Research Focus: Major Contributions
High Voltage DC (HVDC) transmission & Multi-terminal DC (MTDC) systems (Funded by NSF CAREER Award ECCS1656983):
We have proposed a ratio-based frequency support mechanism from MTDC grids to the ac grids, which can help in solving the critical issue of progressively reducing inertia in grids due to the retirement of conventional generators. To this end, analytical constraints on droop coefficients were established to achieve these ratios. Most importantly, we have established for the first time, an analytical stability boundary in frequency droop controller parameter space for MTDC grids. Please see –
Cascading failure in energy CPS (Funded by NSF CPS Medium Grant — ECCS1836827):
The ground truth for cascading failure in power system can only be obtained through a detailed dynamic model involving nonlinear differential and algebraic equations whose solution process is computationally expensive. This has prohibited adoption of such models for cascading failure simulation. To solve this, we have proposed a fast cascading failure simulation approach, which lends itself to statistical analysis. The proposed approach achieved on average a 35x speedup compared to traditional methods in a 2,383-bus Polish network. This presumably is a big leap forward in overcoming a major hurdle in power systems domain. A provisional US patent has been filed by Penn State on this concept. The details can be found in https://www.sciencedirect.com/science/article/pii/S0306261922017913
Cyber security of PMU data in wide-area monitoring (Funded by NSF CPS Small Grant — CNS1739206):
Monitoring low-frequency oscillations using phasor measurement units (PMUs) is important in ensuring stability and security of large power networks. In this context, we ask the following research question − can we intelligently locate the PMUs and/or group signals from installed PMUs such that the resulting combinations guarantee data recovery from corruption while capturing every information necessary to estimate the critical modes. We show that the denseness of a subspace derived from a measurement window can be bounded by denseness of the observability submatrix obtained from the small-signal model corresponding to the poorly-damped modes in the system under a weak assumption. See https://ieeexplore.ieee.org/abstract/document/9089353
Power systems dynamics, stability, and controls (Funded by NSF CPS Small Grant — CNS1739206):
Damping torque analysis, as introduced by Park in his 1933 paper and furthered by Concordia, Shepherd, and notable others, helps develop insightful understanding of the stabilizing contributions coming from a synchronous machine and its governor and excitation systems. Complementary to this, the Lie derivative of a Lyapunov-like transient energy function is another control theoretic measure of system’s damping. Although some of the initial works highlighted an intuitive link between damping torque and dissipation of transient energy (and indirectly with the passivity theory), it is only in the recent works that a rigorous mathematical connection between the two has been established for a single-machine-infinite-bus system. We have made the maiden successful attempt to establish such a connection for multimachine systems. This is important given the critical emphasis attributed to the theory of damping torque in power system stability analysis, as is evident from classical textbooks. Please see https://ieeexplore.ieee.org/abstract/document/9580483
System Integration of Grid-forming & Grid-following Converters (Funded by US Department of Energy and NSF):
We are involved in fundamental research on grids under transition that have synchronous machines, grid-following converters, and grid-forming converters. Please see the following works that perform nonlinear stability analysis and apply nonlinear control theory
Smart Grid
Facilities
RTDS NOVACOR integrated with SEL 487E PMU, SEL 3350 RTAC, SEL GPS Clock, and Opal-RT OP4510 Real-Time Simulator
