Conceptual Design and Simulation (WP1)

WP 1 will address the primary issue of characterising the behaviour of power systems with many small DERs connected. Alternative concepts/network topologies need to be articulated together with their operational characteristics and an initial technical assessment. In particular, this research will provide valuable new output profiles, demonstrate the behaviour of many small DERs in simulation and contribute analytical tools in support of operational planning.

HDPS - System Level Concept Definition

This discussion paper has been prepared by members of the UK Engineering and Physical Sciences Research Council (EPSRC) Supergen 3 HDPS consortium . It builds upon the initial concepts presented in a previous document by drawing upon experience gained by the consortium over the subsequent period in which the project has been active.

G. Strbac, "Electric power systems research on dispersed generation", Electric Power Systems Research, Vol. 77, No.9, pp.1143-1147, July 2007

Historically, distributed (or dispersed) generation (DG) has been of modest significance and the issues related to the techni- cal and commercial integration of this generation in the power system operation and development have received little attention. Over the last several years this has been rapidly changing due to a number of economic, technical, commercial and environmen- tal factors surrounding the electricity industry. These include introduction of competition in the industry, advances in devel- opments of small-scale generation technologies, availability of access to sites and fuel, aging infrastructure, etc...

G. Strbac, N. Jenkins and T. Green, "Future network technologies", Contribution to Energy Review, April 2006

The overall aims of this work are to review the key characteristics and limitations of the existing network operation and design philosophies and examine possible future developments of electricity transmission and distribution network technology in the context of alternative (extreme) electricity generation scenarios in the medium and long term. This work also includes quantitative analysis of benefits and costs of the integration of distributed generation in the operation and development of the future UK electricity system.

M. Thomson and D.G. Infield, "Network power-flow analysis for high-penetration distributed micro-generation", IEEE Transactions on Power Systems, vol. 22, pp. 1157-1162, 2007

Increasing numbers of very small generators are being connected to electricity distribution systems around the world. Examples include photovoltaics (PV) and gas-fired domestic-scale combined heat and power (micro-CHP) systems, with electrical outputs in the region of 1 to 2 kW. These generators are normally installed within consumers’ premises and connected to the domestic electricity supply network (230 V single-phase in Europe, 120 V in North America). There is a growing need to understand and quantify the technical impact that high penetrations of such generators may have on the operation of distribution systems. This paper presents an approach to analyzing this impact together with results indicating that considerable penetrations of microgeneration can be accommodated in a typical distribution system.

M. Thomson and D.G. Infield, "Impact of widespread photovoltaics generation on distribution systems", IET Renewable Power Generation, vol. 1, pp. 33-40, 2007

Prompted by the need for clean energy sources, increasing numbers of photovoltaic (PV) generators are being connected to electricity distribution systems around the world. There is thus a growing imperative to understand and quantify the technical impact that high penetrations of such generators may have on the operation and performance of electricity distribution systems. Detailed simulations of a very high penetration of PV within a typical UK urban distribution network (11 kV, 400 V and 230 V) are reported. The study performed unbalanced three-phase load-flow analysis on an entire feeder within a time-domain simulation framework using load and generation data at 1 minute intervals. The results indicate that even at very high penetrations of PV, network voltage rises are small and unlikely to cause problems. Effects on network power flows and losses are also quantified and discussed.

I. Richardson, M. Thomson and D.G. Infield, "A high-resolution domestic building occupancy model for energy demand simulations", Energy and Buildings Volume 40, Issue 8, 2008, pp 1560-1566

Energy use in the home is a major source of carbon emissions and is highly dependent on the activities of the residents. More specifically, the timing of energy use, particularly electricity, is highly dependent on the timing of the occupants’ activities. Thus, in order to model domestic demand profiles with high temporal resolution, for example, in the context of designing and assessing demand side management systems (including the time-shifting of demand), it is of great benefit to take account of residents’ behaviour in terms of when they are likely to be using household appliances, lighting and heating. This paper presents a thorough and detailed method for generating realistic occupancy data for UK households, based upon surveyed time-use data describing what people do and when. The approach presented generates statistical occupancy time-series data at a ten-minute resolution and takes account of differences between weekdays and weekends. The model also indicates the number of occupants that are active within a house at a given time, which is important for example in order to model the sharing of energy use (shared use of appliances, etc.) The data from the model can be used as input to any domestic energy model that uses occupancy time-series as a base variable, or any other application that requires detailed occupancy data. The model has been implemented in Excel and is available for free download.

A.S.Emhemed, G. Burt, O. Anaya-Lara, "Impacts of high penetration of single-phase distributed energy resources on the protection of LV distribution networks", 42nd International Universities Power Engineering Conference, 4-6 Sept. 2007, pp 223-227

In the future millions of homes in the UK may have the appropriate characteristics to facilitate the deployment of existing micro CHP technologies, and establish "personal power stations", using different types of distributed energy resources (DERs). The micro CHP technologies to be accommodated at houses are typically driven by single-phase generators at 230 V. However, the integration of a large number of such single-phase generators may lead to changes in the behaviour of the system in both normal and abnormal operation. This paper focuses on investigating the performance of an LV distribution network with high penetration of DERs under abnormal conditions. For this investigation the DERs are based on directly- connected single-phase generators and converter-connected generation. The contribution of these sources to network fault levels and their impact on overcurrent protection schemes are assessed in order to outline the protection requirements in future LV distribution networks with active power sources located at each home.

P. Djapic, C. Ramsay, D. Pudjianto, G. Strbac, J. Mutale, N. Jenkins, R. Allan, "Taking an active approach", Power and Energy Magazine, IEEE Volume 5, Issue 4, July-Aug. 2007 Page(s):68 - 77

The United Kingdom is leading Europe in its power market reforms and is currently engaged in addressing issues of DG integration through development of innovative approaches to network planning, operation, regulation, and pricing. This article draws on these recent advances to explore active management technologies, developing regulatory arrangements for network operation, and new commercial opportunities emerging from the low-carbon climate change agenda. It explores the changing role of the distribution system operator (DSO) in response to increasing penetration of DG and identifies the transitions currently taking place in the United Kingdom toward integration of DG that has wider implications for extrapolation across Europe.

N.J. Kelly, I. Beausoleil-Morrison, "Specifications for Modelling Fuel Cell and Combustion-Based Residential Cogeneration Devices within Whole-Building Simulation Programs", IEA ECBCS Annex 42 Subtask B Report, ISBN 978-0-662-47116-5, 2007

This document contains the specifications for a series of residential cogeneration device models developed within IEA/ECBCS Annex 42.

N.J. Kelly, I. Beausoleil-Morrison, "Experimental Investigation of Residential Cogeneration Devices and Calibration of Annex 42 Models", IEA Energy Conservation in Buildings and Community Systems Programme ISBN 978-0-662-47924-6, 2008

This report documents the experimental investigations of residential cogeneration systems conducted within Annex 42 and the subsequent calibration of the Annex 42 models using these data.

M. Thomson, "High-Density Micro-Generation in UK Distribution Networks", International Conference and Workshop on Micro-Cogeneration Technologies and Applications, Ottawa, Canada, 2008.

The widespread introduction of micro-generation in homes and small commercial premises could have significant technical impacts on the operation of local distribution networks. Detailed modelling of such generation, particularly micro-cogeneration (known in the UK as micro combined heat and power – micro- CHP) and solar photovoltaics (PV) has been completed and a discussion of the key results is presented. The modelling covers a significant area of UK distribution network (over 1000 properties) and employs unbalanced load-flow analysis within a time-domain simulation framework. Both generation and demand are represented with a one-minute time resolution and are stochastic and diverse as expected in real networks. The results include quantification of voltage rise, reverse power flow, altered transformer and line loadings and altered losses.

A. Ferguson, N. Kelly ,A. Weber and B. Griffith, "Calibration and validation of a combustion cogeneration model", Proc. eSim 2008 , The 5th IBSPA-Canadian Conference, Quebec City, May 21-22, 2008

 

D. Beyer and N.J. Kelly, "Modelling the Behaviour of Domestic Micro-Co-Generation under Different Operating Regimes and with Variable Thermal Buffering", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

This paper describes the preliminary outcomes from a comprehensive modelling exercise that explored the performance of domestic cogeneration for different UK housing types under different operational scenarios, and with and without thermal buffering. The simulation results indicate that thermal buffering has a dramatic effect on the performance and operational characteristics of micro-cogeneration devices however, due to standing losses in the thermal buffering, carbon emissions levels show only small variations.

C.N.Jardine, "Synthesis of high resolution domestic electricity load profiles", First International Conference and Workshop on Micro-Cogeneration Technologies and Applications National Arts Centre, Ottawa, Ontario, 2008

A novel method of synthesising high-resolution domestic electricity loads has been developed in order to provide the necessary accuracy to a forthcoming network model. It is based on measured 30 minute resolution data of household loads and average appliance usage. The model utilises an occupancy model, which can serve as a proxy for both non- baseload electricity demand and heat demand. Synthesised ‘activity’ profiles were then generated for a sample of 1000 homes. The 30 minute appliance data provides the probability that an appliance will be on. With knowledge of appliance ownership levels, typical appliance power and the ‘activity’ profiles, appliance turn-on events can be triggered, and load profiles built up for each dwelling. Behavioural characteristics, relating to the number of appliances owned, rated power of these appliances, and how often they are used, are also included to replicate the variability in electricity consumption observed between houses.

N. J. Kelly, S. Galloway I. Elders R.M.Tumilty and G.M.Burt, "Modelling the Imapct of Micro Generation on the Electrical Distribution System", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

In the UK and elsewhere there is considerable debate as to the future form of the electricity distribution system. The coming years will see a rise in the amount of micro-generation connected to the network at low voltages and the emergence of highly-distributed power systems (HDPS). However, there is considerable uncertainty as to the impact that this micro-generation will have on the quality of power supplied to our homes or to the stability of the electricity system as a whole. To address these engineering challenges the UK Engineering and Physical Sciences Research Council (EPSRC) is funding a three year research programme featuring a multi-disciplinary team from a variety of UK Universities: Supergen HDPS. This paper documents one piece of work emerging from the consortium, where a multi-tool approach is used to analyse the impact of micro-generation on the electricity system. This used a building simulation tool to produce electrical generation profiles for domestic cogeneration device models. These, along with profiles produced for other micro-generation technology models and electrical load profiles are then replicated and aggregated using a customised statistical approach. The profiles were then used as boundary conditions for a set of electrical load flow simulations on a model of a section of real network, where the number of micro- generators was varied according to different scenarios for the future of the UK electricity grid. The results indicate that a significant number of micro-generation devices can be accommodated before any power quality problems arise, however this is dependent upon maintaining a robust central grid.

N.J. Kelly, A. Ferguson, B. Griffith and A. Weber, "The Development of a Generic Systems-Level Model for Combustion-Based Domestic Cogeneration", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

A long established and appropriate means to evaluate the energy performance of buildings and their energy systems is through the use of dynamic building simulation tools. However, until now, only a very limited number of micro-cogeneration device models have been available to the modelling community and generally these have not been appropriate for use within building simulation codes. This paper describes work undertaken within the International Energy Agency’s Energy Conservation in Building and Community Systems Annex 42 to address this problem through the development of a generic, combustion- based cogeneration device model that is suitable for integration within building simulation tools and can be used to simulate the variety of Internal Combustion Engine (ICE) and Stirling Engine (SE) cogeneration devices that are and will be available for integration into dwellings.

Y. Lei, G. Burt, O. Anaya-Lara, J. McDonald, "Aggregated modelling of distributed networks with distributed generation", Universities Power Engineering Conference, 2007. UPEC 2007. 42nd International, 4-6 Sept. 2007, pp 837 - 841

A new methodology to derive an aggregated model representation of a distributed network with distributed generation (DG) is presented. The network includes small-scale wind turbines based on induction generators, distribution lines, transformers, reactive power compensation devices, such as capacitors, and low voltage feeders. This aggregated model is employed to analyse induction generators starting up currents and short circuit fault currents. The study is conducted in Matlab/Simulink and simulation results that illustrate the adequacy of the proposed methodology are presented and discussed.

Y. Lei, G. Burt, A. Dysko, "Analysis of Parallel-Operated Single-Phase Self-Excited Induction Generators", 19th International Conference on Electricity Distribution, Vienna, 21-24 May 2007

In this paper, a new methodology is presented to analyse the parallel operation of single-phase self-excited induction generators (SEIGs) in a distribution system. The model is then employed by analyzing starting currents and short circuit currents contributions from the SEIGs. Relevant simulation and analysis are performed using Matlab/Simulink. It is found that the aggregation model proposed in this paper can give satisfactory results.

R.M. Tumilty, A.S. Emhemed, A. Rafa, O. Anaya-Lara and G.M. Burt, "Microgeneration transient stability investigation report", Report for Centre for Sustainable Electricity and Distributed Generation

 

Emhemed, A.S.; Tumilty, R.M.; Burt, G.M.; McDonald, J.R.; "Transient performance analysis of low voltage connected microgeneration", Conversion and Delivery of Electrical Energy in the 21st Century, 2008 IEEE 20--24 July 2008 Page(s):1 - 6

The growing awareness of the environmental impacts of large-scale thermal generating units has stimulated interest in microgeneration that is installed within domestic or commercial premises. This paper investigates the transient response to be expected from a range of microgeneration units that could typically be connected. The paper examines the impact of fault locations, typical fault clearance times and generator/prime mover technologies on the ability of microgenerators to maintain stability when subject to disturbances during and after clearing of both local low and remote medium voltage faults. The paper also presents the study of the step voltage changes occurring due to the simultaneous reconnection of a large number of microgenerators within a small area of the network. Two types of technologies are considered in this paper: a small diesel engine driving a three-phase synchronous machine connected within commercial premises; and a small microwind turbine interfaced directly within a residential dwelling by a single-phase induction generator.

R.M. Tumilty, A.S. Emhemed, O. Anaya-Lara, G.M. Burt, J.R. McDonald, "Adaptive unit based MV protection for actively managed distribution networks", Proceedings of the IEEE-Mexico Power Engineering Summer Meeting, RVP-AI 2007, Acapulco, Mexico, July 2007.

Electricity networks are extensive, well established and a key part of the infrastructure that supports industrialised society. These networks are moving from a period of stability to a time of potentially major transition. This change is being driven by a need for age-related renewal on a large scale, governmental policy commitments to harness cleaner and renewable sources of electricity generation and power industry structural changes. This paper seeks to identify the need for an evolution towards active distribution networks and innovations in electricity transportation.

Emhemed, A.S.; Tumilty, R.M.; Burt, G.M.; McDonald, J.R.; "Transient performance analysis of single-phase induction generators for microgeneration applications", Power Electronics, Machines and Drives, 2008. PEMD 2008. 4th IET Conference on 2-4 April 2008

This paper presents studies of a single-phase induction machine driven by a micro wind turbine connected to an LV distribution system within a residential dwelling. The transient associated with grid connection and both local and electrically remote network faults are presented. Based on these studies conclusions will be drawn regarding the network impacts of microgenerators using single-phase induction generators and, conversely, the impact of network secondary systems such as protection (e.g. typical fault clearance times) on the behaviour of these generators, and also the threshold values of the machine speed and its retained terminal voltage when the system experiences a remote fault on the MV system are defined. The principle contribution of this paper is to highlight stability issues associated with such small scale generators, and to propose some remedial measures by which the stable operation of such generators may be improved.

SuperGen 3: HDPS Poster

Thinking Networks poster providing an overview of the consortium's work.

SUPERGEN HDPS Scenarios

This paper presents a set of scenarios for use within the SUPERGEN consortium on highly distributed power systems. The scenarios have been designed to represent a variety of futures that will aid the consortium in their work. The scenarios are designed in such a manner that they will allow the consortium to test its key research questions, whilst providing a common basis for all research groups.

A.H. Rafa, O. Anaya-Lara, J.R. McDonald, "Stability Assessment of Microgeneration Systems", Power Electronics, Machines and Drives, 2008. PEMD 2008. 4th IET Conference, 2-4 April 2008, pp 265 - 269

Microgeneration technologies connected to low-voltage distribution networks, such as small-scale wind turbines, Photovoltaic (PV) arrays and micro combined heat and power (uCHP) offer the potential to reduce carbon emissions, to improve security of supply. These technologies can be based on either synchronous or asynchronous generators, although many of them are connected to the network via power electronic interfaces. Although the use of microgeneration provides many benefits it also imposes various challenges with regards to stability, control and protection. In particular, this paper investigates the transient behaviour of induction generator-based microgeneration in the event of a shortcircuit fault. The influence of synchronous generator and converter-connected microgeneration on the dynamic performance of the induction generator is also investigated. The investigations were conducted in PSCAD/EMTDC.

Y. Lei, R.M. Tumilty, G. M. Burt and J. R. McDonald, "Performance of induction generator protection during distribution network disturbances", Developments in Power System Protection, 2008, IET 9th International Conference, pp. 529-534, 17-20 March 2008

Distributed generators (DGs) that are rated between several kVA and 25OkVA in size are increasingly being connected at the 400V electrical distribution level. Therefore, new requirements for the traditional network protection schemes and the co-ordination between network protection and intertie protection are needed. Actual problems have been experienced relating to DG transient behaviour, thereby, more accurate analysis is required. This paper presents studies using a real time simulation platform to investigate the transient behaviour of the distributed generators' protection under external disturbances. Furthermore, an optimized DG protection setting for keeping most of the DG stable under such disturbances is proposed.

L. Peeters, N.J. Kelly and W. D`haeseleer, "Thermal comfort in residential buildings with water based heating systems: a tool for selecting appropriate heat emitters when using micro-cogeneration", Proc. Microgen 2008, Ottawa Apr 29-May 1, 2008

As a consequence of people becoming more aware of their impact on the environment, there is an increasing demand for low energy buildings. Forced by regulation, building envelopes are improving and heating and cooling systems with higher efficiencies are being installed. The public are willing to embrace these new technologies, as long as they do not affect the quality of their indoor environment. In this paper, an introduction to research on the realisation of the indoor thermal comfort in residential buildings with water based, low-energy heating systems is given. The basis for this work is a more realistic definition of comfort temperatures for residential buildings. Subsequently, appropriate heat emitters to realise that thermal comfort in an efficient way are identified, taking into account the limitations of the production system under consideration. An example of a µ-cogeneration system is presented as a case study.

N.F.Silva and G.Strbac, "Strategic investment in distribution networks with high penetration of small scale distributed energy resources", 19th International Conference on Electricity Distribution, Session 4. Paper No 0687. pp 1/4, Vienna, 21-24 May 2007

In contrast with traditional approaches to optimal network design based either on the analysis of a small specific area or on idealistic networks, the proposed method determines optimal network design policies by evaluating alternative strategies on many statistically similar networks. The software is then a statistical assessment of a number of hypothetical but realistic networks (consumers distributions, types, numbers, network length, components, number of substations, etc), created using the concepts of fractal theory. Evaluating the cost of each particular design over a number of statistically similar networks allows statistically significant conclusions to be drawn. Modelling each load individually will reveal problematic operating conditions which were not considered when using a smooth load profile. Thus, each and every domestic load was represented by a different load profile and the impact on losses was evaluated. The software tool also allows the simulation of penetration of micro generation such as CHP and PV in the realistic distribution networks to determine the effect of DG in the LV system.

D.Cao, D.Pudjianto, S.Grenard and G.Strbac, "Benefits of active voltage controls in distribution networks", 42nd International Universities Power Engineering Conference, 2007, 7-9 Sept. 2005.

 

G.Strbac, P.Djapic, T.Bopp and N.Jenkins, "Benefits of active mangement of distribution systems", Wind Power in Power Systems,Published Online: 28 Oct 2005

Distributed generation (DG); wind power; active management techniques; voltage rise effect; active power generation curtailment; reactive power compensation; Base case scenarios; cost-benefit analysis (CBA); OLTC transformer voltage control

R.Allan, P.Djapic and G.Strbac, "Methodology for assessing security contribution from distributed generation", Proceedings of the 3rd IEE International Conference on Reliability of Transmission and Distribution Networks, RTDN, London, 2005

The paper presents and discusses the fundamental assumptions and features of the methodology for assessing security contribution from distributed generation. The paper also provides numerical studies where the effects of various parameters are studied.

D. Pudjianto, G. Strbac, F. van Overbeeke, A.I. Androutsos, Z. Larrabe and J. Tome Saraiva, "Investigation of Regulatory, Commercial, Economic and Environmental Issues in MicroGrids", Future Power Systems, 2005 Intl Conference,Page(s) :6, 16-18 Nov 2005

Concepts of MicroGrids are proposed to address primarily various issues related to integration of small scale renewables and increased demand of reliable electricity supply. With an active management control approach and ability to operate in islanding mode, a cluster of micro generators, electricity storage and electrical loads can be operated within the MicroGrids framework to provide higher supply reliability to highly value customers. Solutions are required not only to make these concepts technologically feasible and safe to operate but also to be commercially viable and attractive, economically efficient and supported by electricity regulations. This paper summarises the results of investigations on various economic, regulatory and commercial issues faced by the development of MicroGrids in MICROGRIDS project. The potential economic benefits and contributions to environment from applications of MicroGrid technologies are also presented and described in this paper.

G. Strbac, C. Ramsay, D. Pudjianto, "Integration of distributed generation into the UK power system", Contribution to Energy White paper, PublishedMarch 2007

This White Paper, published on 23 May 2007, sets out the Government’s international and domestic energy strategy to respond to changing circumstances, address the long term energy challenges we face and deliver our energy policy goals.

B. Boardman et al., "Home Truths A low carbon strategy to reduce UK housing emissions by 80% by 2050", Friends of the Earth

The Low-carbon Strategy from the Environmental Change Institute at Oxford University identifies the policies needed to deliver an 80 per cent cut in carbon emissions from UK homes by 2050. These cuts are achievable but will require a quantum leap in commitment from Government and a radical new approach. The policies have been designed not only to dramatically reduce carbon emissions, but also to be delivered equitably. The poorest households will be prioritised for assistance and fuel poverty will be wiped out. The scientific consensus is that for the UK to play its part in helping the world avoid a rise of more than 2°C, we must reduce our carbon emissions by 80 per cent by 2050. The household sector represents 27 per cent of our total emissions and achieving deep cuts here is an imperative. The low-carbon revolution starts at home.

C.N.Jardine, "Performance of West Oxforsdhire District Council Office's Photovoltaic Arrays", PVSAT3, Durham, 2007

The West Oxfordshire District Council office building in Witney contains 23 kWp of building integrated photovoltaic arrays across 6 different roofs, each with different pitches and orientations. Two roofs face NNE and WNW, and so do not receive direct sunshine throughout the course of the year. The building is seen as an important test of the effects of non-optimal orientations as part of the Field Trial process, although it is acknowledged that electricity yields will never reach optimal levels.