Y10. System Theory, Modeling and Controls


Networked power electronics systems like FREEDM provide control challenges because they’re nonlinear, hybrid and multivariable. Stability issues exist from the lowest level to the highest as the control loop time scales increase from 1 millisecond to seconds and the corresponding instability oscillation frequency decreases from thousands of hertz to single digits. Actively controlled power converters introduce highly nonlinear and time-varying dynamics.


FREEDM researchers developed models and algorithms to address these issues. Major achievements include a comprehensive mathematical model of the FREEDM system that was incorporated into the Large Scale System Simulation testbed, defining feasibility bounds through physical and switching parameters’ analytical relationships, implementing robustness into the control design and developing a predictive current-control method for local controllers verified with passivity-based stability analysis.


In year 10, FREEDM finalized nonlinear distributed control methods for intelligent power and energy management in a feasible system domain and further developed power-sharing methods and nonlinear power-management controllers for SST-based distribution systems.


  1. T. A. Khan, A.A. Milani, A. Chakrabortty, I. Husain, “Dynamic Modeling and Feasibility Analysis of a Solid-State Transformer-Based Power Distribution System,” IEEE Transactions on Industry Applications, Volume: 54, Issue: 1, Pages: 551 – 562, Year: 2018.
  2. N. Rahbari-Asr, Y. Zhang, and M.-Y. Chow, “Consensus-based distributed scheduling for cooperative operation of distributed energy resources and storage devices in smart grids,” IET Generation, Transmission & Distribution, vol. 10, no. 5, pp. 1268–1277, 2016.
  3. A. A. Milani, M. T. A. Khan,   A. Chakrabortty, and   I. Husain, “Equilibrium Point Analysis and Power Sharing Methods for Distribution Systems Driven by Solid-State Transformers,” IEEE Transactions on Power Systems, Volume: 33, Issue: 2, Year: 2018, Pages: 1473 – 1483.
  4. M.A. Awal, W. Yu and I. Husain, “Predictive Current Control for Stabilizing Power Electronics Based AC Power Systems” IEEE Energy Conversion Congress & Expo (ECCE2017), Cincinnati, OH, Oct. 2017.
  5. Gao, X. She, I. Husain and A. Huang, “Solid-State Transformer Interfaced Permanent Magnet Wind Turbine Distributed Generation System with Power Management Functions,” IEEE Transactions on Industry Applications. Year: 2017, Volume: 53, Issue: 4, Pages: 3849 – 3861.
  6. S. Falcones, R. Ayyanar, and X. Mao, “A DC–DC Multiport-Converter-Based Solid-State Transformer Integrating Distributed Generation and Storage, IEEE Transactions on Power Electronics, Year: 2013, Volume: 28, Issue: 5, Pages: 2192 – 2203 (150 Citations)
  7. T. Yao, I. Leonard, R. Ayyanar, K. Tsakalis, “Mu synthesized robust controller for multi-SST islanded smart grid,” 2016 IEEE Energy Conversion Congress and Exposition (ECCE), 2016.