%0 Journal Article
%J IEEE Transactions on Power Systems
%D 2015
%T Fast SVD Computations for Synchrophasor Algorithms
%A Wu, Tianying
%A S. Arash Nezam Sarmadi
%A Venkatasubramanian, Vaithianathan
%A Pothen, Alex
%A Kalyanaraman, Ananth
%K AA13-004
%X Many singular value decomposition (SVD) problems in power system computations require only a few largest singular values of a large-scale matrix for the analysis. This letter introduces two fast SVD approaches recently developed in other domains to power systems for speeding up phasor measurement unit (PMU) based online applications. The first method is a randomized SVD algorithm that accelerates computation by introducing a low-rank approximation of a given matrix through randomness. The second method is the augmented Lanczos bidiagonalization, an iterative Krylov subspace technique that computes sequences of projections of a given matrix onto low-dimensional subspaces. Both approaches are illustrated on SVD evaluation within an ambient oscillation monitoring algorithm, namely stochastic subspace identification (SSI).
%B IEEE Transactions on Power Systems
%P 1 - 2
%8 03/2015
%! IEEE Trans. Power Syst.
%R 10.1109/TPWRS.2015.2412679
%0 Journal Article
%J IEEE Transactions on Power Systems
%D 2015
%T Inter-Area Resonance in Power Systems From Forced Oscillations
%A S. Arash Nezam Sarmadi
%A Venkatasubramanian, Vaithianathan
%K AA13-004
%K AARD
%K CERTS
%K RTGRM
%X This paper discusses a recent event in the western American power system when a forced oscillation was observed at a frequency that was close to a well-known 0.38-Hz inter-area electromechanical mode frequency of the western system. The event motivates a systematic investigation in this paper on the possibility of resonant interactions between forced oscillations and electromechanical inter-area oscillatory modes in power systems. When the natural oscillatory mode of a power system is poorly damped, and the forced oscillation occurs at a frequency close to system mode frequency at critical locations for the mode, resonance is observed in simulation test cases of the paper. It is shown that the MW oscillations on tie-lines can be as high as 477 MW from a 10-MW forced oscillation in Kundur test system because of resonance. This paper discusses the underlying system conditions and effects as related to resonance in power systems caused by forced oscillations and discusses ways to detect such scenarios using synchrophasors. Simulated data from Kundur two-area test power system as well as measurement data from western American power system are used to study the effect of forced oscillations in power systems.
%B IEEE Transactions on Power Systems
%P 1 - 9
%8 02/2015
%! IEEE Trans. Power Syst.
%R 10.1109/TPWRS.2015.2400133
%0 Journal Article
%J IEEE Transactions on Power Systems
%D 2014
%T Electromechanical Mode Estimation Using Recursive Adaptive Stochastic Subspace Identification
%A S. Arash Nezam Sarmadi
%A Venkatasubramanian, Vaithianathan
%K AA13-004
%K AARD
%K CERTS
%K oscillations
%K phasor measurement units (PMUs)
%X Measurement based algorithms for estimating low-frequency electromechanical modes serve as useful practical methods to monitor the modal properties of power system oscillations in real-time. This paper proposes a recursive adaptive stochastic subspace identification (RASSI) algorithm for online monitoring of power system modes using wide-area synchrophasor data. The proposed method gives an online estimation of mode frequency and damping ratio as well as mode shapes using multi-channel measurement data. It exploits both the accuracy of subspace identification and fast computational capability of recursive methods. An adaptive method is proposed to enable fast tracking of modal evolution under poorly damped conditions together with low estimation variance under quasi-steady-state conditions. The algorithms are tested using simulated data from Kundur two-area test power system as well as measured data from real systems.
%B IEEE Transactions on Power Systems
%V 29
%P 349 - 358
%8 01/2014
%N 1
%! IEEE Trans. Power Syst.
%R 10.1109/TPWRS.2013.2281004
%0 Journal Article
%J IEEE Transactions on Power Systems
%D 2014
%T Two-Level Ambient Oscillation Modal Estimation From Synchrophasor Measurements
%A Ning, Jiawei
%A S. Arash Nezam Sarmadi
%A Venkatasubramanian, Vaithianathan
%K AA13-004
%K AARD
%K CERTS
%K oscillations
%K phasor measurement units (PMUs)
%X This paper proposes a decentralized two-level structure for real-time modal estimation of large power systems using ambient synchrophasor data. It introduces two distributed algorithms that fit the structure well, namely, 1) decentralized frequency domain decomposition and 2) decentralized recursive stochastic subspace identification. As opposed to present-day oscillation monitoring methodologies, the bulk of the algorithmic computations is done locally at the substation level in the two-level framework. Substation modal estimates are sent to the control center where they are grouped, analyzed, and combined to extract system modal properties of local and inter-area modes. The framework and the proposed algorithms provide a scalable methodology for handling oscillation monitoring from a large number of substations efficiently. The two-level structure and the two decentralized algorithms are tested using simulated data from standard test systems and from archived real power system synchrophasor data.
%B IEEE Transactions on Power Systems
%P 1 - 10
%8 12/2014
%! IEEE Trans. Power Syst.
%R 10.1109/TPWRS.2014.2373172