Online coherency identification and stability condition for large interconnected power systems using an unsupervised data mining technique

Identification of coherent generators and the determination of the stability system condition in large interconnected power system is one of the key steps to carry out different control system strategies to avoid a partial or complete blackout of a power system. However, the oscillatory trends, the larger amount data available and the non-linear dynamic behaviour of the frequency measurements often mislead the appropriate knowledge of the actual coherent groups, making wide-area coherency monitoring a challenging task. This paper presents a novel online unsupervised data mining technique to identify coherent groups, to detect the power system disturbance event and determine status stability condition of the system. The innovative part of the proposed approach resides on combining traditional plain algorithms such as singular value decomposition (SVD) and K -means for clustering together with new concept based on clustering slopes. The proposed combination provides an added value to other applications relying on similar algorithms available in the literature. To validate the effectiveness of the proposed method, two case studies are presented, where data is extracted from the large and comprehensive initial dynamic model of ENTSO-E and the results compared to other alternative methods available in the literature

Data analytic tool for clustering identification based on dimensionality reduction of frequency measurements

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This work presents a data analytic tool for clustering analysis based on Dimensionality Reduction (DR) of power system measurements. The proposed method is applied to frequency measurements of the ENTSO-E dynamic model of continental Europe and the results are compared with other conventional DR approaches. After considerable reduction of the raw measurements, a phasor metric for identification of coherency groups of generators is proposed. The recommended measure stands for its simple implementation, interpretation and fast computation. To illustrate the effectiveness of the clustering approach and the coherency of the metrics, a particular study case following the outage of a representative generation unit in France is presented

Power System Restoration with Black-Start Pump Storage Power Plants

One of the main duties of a transmission system operator (TSO) is to be prepared for the power system worst case, which means to restore the power system operation after a total blackout. To this aim two main principles are currently available. The first one is based on power system restoration with external voltage support and the second more challenging one is based on own voltage support from black-start generation units. The current paper describes experiences of power system restoration based on detailed dynamic system modelling and tested in the real system by interconnecting for the first time two hydro-power generation centers over the Alps and also by using as load the currently worldwide largest voltage source full converter-driven-pump of 100 MVA

Monitoring and control of power system oscillations using HVDC/FACTS and wide-area phasor measurements

Power oscillations are a growing concern among power system operators worldwide. Traditionally, the main countermeasure against dangerous power oscillations has been the installation of power system stabilizers (PSS). Essentially, the potential for inter-area power oscillations depends on the strength of the tie lines between different areas and the load on the ties. From a European perspective, with the anticipated integration of remote renewable energy sources such as offshore wind power from the North-sea region and solar power from southern Europe or Africa, we can expect the average transmission distances to grow and consequently also tie line flows. Unless tie lines are also reinforced we expect more oscillation events in the European grid in the future. From an operational point of view, it is of high priority to be able to estimate the damping of oscillatory modes reliably in real-time in order to take appropriate and timely measures in case damping becomes poor. Recent developments in wide-area phasor monitoring have resulted in a new power oscillation monitoring algorithm that uses multiple measurements from different locations in the grid. An equivalent system model of the power grid is estimated in real-time and based on this model, the damping and frequency as well the activity of oscillatory modes can be determined from ambient process variations. As basis for this, a wide-area measurement system (WAMS) can provide time synchronized signals from phasor measurement units (PMUs) that can measure voltage, current and frequency with adequate accuracy and resolution in time. This paper shows results from pilot operation of the new application at swissgrid, including recordings from an actual and representative event in the continental ENTSO-E interconnected power system. This example demonstrates the performance of the new application as well as provides information about the oscillatory modes present in the continental ENTSO-E system today. Furthermore, FACTS and HVDC systems can serve as powerful actuators to control inter-area oscillations, provided they are equipped with appropriate controller extensions. Particularly for the control and management of inter-area oscillations, remote measurements have proven useful. The paper outlines the technical aspects and suggests a design procedure for controller extensions based on local or remote measurement for the purpose of inter-area oscillation damping

Frequenzmessung beim Lastabwurf

Der automatische Lastabwurf ist eine der letzten Mass­nahmen des System­schutzes in Stromnetzen, die das Gesamt­system vor einem totalen Netz­zusammen­bruch retten kann. Entsprechend wichtig ist es bei diesem System, weder von Unter- noch von Über­funktionen «überrascht» zu werden. Studien­ergebnisse einer FNN-Arbeits­gruppe werden hier präsentiert

Influence of network constraints and product split on the possible revenue of distributed generators providing ancillary services

The total required ancillary services power will increase due to the decrease of the number of traditional generating units and rise of renewable energy resources (RES). New ancillary services providers will be necessary. Thus, RES could cov-er these new ancillary services needs. This study is focused on the PV system capability on 18 kV network to export an-cillary services to transmission level. Three different commercial behaviours, product splits, with different power share in energy and balancing market are defined. In order to evaluate the proposed product splits their revenue is calculated. Past energy tariffs and market prices as well as ancillary services market prices are used. Based on past data on second-ary and tertiary control powers, a scenario based on ancillary services market prices implementation is evaluated. Two options are considered: in option 1, the product split at maximum product price and product (secondary or tertiary con-trol) is chosen for each time interval based on the mean price and standard deviation; In option 2, the product split at maximum product price and product is chosen for each instant based on prices. The revenues are calculated based on optimal power flow results for several proposed product splits and product options

Application of resonance analysis to AC-DC networks

Medium to long-distance underground ac lines and both short- and long-distance HVdc are frequently integrated into network expansion plans. In conjunction with growing numbers of power-electronic converters in the grid, there is a rising risk related to the effects of harmonic currents. Resonance analysis should therefore be part of power system expansion planning. In this paper, network harmonic modeling and analysis are discussed, in particular, power transformer and power converter frequency models are proposed. Frequency scanning and resonance mode analysis are compared and discussed. The changes in resonance response due to transmission network expansion are drawn. The methods are applied to the investigation of the impact of one link reinforcement, both ac and ac solutions, as well as the impact of the power transformer disconnection. The performed analysis enables finding the resonance location at each studied case. The frequency analysis methods presented in this paper enable forseeing network frequency behavior that is valuable for both network analysis and network expansion planning