Football is, arguably, the most globalized sport in the world. Since the official date of its foundation, back in 1863, it has spread around the planet, reaching almost every country. Over time, ...Football roots grew so attached to society that it is a valid indicator to understand how the social order responds to general crises. In 1911 in the IFA Shield tournament when Mohun Bagan defeated the British side, East Yorkshire Regiment, and took home the shield. This was Indian football's 'Lagaan' moment. Even during the period between 1950 and 1962 is often considered to be the 'Golden Era' of Indian football, so much so that India was often referred to as the 'Brazil of Asia'. But where are we now? The latest FIFA rankings places India at the 105th position. We are a country of 1.3 billion people failing to produce a well-built set of players, who can challenge European, South American, or even our South Asian counterparts consistently. So, it certainly begs the question: Where are we going wrong?
Determination of the sources of oscillations in the power system helps operators take appropriate preventive actions. In recent years, the dissipating energy flow (DEF) method has emerged as a ...promising tool for the online localization of low-frequency oscillation sources. In literature, the mathematical foundation of the DEF method is well-studied for networks with synchronous generators. In this paper, we extend the analysis to flexible AC transmission systems (FACTS). We derive the DEF-expressions for a thyristor controlled series capacitor (TCSC) and a static synchronous compensator (STATCOM) operating with conventional control strategies. Specifically, TCSC with both fixed and variable compensation, and STATCOM in grid-following mode with dc-link voltage and ac voltage-reactive power droop control are considered. Analyzing their respective DEFs, we obtain the conditions for which these FACTS devices could appear as the sources of low-frequency oscillations. Our findings are structured into propositions and are supported through numerical case studies on IEEE test systems.
In bulk power systems, detecting the sources of low-frequency oscillations can be challenging. The energy-based approaches for oscillation source localization are known to have better accuracy ...compared to others. The dissipating energy flow (DEF) method is one such approach with notable success in localizing real-world oscillation cases. While the mathematical justifications for the method's characterization of a device as an oscillation source (or sink) is well-exposed for synchronous generators and standalone inverters, no insights have been developed for power-electronics-interfaced dc transmission systems. To fill this gap, this paper presents a theoretical analysis of the DEF in a voltage source converter-based high voltage direct current (VSC-HVdc) system. Passivity-based analysis is performed to explain why a VSC-HVdc system, operating at unity power factor, with the commonly used control strategy involving constant real power control, dc-link voltage control, and ac voltage-reactive power droop control is a source of oscillation energy. Supporting case studies are performed on the IEEE 4-machine and IEEE 16-machine 68- bus test systems.
This paper proposes an improvement on the standalone robust principal component analysis (R-PCA)-based approach for recovering clean signals from corrupted synchrophasor measurements. The ...contributions of this paper are twofold. First, a kernel principal component analysis (K-PCA)-based metric is proposed for detecting and differentiating event-induced outliers from spurious outliers in data, which is then used as an indicator to suspend R-PCA in the event window to minimize the overall error in signal recovery. Second, a formal approach based on the recursive Bayesian framework is proposed for selecting the most appropriate subspace from a library of subspaces to be used by R-PCA. The paper combines the ideas of robust signal recovery, corruption-resilient event outlier detection, and stochastic subspace selection into a composite approach for correcting anomalies in synchrophasor data. The effectiveness of the proposed methodology is validated on simulated data from IEEE 16-machine, 5-area test system.
Insights are developed into grouping PMU signals for guaranteeing data recovery under sparse corruption. Analytical relations are derived to express the denseness of the subspace spanned by a ...measurement window in terms of the modal observabilities of its constituent signals. It is shown that grouping signals by minimizing variation in phase angles and amplitudes of observabilities for each poorly-damped mode minimizes the numerical-rank of the measurement window, enhances denseness of the subspace, and helps in attaining the sufficiency condition guaranteeing exact recovery using Robust Principal Component Analysis-based signal reconstruction methods. These insights are structured into lemmas and propositions for signal selection and are validated on synthetic data from IEEE test systems, as well as field PMU data from a US utility.
Clustering is one of the most vital image segmentation techniques. However, proper image clustering has always been a challenging task due to blurred and vague areas near to concerned object ...boundaries. Therefore, rough set based clustering techniques like Rough k-means (RKM) has been employed in image clustering domain because rough set concept can handle the overlapping clusters to a great extent. RKM shows the performance in image clustering domain as a similarity based clustering model like K-Means and Fuzzy C-Means. Therefore, this paper presents an up-to-date review on rough set based image clustering approaches with their merits and demerits. The measures of similarity as well as the evaluation criteria for rough clustering are also discussed in this study. Beside that the key issues which are involved during the development of rough set based clustering models are investigated in this paper.
This letter establishes a relationship between the concepts of damping torque and the dissipation of transient energy in a multimachine power system with constant power loads. To that end, we present ...a mathematical proof showing that, for a poorly-damped mode, the total damping power stemming from the interaction of electromagnetic torques and rotor speeds is approximately equal to the average rate of transient energy dissipation in the system corresponding to the modal oscillation. This is verified with numerical studies on the IEEE 2-area 4-machine and 5-area 16-machine test systems.
Determination of the sources of oscillations in the power system helps operators take appropriate preventive actions. In recent years, the dissipating energy flow (DEF) method has emerged as a ...promising tool for the online localization of low-frequency oscillation sources. In literature, the mathematical foundation of the DEF method is well-studied for networks with synchronous generators. In this paper, we extend the analysis to flexible AC transmission systems (FACTS). We derive the DEF-expressions for a thyristor controlled series capacitor (TCSC) and a static synchronous compensator (STATCOM) operating with conventional control strategies. Specifically, TCSC with both fixed and variable compensation, and STATCOM in grid-following mode with dc-link voltage and ac voltage-reactive power droop control are considered. Analyzing their respective DEFs, we obtain the conditions for which these FACTS devices could appear as the sources of low-frequency oscillations. Our findings are structured into propositions and are supported through numerical case studies on IEEE test systems.
Bad data outliers and malicious corruption in Phasor Measurement Unit (PMU) data having signature similar to that of a highly nonlinear event-induced oulier can challenge reliable event detection ...when linear principal component analysis (PCA)-based metrics are used. This paper presents a moving window based kernel PCA approach for accurately detecting event-induced outliers in presence of such corruptions in data. It is demonstrated that with appropriate tuning of kernel parameters, the change in the square of the norm of principal component score between successive windows along the direction of maximum variance in feature space can be used as a metric for corruption-resilient detection of event-induced outliers. Analytical justification for the same is provided along with a bound on this change. The performance of the proposed metric is validated on both synthetic data and field measurements.
This paper proposes an improvement on the standalone robust principal component analysis (R-PCA)-based approach for recovering clean signals from corrupted synchrophasor measurements. The ...contributions of this paper are twofold. First, a kernel principal component analysis (K-PCA)-based metric is proposed for detecting and differentiating event-induced outliers from spurious outliers in data, which is then used as an indicator to suspend R-PCA in the event window to minimize the overall error in signal recovery. Second, a formal approach based on the recursive Bayesian framework is proposed for selecting the most appropriate subspace from a library of subspaces to be used by R-PCA. The paper combines the ideas of robust signal recovery, corruption-resilient event outlier detection, and stochastic subspace selection into a composite approach for correcting anomalies in synchrophasor data. The effectiveness of the proposed methodology is validated on simulated data from IEEE 16-machine, 5-area test system.
