Faculty Publications
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Item An integrated PMU architecture for power system applications(De Gruyter Open Ltd, 2022) Aalam, M.K.; Shubhanga, K.N.Time synchronized phasors obtained using Phasor Measurement Units (PMU) spread across wide areas have revolutionized power system monitoring and control. These synchronized measurements must be accurate and fast in order to comply with the latest IEEE standards for synchrophasor measurements. The speed at which a PMU provides an output depends on the group delay associated with that PMU and the permissible group delay in-turn decides the utility of a PMU for either control or measurement application. Based on the group delay compensation techniques, in the literature, two individual types of PMUs, such as causal and non-causal PMUs have been introduced. This paper presents an approach where both causal and non-causal PMUs are combined in an integrated PMU architecture. This method not only illustrates the group delay performance of two PMUs in a single module, but also can be used for multiple functions. In this environment several PMU algorithms have been compared with respect to their group delays and their effect on the response time. Application of the integrated PMU architecture to a four-machine 10-bus power system has been demonstrated using a six-input PMU with three-phase voltage and current signals as inputs. Different causal compensation schemes are introduced due to the availability of voltage and current-based frequency and ROCOF signals. Impact of these compensation schemes on PMU accuracy is evaluated through the Total Vector Error (TVE) index. The influence of these compensation schemes on measurements like power and impedance is also investigated. Finally, outputs from the integrated PMU architecture are fed into a Power System Stabilizer (PSS) to control the small-signal stability performance of a power system during dynamic conditions. © 2021 Walter de Gruyter GmbH, Berlin/Boston.Item Frequency estimation using signal reconstruction approach(Elsevier Ltd, 2024) Aalam, M.K.; Shubhanga, K.N.Frequency estimated throughout the wide-spread grid is used for monitoring and controlling various local as well as global power system phenomena. Such applications require precise frequency estimation, especially during challenging power system conditions when signals are non-stationary or contain harmonics. Therefore, in this paper, a signal-reconstruction-based approach has been described to estimate the frequency and rate-of-change of frequency (ROCOF) for a single-phase system. The approach is based on the idea that the frequency information in case of a reconstructed signal is preserved even during off-nominal frequency conditions. Single-phase reconstructed time-domain signals are proposed as an alternative to phase-angle signals for frequency estimation. From the reconstructed time-domain signals, the frequency is estimated using the convolution average filter (CAF) based method and a single-phase demodulation technique employing Hilbert filter (HFD). The effectiveness of this approach especially during off-nominal and inter-harmonic conditions is demonstrated using the synchrophasor standard based test signals. The proposed method is compared against state-of the art single-phase phasor measurement unit based estimates. Accuracy of the reconstruction-based approach is also verified through signals obtained from the ISO-New England power system and simulation based studies. The output frequency and ROCOF signals are also used for mode identification using the Prony method. © 2023 Elsevier B.V.