kumar, Y. Lin*, and X. Lu, “Identification of power islands via event-triggered decaying current injection by inverter networks,” IEEE Power & Energy Society General Meeting (PESGM), Orlando, Florida, USA, 2023. (accepted)
  • S. N. Edib, Y. Lin, V. M. Vokkarane, “Disaster-resilient PMU network design,” IEEE International Conference on Communication (ICC), Rome, Italy, 2023. (accepted)
  • M. Z. Islam, V. M. Vokkarane, Y. Lin, “”PMU network routing for resilient observability of power grids,” IEEE International Conference on Communication (ICC), Rome, Italy, 2023. (accepted)
  • E. Meriaux, D. Koehler, M. Z. Islam, V. M. Vokkarane, and Y. Lin, “Performance comparison of machine learning methods in DDoS attack detection in smart grids,” IEEE MIT Undergraduate Research Technology Conference (URTC), Cambridge, Massachusetts, USA, 2022.
  • S. N. Edib, Y. Lin*, V. M. Vokkarane, F. Qiu, R. Yao, and D. Zhao, “PMU and communication infrastructure restoration for post-attack observability recovery of power grids,” IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm), Phoenix, Arizona, USA, 2020.
  • B. Xie, D. Zhao, T. Hong, A.Q. Huang, Z. Guo, and Y. Lin, “Dynamic state estimation based monitoring of high frequency transformer,” IEEE International Conference on Communications, Control, and Computing Technologies for Smart Grids (SmartGridComm), Phoenix, Arizona, USA, 2020.
  • L. Ding, Y. Men, Y. Du, X. Lu, B. Chen, and Y. Lin, “Region-based stability analysis of resilient distribution systems with hybrid grid-forming (gfm) and grid-following (gfl) inverters,” IEEE Energy Conversion Congress and Expo (ECCE), Detroit, Michigan, USA, 2020.
  • Y. Jia, Y. Liu, Y. Lin, and B. Wang, “Improved dynamic state estimation based protection on VSC-HVDC transmission lines with full exploitation of information redundancy,” IEEE Power & Energy Society General Meeting, Montreal, Canada, 2020.
  • Z. Zhen, Z. Xuan, F. Wang, and Y. Lin, “Surface irradiance distribution mapping model for photovoltaic power station based on ground-based sky images,” Industrial & Commercial Power Systems (I&CPS) Technical Conference, Las Vegas, CA, USA, 2020.
  • F. Wang, Z. Zhang, H. Chai, Y. Yu, T. Wang, and Y. Lin, “Deep learning based irradiance mapping model for solar PV power forecasting using sky image,” IEEE Industry Applications Society Annual Meeting, Baltimore, MD, USA, 2019.
  • Y. Lin, A. Abur, and H. Xu, “Critical model parameters: a security vulnerability in electricity market operation,” IEEE Powertech, Milan, Italy, 2019.
  • Y. Lin and A. Abur, “Identifying security vulnerabilities of weakly detectable network parameter errors in congestion revenue right markets”, Allerton Conference on Communication, Control and Computing, University of Illinois at Urbana-Champaign, IL, USA, 2017.
  • Y. Lin and A. Abur, “Efficient identification of multiple bad data”, North American Power Symposium, Morgantown, WV, USA, 2017.
  • Y. Lin and A. Abur, “Robust transformer tap estimation,” IEEE Powertech, Manchester, UK, 2017.
  • Y. Lin and A. Abur, “Strategic use of PMUs to improve network parameter error detection,” North American Power Sym¬posium, Denver, CO, USA, 2016.
  • Y. Lin and A. Abur, “Improving network parameter error detection via multiple measurement scans,” Innovative Smart Grid Technologies, Minneapolis, MN, USA, 2016.
  • Y. Lin and A. Abur, “A computationally efficient method for identifying network parameter errors,” Innovative Smart Grid Technologies, Minneapolis, MN, USA, 2016.
  • H. Chen, L. Shi, Y. Lin, L. Yao, B. Yang, and Y. Li, “A solution of static voltage stability assessment based on pq plane analysis incorporating load uncertainty,” IEEE TENCON Region 10 Conference, Macao, China, 2015.
  • Y. Lin and A. Abur, “Efficient computation of covariance matrix entries,” North American Power Symposium, Charlotte, NC, USA, 2015.
  • Y. Lin and S. Lei, “Comprehensive probability analysis on voltage stability of power grid with wind farm connected,” The IEEE International Workshop on Intelligent Energy Systems, Vienna, Austria, 2013.
  • Y. Lin, L. Shi, Z. Jian, L. Yao, X. Lin, and B. Masoud, “A multi-criteria integrated probabilistic voltage vulnerability assessment method,” IEEE Power & Energy Society General Meeting, Vancouver, Canada, 2013.
  • X. Lin, N. Cao, and Y. Lin, “Optimal control for a class of nonlinear systems with state delay based on Adaptive Dynamic Programming with ε-error bound,” IEEE Symposium on Adaptive Dynamic Programming And Reinforcement Learning, Sin¬gapore, 2013.
  • X. Lin, Y. Huang, N. Cao, and Y. Lin, “Optimal control scheme for nonlinear systems with saturating actuator using ε-itera¬tive adaptive dynamic programming,” UAKCC International Conference on Control, Cardiff, UK, 2012.
  • Y. Lin, L. Shi, Y. Ni, L. Yao, and B. Masoud, “Multi-criteria voltage vulnerability index based on data envelopment analysis,” IET International Conference on Advances in Power system Control, Operation and Management, Hong Kong, China, 2012.
  • Y. Lin, “Excitation control system based on multi-objective heuristic dynamic programming,” IEEE Power Engineering and Automation Conference, Wuhan, China, 2011.
  • Y. Lin and C. Lu, “Application of dual heuristic programming in excitation system of synchronous generators,” International Symposium on Neural Networks, Guilin, China, 2011

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