Worcester Polytechnic Institute Electronic Theses and Dissertations Collection

Title page for ETD etd-050107-124815

Document Typedissertation
Author NamePajic, Slobodan
Email Address slobodan.pajic at gmail.com
TitlePower System State Estimation and Contingency Constrained Optimal Power Flow - A Numerically Robust Implementation
DepartmentElectrical & Computer Engineering
  • Dr. Kevin A. Clements, Advisor
  • Dr. Paul W. Davis, Committee Member
  • Dr. Marija Ilic, Committee Member
  • Dr. Homer F. Walker, Committee Member
  • Dr. Alexander E. Emanuel, Committee Member
  • Keywords
  • Importance Sampling
  • CGNR
  • LSQR
  • Contingency Constrained OPF
  • Trust-region methods
  • State Estimation
  • Date of Presentation/Defense2007-04-20
    Availability unrestricted


    The research conducted in this dissertation is divided into two main parts. The first part provides further improvements in power system state estimation and the second part implements Contingency Constrained Optimal Power Flow (CCOPF) in a stochastic multiple contingency framework.

    As a real-time application in modern power systems, the existing Newton-QR state estimation algorithms are too slow and too fragile numerically. This dissertation presents a new and more robust method that is based on trust region techniques. A faster method was found among the class of Krylov subspace iterative methods, a robust implementation of the conjugate gradient method, called the LSQR method.

    Both algorithms have been tested against the widely used Newton-QR state estimator on the standard IEEE test networks. The trust region method-based state estimator was found to be very reliable under severe conditions (bad data, topological and parameter errors). This enhanced reliability justifies the additional time and computational effort required for its execution. The numerical simulations indicate that the iterative Newton-LSQR method is competitive in robustness with classical direct Newton-QR. The gain in computational efficiency has not come at the cost of solution reliability.

    The second part of the dissertation combines Sequential Quadratic Programming (SQP)-based CCOPF with Monte Carlo importance sampling to estimate the operating cost of multiple contingencies. We also developed an LP-based formulation for the CCOPF that can efficiently calculate Locational Marginal Prices (LMPs) under multiple contingencies. Based on Monte Carlo importance sampling idea, the proposed algorithm can stochastically assess the impact of multiple contingencies on LMP-congestion prices.

  • PhD_dissertation.pdf

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