Faculty Publications
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Item MAPE-An Alternative Fitness Metric for Prony Analysis of Power System Signals(De Gruyter peter.golla@degruyter.com, 2018) Rao, K.; Shubhanga, K.N.Phasor Measurement Units have facilitated tracking of oscillations in power system response signals. This has provided an impetus for identifying unstable component modes directly from oscillatory signals. Prony analysis, the earliest method proposed for this purpose, throws up some trivial modes. These not only distract the analyzer but also prolong processing time thereby delaying corrective action. Hence the fitness metric chosen should serve to minimize the number of trivial modes. The conventional fitness metric is Signal-To-Noise Ratio (SNR), which is actually Signal-To-Estimation error Ratio (SER). This paper proposes that Mean Absolute Percentage Error (MAPE) can also serve well as a fitness metric. It is shown through case studies carried out on well-known four-machine power system that there are a few cases where MAPE performs better than SER while in some instances SER works better. This inference is verified even in the presence of measurement noise. Hence a novel fitness metric is proposed combining MAPE with SER. Case studies on simulated signals obtained from New England-power system prove that this novel metric can achieve considerable reduction in processing time. Besides, an exponential binary search has been suggested for determining the optimal model order in minimum number of iterations. © 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.Item Voltage estimation of active distribution network using PMU technology(Institute of Electrical and Electronics Engineers Inc., 2021) Tangi, S.; Gaonkar, D.N.As the Distributed Generation (DG) is evolving, the distribution network has undergone tremendous change. The DG sources like wind and solar are intermittent in nature. Hence to estimate the Active distribution network's (ADN) parameters (Voltage and Current) accurately with the DG variation, the traditional offline method like long-term smart distribution network planning (with off-line variant) method is not feasible in terms of network's reliability and operation. In this work, an online voltage estimation technique using PMU (Phasor Measurement Unit) technology is proposed to enhance a distribution network's reliable operation and real-time monitoring. The proposed estimation method does not require PMU units at all nodes in the network. The estimation of unknown states information can be achieved from available PMU unit's data. The proposed methodology is economical and feasible for voltage estimation, and system observability as the number of PMU units required is less. The standard IEEE Distribution network systems are considered for checking the feasibility of the recommended technique. For the simulation of the case studies, MATLAB programming is used. A Forward and Backward sweep (FBS) load-flow algorithm is used to authenticate the proposed methodology. © 2013 IEEE.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 Security-constrained optimal placement of PMUs using Crow Search Algorithm(Elsevier Ltd, 2022) Johnson, T.; Moger, T.For precise power system monitoring, a major focus is on involvement of the latest technology based on phasor measurement units (PMUs). As the sole system monitor, state estimator plays an important role in the security of power system operations. Optimal placement of PMUs (OPP) with numerical observability ensures reliable state estimation. For economical and efficient utilization, there is a need to optimize the placement of PMUs in the power system network. A new approach called Crow Search Algorithm (CSA) devised by others, has been used to solve an OPP problem. The performance of this new approach is compared to the dominant method for an optimization problem — binary integer linear programming (BILP). Comparison studies have also been carried out with particle swarm optimization (PSO) method. The major constraints such as topological, numerical observability conditions with and without zero-injection buses (ZIBs) are considered. Contingencies and limitation of measurement channels in a PMU device are also incorporated as constraints. The main advantage of using the CSA is that it provides multiple location sets for same optimal number of PMUs (optimal number same as obtained by BILP). While BILP method provides only one set of locations for the optimal number of PMUs obtained. This becomes advantageous in planning stage for power engineers for placing PMUs. Test systems considered for the case studies are of varied sizes such as IEEE 14-bus, IEEE 30-bus, IEEE 57-bus and 72-bus practical equivalent system of Indian southern region power grid. © 2022 Elsevier B.V.Item Power system event detection and localization—A new approach(Elsevier Ltd, 2023) Aalam, M.K.; Shubhanga, K.N.Time-synchronized estimates acquired using the Wide Area Measurement System (WAMS) have substantially helped enhance the health of the modern power grid. WAMS data when used in conjunction with appropriate tools can aid in the timely detection of power system events. With the continuous expansion of the WAMS network, identification of events and narrowing down on their location is emerging as a serious challenge for power system operators. Therefore, in this paper an event detection and localization tool is developed which analyzes data obtained from multiple Phasor Measurement Units (PMUs) installed throughout the WAMS network in order to identify the occurrence of an event. The effectiveness of this tool is demonstrated using practical signals from the ISO-NE power system and simulation based signals obtained from a 4-machine 10-bus system. Occurrence of an event is flagged by comparing the wavelet energy and standard deviation values of a PMU signal against a threshold. An event localization algorithm based on the number of PMUs involved in the event detection stage is proposed. Based on the presented algorithm, disturbances are classified as local or wide-spread events. Finally, a method to identify a loss-of-synchronism condition using phase angle difference (PAD) signals obtained across transmission lines is also proposed. © 2023 Elsevier B.V.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.