A Wide-Area System for Power Transmission Security Enhancement Using a Process Systems Approach

Lead Research Organisation: Imperial College London
Department Name: Chemical Engineering

Abstract

Following a series of serious power blackout incidents in 2003, policy makers in the European Union and the USA have highlighted (i) the need for improved a.c. transmission grid infrastructure and advanced control technologies to enhance stability and security in an increasingly complex operating environment, and (ii) the importance of emerging measurement-based technology towards achieving such enhanced operation. The concept of this proposal is a system for transmission security assessment using the emerging measurement technologies of high-bandwidth SCADA systems and the wide area measurement systems (WAMS) which are based on time-synchronized phasor measurement units. It will lead to better situational awareness and initiate control action for optimal operation closer to loading constraints while reducing the risks of blackouts.Very recent developments in measurement-based analyses being used in oil, gas and chemicals plants point the way towards much better signal analysis applications for the emerging measurement-based technologies in power transmission systems. The measurement-based system proposed in this project would greatly extend the basic methods that are used at present and will lead to localization and real-time diagnosis of the root causes of threats to transmission system security and actions to control the situation. It offers a more predictive, responsive and accurate approach than the transmission system models which are currently used, while the signal analysis methods now being used in experimental WAMS and high-bandwidth SCADA systems would advance from their current narrow emphasis on Fourier methods adopted from the aerospace industries. For instance the project would develop signal analysis methods for use when transient events excite system non-linearities. This will provide a much more accurate indication of the true situation during developing emergencies.This project is timely and is giving an immediate response to research needs identified in the Spring of 2006 in policy documents from the EU and US. Success in shifting the emphasis from model-based to measurement-based assessments will benefit the wider field of a.c. transmission stability and security as well as creating an a.c. transmission security enhancement system in a fit state for technology transfer. A first-rate team has been assembled for the task, namely Imperial College London (expertise in robust damping control of inter-area oscillations) and UCL (expertise in measurement-based analysis for process systems), National Grid (provision of high-bandwidth SCADA data, system specification and testing, a UK industrial viewpoint) and ABB (provision of PMU data, system development, the industrial viewpoint from continental Europe). The university researchers will do part of the work on secondment with National Grid and ABB. It is quite realistic to expect success from this team.
 
Description The research conducted in EP/E03232X/1 has addressed the enhancement of grid stability and security in a.c. power transmission systems. In this context, grid security means uninterrupted power transmission. The work is of significance because of challenges posed by renewable generation from new wind farms and projected changes in the grid infrastructure in the UK. The idea was to use the emerging measurement technology of wide area measurement systems (WAMS) based on time-synchronized phasor measurement units (PMUs). The study used methods for near real-time analysis. It included multivariate methods whereby time trends of the measurements from different locations were analysed together to give information about the geographical distribution of emerging stability problems as well as their evolution over time.

The outcome was a method for early detection of a type of instability called a wide-area oscillation using WAMS data from ambient operation (i.e. during everyday routine operation). It finds the frequency and damping ratio of the oscillation. If the damping becomes too small then grid operators have to take action, hence early warning is of benefit. The PhD student engineered a software tool and interface which displays the time evolution of damping and frequency of the oscillating mode, and locates where in the grid the mode is most strongly present. The project adapted methods of multivariate signal analysis from the process sector (oil, gas and chemicals) where measurement-based analysis has been long established. Methods from structural engineering for detecting vibrations in buildings were also useful.

Estimation of system damping during ambient operation is a significant advance. Previously, damping and mode frequency have had to wait for the onset of a system fault or event which would initiate a clear transient oscillatory response called a ring-down. The problem with waiting for ring-downs is that they are rare and may only occur after a grid problem has already arisen. Alternatively, oscillation frequency and damping have been estimated off-line from models, however models are becoming less accurate because of uncertainties in renewable generation now linked to the grid.
Exploitation Route The results of the project have been disseminated via four journal publications, a PhD thesis and in further papers published in the related grant of Dr B.C. Pal (EP/E032435/1) in EE Engineering at Imperial. Co-authors include Dr Pal and the postdoctoral researcher supported by EP/E032435/1. An international workshop was held at Imperial in April 2010 organized by Dr Pal. A report of the workshop is at: http://www3.imperial.ac.uk/processautomation/news.

New collaborations have developed. Aalto University in Finland and Fingrid, the Finnish grid transmission operator, have joined Imperial, National Grid and ABB to publish a study of the performance of the developed method using data from the Finnish part of the Scandinavian grid and also from simulation (where the damping was known). Further contacts include Statnett in Norway who operate the Norwegian part of the Scandinavian transmission grid. The expanded group made a successful bid for an FP7 project which is coordinated by Imperial College London (Thornhill and Pal). The project is a EUR1.1M FP7 Marie Curie project which started in September 2010. The partners are Aalto University, ABB, Fingrid, GE Research, National Grid, Imperial, Statnett and the Technical University of Graz. The new project concerns monitoring and management of high voltage transmission grids. The investigators thank EPSRC for funding project EP/E03232X/1 which made possible all the above activity.
Sectors Energy
URL http://www.imperial.ac.uk/process-automation/research/wams/wams/
 
Description The outcome was a method for early detection of a type of instability called a wide-area oscillation using WAMS data from ambient operation (i.e. during everyday routine operation). It finds the frequency and damping ratio of the oscillation. If the damping becomes too small then grid operators have to take action, hence early warning is of benefit. The PhD student engineered a software tool and interface which displays the time evolution of damping and frequency of the oscillating mode, and locates where in the grid the mode is most strongly present. The project adapted methods of multivariate signal analysis from the process sector (oil, gas and chemicals) where measurement-based analysis has been long established. Methods from structural engineering for detecting vibrations in buildings were also useful.
First Year Of Impact 2011
Sector Energy
Impact Types Economic
 
Description REAL-SMART: Using real-time measurements for monitoring and management of power transmission dynamics for the Smart Grid
Amount € 900,000 (EUR)
Funding ID PIAP-GA-2009-251304-REAL-SMART 
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 09/2010 
End 08/2014
 
Description ABB Ltd 
Organisation ABB Group
Country Switzerland 
Sector Private 
Start Year 2007
 
Description National Grid 
Organisation National Grid UK
Country United Kingdom 
Sector Private 
Start Year 2007