Stability and Control of Power Networks with Energy Storage (STABLE-NET)

Lead Research Organisation: Imperial College London
Department Name: Electrical and Electronic Engineering

Abstract

Summary:
The operations of interconnected power networks are facing unprecedented challenges which are primarily driven by new intermittent sources of generation that are replacing centralised flexible generation. Such intermittency in generation inevitably leads to difficulties in achieving reliable operation. The existing weak high voltage AC system in China suffers from stability-related problems and as a result, in 2010 17% of the electricity produced in China's top 10 wind power bases was curtailed with curtailment reaching as much as 25% in the Gansu province. A single grid fault on the 24th of February 2011 caused the disconnection of 598 wind turbines in Northwest China, resulting in a system frequency dip of 0.178 Hz, highlighting the inadequacy of the control technology currently used. A similar incident of generation outage in the UK on the 2nd of September 2010 led to a rapid decline in frequency, which disconnected about 350 MW embedded generation (mainly wind) through the action of the rate of change of frequency (RoCoF) protection. These are two of the many incidents that highlight the need for new approaches in fast system monitoring for enhanced stability and control.
Energy storage is essential to address the balance between generation and demand at different time scales. However, the description of the dynamic performance of energy storage under varied loading, and their state of charge and health monitoring are currently open problems. Complex dynamic behaviour, such as hysteresis, may manifest in storage systems. Therefore it is not clear how storage may impact power system operation, particularly with respect to stability. There have been instances of loss of generation because of the inadequate control of the power converter interface between intermittent generation and network. When the existing power converter technology is duplicated to act as an interface between storage and the grid, the poor performance is inevitable without improved understanding of local and global dynamics. Another key barrier is the lack of robust enabling technology for monitoring and control that can integrate the capabilities of storage in a time critical manner. Fast dynamic security assessment has been attempted through the energy function approach - but existing tools fail to compute the true stability margin because of the complexity of power system dynamic characteristics. All these barriers may be overcome through underpinning research in monitoring, modelling and control of storage to stabilise interconnected power network operations.

The challenges lie in fast computation, fault detection and robust control design of the interface between storage and the network. The approach proposed here is decentralised stability monitoring, assessment and control of the network. Existing network operation practice relies heavily on slow and centralised control architectures through large SCADA/EMS. The methodologies that are being proposed will thus need to rely little on system wide communication infrastructure. In addition, distributed approach to dynamic system monitoring, decentralised approaches to system wide disturbances and dynamic security assessment through distributed energy function are novel approaches. The innovations include cutting edge representations of high power low energy storage; energy functions to include asynchronous and synchronous generation with storage with resistive elements, practical applications of ground breaking decentralised fault detection and robust and reliable control between intermittent generation and the rest of the system.

Because the successful operation of interconnected power grids requires fast computation and control, as well as energy storage domain knowledge, the power system and energy storage experts in this consortium are joined by a number of leading control theory experts with experience in power networks - definitely a very unique strength of the team.

Planned Impact

Impact Summary
Distributed control and monitoring of power grids incorporating storage is the way forward to address the intermittency of renewable generation. This will make the large population of China more energy secure and drive developments in new technology, plus it will generate huge opportunities for business and communities through enhanced economic activities.
In the UK, China and many other countries worldwide, control and computation are driving smart grid development. Network operators such as National Grid, UK and the State Grid Corporation in China (SGCC) and power and control equipment vendors such as Alstom Grid (UK and China) and ABB are clear beneficiaries as is expressed in their strong support for this proposal. Many of the investigators on both the UK and Chinese side already enjoy healthy collaborative working relationships with industrial and utility partners, primarily within their own countries. This programme will undoubtedly deliver greater bilateral exchange.
The UK Government in 2011 recognised the need for more than £110 billion investment by 2020 to build and reinforce its electricity generation and grid infrastructure. A significant part of this investment will be in transmission monitoring and control, and storage. The Chinese government has enacted a plan to develop smart grid technology. China's national utility, the State Grid Corporation of China (SGCC), announced plans to invest $250 billion in electric power infrastructure upgrades over the next five years, of which $45 billion is earmarked for smart grid technologies. Another $240 billion between 2016 and 2020 will be added to complete the smart grid project. A large number of skilled researchers who will be trained in this project will have opportunities to technically lead future projects in the respective country.
In the short to medium term this project will establish and strengthen the collaborations between the leading UK and Chinese universities engaged in research in power system stability and control theory applications for grid integration of renewable energy and storage. This will pave the way to further strengthen and expand the volume of activities through future research funding opportunities involving both countries because of the degree of challenge and opportunities afforded by power grids in both the countries.
As described in the case for support, the consortium partners from both sides bring a range of theoretical, application and laboratory experience and expertise in the areas of control theory, computation, power system stability, monitoring, renewable energy and storage into the proposal. There are differences in the approaches to power network design, control and operation and specifications on the operational performance of control devices in the UK compared to China. This will lead to novel scientific understanding validated on different contexts and systems which could not be possibly achieved by either side working in isolation. The range of such advances is detailed in the proposal. The academic advances include new models, control and monitoring algorithms, and optimal allocations of storage.
The consortium proposes a sound research exchange and dissemination plan through conferences, panel sessions in top conferences such as the IEEE Power and Energy Society General Meeting, the IEEE Conference on Decision and Control and others. The UK side of the consortium has two IEEE Transactions Editors-in-Chief (Control Systems Technology and Sustainable Energy) so the academic impact of this research is going to be high. Industrial impact is also evident given that two of the investigators hold industry chairs (Thornhill and Parisini) and the PI has worked on a number of research projects funded fully by European power industries. The China side has several technology leaders and is well connected with industry, similarly to their UK counterpart, as demonstrated by the track records and industry support.

Publications

10 25 50
 
Description The project had multiple research themes involving network modelling, identification, stability, storage modelling , integration and control.
1. Our work has focused on implementing battery models within state estimation schemes to provide improved state of charge (SOC) and other estimates relevant for grid energy storage. We have concentrated on both equivalent circuit models (ECMs) and electrochemical models. Key results are (i) that the observability of nonlinear ECMs is different to the observability of the linearised model, and this must impact the choice of filter (e.g. EKF vs. UKF), particularly when we wish to estimate sensor bias as well as other states, (ii) that we can design an observer (in the form of an EKF) for the full electrochemical lithium-ion battery model, allow state estimation of all electrochemical states and (iii) under high C-rates (perhaps more than 5 C), the performance of the single particle model in an observer allows only around 90% accuracy on SOC estimation compared to the full model.
The SOC model now is included for calculating true worth from storage device for network services

2. A scalable distributed method for the monitoring of Large-Scale Systems with application to a Power Networks model, proposing a Decision Support System for the reconfiguration of the control after the occurrence of faults.

3. A distributed state estimation method for Large-Scale Systems using Sensor Networks, based on a multi-objective optimization framework.

4. A procedure for the definition of the optimal topology for distributed monitoring architectures for Large-Scale Systems.
5. We have developed a tool based on fourth order moment that deals with non-Gaussian error on the measurement data used to identify the inception of disturbance in multivariate framework.

5. A method, based on the framework of differential games, which ensures stability of a DC microgrid given that a disturbance has perturbed the system from its nominal operating condition.
6. The development of differential games with underlying communication graphs, which are applicable to large-scale power systems.
7. A method for obtaining approximate solutions for the mixed H2/H-infinity control problem for nonlinear systems: this allows us to design controllers which ensure that both robustness and optimality properties are satisfied and is useful, among other applications, for power systems.
8. A non linear fault identification method has been customised to suit to power system
9. A Test Model of a Power Grid with Battery Energy Storage and Wide-Area Monitoring,
Exploitation Route 1. The condition monitoring algorithm will be useful tools for battery designers
2. Multivariate approach to fault detection is useful for network fault management - our project partner ABB has shown interest in that.
3. Test model for power transmission network with storage will inspire the next generation researchers to develop and validate their methods
Sectors Aerospace, Defence and Marine,Education,Energy

 
Description Several patents have been utilized by industries in China.
Sector Education,Electronics,Energy
Impact Types Societal,Economic,Policy & public services

 
Description Provided training to engineers from TNB Malaysia
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact The engineers have advanced themselves through further knowledge of the field
URL http://www.imperial.ac.uk/people/b.pal
 
Description Training to Engineers from Power Industry in Chile
Geographic Reach Multiple continents/international 
Policy Influence Type Influenced training of practitioners or researchers
Impact The engineers from grid operator in Chile have now much advanced knowledge about power system and wind energy modelling
URL https://www.linkedin.com/in/bikash-pal-0ba3a413/
 
Description NIA Funding
Amount £225,000 (GBP)
Organisation National Grid UK 
Sector Private
Country United Kingdom
Start 07/2014 
End 12/2016
 
Description Network Innovation allowance
Amount £70,000 (GBP)
Organisation UK Power Networks 
Sector Private
Country United Kingdom
Start 10/2016 
End 03/2018
 
Description A Decentralized Fault-Tolerant Control scheme based on Active Fault Diagnosis 
Organisation University of Pavia
Department Department of Electrical, Computer and Biomedical Engineering
Country Italy 
Sector Academic/University 
PI Contribution Use of the active fault-diagnosis tool in a decentralized scenario for large-scale interconnected systems. Novel Fault-Tolerant Control strategy for interconnected systems. Application in a Power Network Systems simulation model.
Collaborator Contribution An active-fault diagnosis tool
Impact One conference publication and one journal paper in preparation
Start Year 2015
 
Description Anomaly detection for a synchronous-machine dynamic model 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution Novel observer-based anomaly detection method for nonlinear systems in a decentralized scenario.Design of an anomaly detection threshold both in the case of bounded uncertainties and stochastic uncertainties (even non-Gaussian case).
Collaborator Contribution Decentralized model of a synchronous-machine dynamic model Simulation experiments
Impact It is a multi-disciplinary collaboration involving Control-theory and Power Systems. A paper has been published this year on the IEEE Transactions on Power Systems.
Start Year 2016
 
Description Decentralized control and monitoring of Multi-Agent systems 
Organisation University of Modena and Reggio Emilia
Department Department of Sciences and Methods for Engineering
Country Italy 
Sector Academic/University 
PI Contribution Experience in distributed and decentralized methods for state estimation and fault detection. A decentralized estimation method for multi-agent systems, not requiring communication among leader agents. A decentralized fault detection and isolation method for Multi-agent systems.
Collaborator Contribution Experience in Multi-Agent systems control. Analysis of the convergence of the estimation error. Simulation results
Impact 2 conference publications and 1 under-review journal paper
Start Year 2014
 
Description Distributed estimation methods using Sensor Networks 
Organisation Royal Institute of Technology
Department ACCESS Linnaeus Center
Country Sweden 
Sector Academic/University 
PI Contribution Novel Pareto optimal state estimation and prediction method using sensor networks and its application for Fault detection. Extension to the non-completely-measurable state scenario and to the case of interconnected subsystems.
Collaborator Contribution Background about sensor networks, distributed estimation tools and distributed optimization.
Impact 2 conference publications and one under-review journal paper.
Start Year 2012
 
Description Estimation methods for Power systems models with Non-Gaussian noises 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution Development of a method for state estimation and anomaly detection under the presence of stochastic non-gaussian noises.
Collaborator Contribution Case-study scenario; model of the power system; simulations
Impact multi-disciplinary: control theory and power systems. Preparation of a draft paper to be submitted to IEEE Transactions on Power Systems.
Start Year 2018
 
Description Machine learning methods for demand estimation and privacy 
Organisation Royal Holloway, University of London
Country United Kingdom 
Sector Academic/University 
PI Contribution Initial discussion about machine learning methods for classification and prediction
Collaborator Contribution Demand models; problem formulation
Impact Initial report
Start Year 2018
 
Description STK- Manitoba HVDC 
Organisation Manitoba Hydro International Ltd.
Country Canada 
Sector Private 
PI Contribution I (Stefanie Kuenzel) have now joined Royal Holloway, University of London as Lecturer. During my time at Imperial under this grant, I had regular contact with Manitoba HVDC, including many technical discussions. Leading on from this project we have been working on another related proposal. Due to the technical engagement I had with Manitoba HVDC, they have offered support for our next proposal, including a significant cash contribution, support in kind and commercial licences.
Collaborator Contribution Manitoba HVDC met with me (Stefanie Kuenzel) several times throughout the project, this included many technical discussions. They have offered support for our next proposal, including a significant cash contribution, support in kind and commercial licences.
Impact They have offered support for our next proposal, including a significant cash contribution, support in kind and commercial licences.
Start Year 2013
 
Description Scalable monitoring of interconnected stochastic systems 
Organisation Polytechnic University of Milan
Country Italy 
Sector Academic/University 
PI Contribution Novel fault detection method for interconnected stochastic systems using a threshold based on the stochastic properties of an observer-based residual signal. Application of the proposed method on a Power Networks System simulation model and analysis.
Collaborator Contribution Scalable distributed state estimation method, allowing the estimate of a bound for the estimation error variance
Impact One conference publication and one under-review journal publication.
Start Year 2016
 
Description Scalable monitoring of interconnected stochastic systems 
Organisation Swiss Federal Institute of Technology in Lausanne (EPFL)
Department Automatic Control Laboratory
Country Switzerland 
Sector Academic/University 
PI Contribution Novel fault detection method for interconnected stochastic systems using a threshold based on the stochastic properties of an observer-based residual signal. Application of the proposed method on a Power Networks System simulation model and analysis.
Collaborator Contribution Scalable distributed state estimation method, allowing the estimate of a bound for the estimation error variance
Impact One conference publication and one under-review journal publication.
Start Year 2016
 
Description Scalable monitoring of interconnected stochastic systems 
Organisation University of Padova
Department Department of Information Engineering
Country Italy 
Sector Academic/University 
PI Contribution Novel fault detection method for interconnected stochastic systems using a threshold based on the stochastic properties of an observer-based residual signal. Application of the proposed method on a Power Networks System simulation model and analysis.
Collaborator Contribution Scalable distributed state estimation method, allowing the estimate of a bound for the estimation error variance
Impact One conference publication and one under-review journal publication.
Start Year 2016
 
Title Spectral li-ion SPM 
Description Spectral li-ion SPM is a MATLAB code that solves the so-called lithium-ion battery Single Particle Model (SPM) using spectral numerical methods. The SPM is an electrochemical model describing lithium transport, reaction kinetics and thermodynamics in lithium-ion batteries. Spectral li-ion SPM consists of the SPM coupled to a bulk thermal model describing the evolution of battery temperature. The SPM is an approximation to the electrochemical pseudo-two dimensional lithium-ion battery model where electrolyte transport limitations are neglected. 
Type Of Technology Physical Model/Kit 
Year Produced 2016 
Impact We have received a number of emails and enquiries about the software tool from users around the world. People are using it to understand and model lithium-ion cells. 
URL https://github.com/adrienBizeray/Spectral_li-ion_SPM
 
Description 14th European Control Conference, Linz, Austria (ECC 2015) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Paper presentation "A Distributed Pareto-Optimal Dynamic Estimation Method"
Year(s) Of Engagement Activity 2015
 
Description 15th European Control Conference, Aalborg, Denmark (ECC 2016) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Presentation of the paper results "Distributed Fault Detection with Sensor Networks using Pareto-Optimal Dynamic Estimation Method"
Year(s) Of Engagement Activity 2016
 
Description 3rd International Conference on Control and Fault-Tolerant Systems, Barcelona, Spain 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Conference talk to present publication results about "Decentralized Fault Diagnosis for Heterogeneous Multi-Agent Systems"
Year(s) Of Engagement Activity 2016
 
Description 53rd IEEE Conference on Decision and Control, Los Angeles, California (CDC 2014) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Presentation of the paper "Fault Diagnosis and Control-reconfiguration in Large-scale Systems: a Plug-and-Play Approach"
Year(s) Of Engagement Activity 2014
 
Description 9th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes, Paris, France (Safeprocess 2015) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact Presentation of the paper results
"Optimal Topology for Distributed Fault Detection of Large-scale Systems"
"A Plug-and-Play Fault Diagnosis Approach for Large-Scale Systems"
Year(s) Of Engagement Activity 2015
 
Description IEEE HVDC working group activities 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Kuenzel is an active member in two IEEE working groups on "Practical Technologies for VSC HVDC Systems" and "Planning for HVDC". In 2015 she became part of a subgroup of the working groups, putting together a one day tutorial for the IEEE PES GM 2016. This was delivered and very well received. As a result, the proposal to repeat the tutorial in 2017 has been granted. Preparations for this tutorial were agreed during the last working group meeting, which was hosted by Dr Kuenzel at her new post at Royal Holloway University of London, Feb 2017.
Year(s) Of Engagement Activity 2015,2016,2017
 
Description IFAC Safeprocess 2015 pre-workshop tutorial 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact IFAC Safeprocess 2015 pre-workshop tutorial about "Plug-and-play control and monitoring of large-scale systems", given with Prof. G. Ferrari-Trecate, from EPFL, during the 9th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes, held in Paris, France.15 researchers attended the workshop. It was an opportunity for discussion and questions. The audience was very interested.
Year(s) Of Engagement Activity 2015
 
Description Seminar Ruhr-Universität Bochum 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Seminar "Plug-and-Play Fault Detection and Control-reconfiguration for Large-scale Systems", Ruhr-Universität Bochum, Lehrstuhl für Automatisierungstechnik und Prozessinformatik, Bochum, Germany. The seminar I gave was followed by discussion and questions. I visited the Control Institute of the University and I had the opportunity to discuss about research with many members of the group.
Year(s) Of Engagement Activity 2015
 
Description Seminar Tsinghua University 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Seminar "Plug-and-Play methods for the monitoring of Large-Scale Systems", Center for Intelligent and Networked Systems, Department of Automation, Tsinghua University, Beijing,China. The seminar was followed by questions and discussions and the visit of the laboratories.
Year(s) Of Engagement Activity 2015