http://hdl.handle.net/10197/3091 2013-05-18T15:23:42Z http://hdl.handle.net/10197/3598 Rotor angle stability with high penetrations of wind generation Vittal, Eknath; O'Malley, Mark; Keane, Andrew This paper explores the relationship between wind generation, particularly the control of reactive power from variable speed wind turbine generators, and the rotor angle stability of the conventional synchronous generators in the system. Rotor angle stability is a dynamic phenomenon generally associated with changes in active power flows that create angular separation between synchronous units in the system. With larger penetrations of wind generation being introduced into power systems, there will be large flows of active power from asynchronous generation in the system. These asynchronous active power flows can aid in maintaining the rotor angle stability of the system. However, the manner in which wind generation injects reactive power into the system can be critical in maintaining angular stability of the synchronous units. Utilizing wind generation to control voltage and reactive power in the system can ease the reactive power burden on synchronous generators, and minimize angular separation in the system following a contingency event and can provide a significant level of support which will become increasingly important in future power systems. 2012-02-01T00:00:00Z http://hdl.handle.net/10197/3597 Minimising transmission reactive support required by high penetration of distributed wind power distribution Ochoa, Luis; Keane, Andrew; Dent, Chris; Harrison, Gareth Wind power generation is the fastest growing renewable technology worldwide with large on- and off-shore wind farms being connected to the transmission networks. A significant share of it, however is still being deployed at distribution levels. While distributed wind generation presents traditionally passive distribution networks with well-established technical challenges, reactive support needed by high penetrations of such new generation capacity might also have an impact on the week areas of the transmission grid. In this work, a multi-period AC optimal power flow-based technique is proposed to find power factor and substation settings that minimise the transmission reactive support required by variable distributed generation while also considering N-1 contingencies. A section of Irish distribution network is analysed. Results show the significant benefits that a passive approach such as the use of optimal power factor and substation settings can achieve. 2011-11-01T00:00:00Z http://hdl.handle.net/10197/3584 A study of optimal non-firm wind capacity connection to congested transmission systems Burke, Daniel J.; O'Malley, Mark As wind is a low capacity factor source of power generation, a non-physically-firm connection strategy is key to its cost-effective and timely integration to presently constrained transmission networks. This paper therefore outlines the design and study of an optimal non-firm wind capacity allocation model. While a precise statistical representation of wind power variations and geographical inter-dependency requires a significant number of data samples, the structured very-large-scale linear programming problem that results is shown to be exploitable by the Benders’ decomposition scheme. Various wind capacity target levels are considered, and important sensitivity analyses performed for multiple load profiles, wind profiles, and fuel price parameter values. Interestingly, the optimal wind capacity allocation is found to be reasonably robust to sizeable load and fuel price deviations, and while the effect of a limited historical wind data profile is more influential, the associated cost-function penalty is not significantly critical. The economic value of combining wind connection with advanced post-contingency network remedial action schemes is also highlighted. 2011-04-01T00:00:00Z http://hdl.handle.net/10197/3583 Impact of wind power on the unit commitment, operating reserves, and market design Kiviluoma, Juha; O'Malley, Mark; Tuohy, Aidan; Meibom, Peter; Milligan, Michael R.; Lange, Bernard; Holttinen, Hannele; Gibescu, Madeleine This article highlights and demonstrates the new requirements variable and partly unpredictable wind power will bring to unit commitment and power system operations. Current practice is described and contrasted against the new requirements. Literature specifically addressing questions about wind power and unit commitment related power system operations is surveyed. The scope includes forecast errors, operating reserves, intra-day markets, and sharing reserves across interconnections. The discussion covers the critical issues arising from the research. Paper presented at the 2011 IEEE Power and Energy Society General Meeting, San Diego, CA, 24-29 July 2011 2011-07-24T00:00:00Z http://hdl.handle.net/10197/3576 The role of power system flexibility in generation planning Lannoye, Eamonn; Flynn, Damian; O'Malley, Mark As the penetration of variable renewable generation increases in power systems worldwide, planning for the effects of variability will become more important. Traditional capacity adequacy planning techniques have been supplemented with integration studies, which have been carried out in power systems with high targets for renewable generation. These have highlighted the increased variability that a system may experience in the future. As system planning techniques evolve with the demands from variable generation, the flexibility of a system to manage periods of high variability will need to be assessed. A metric may be required to measure the flexibility of a power system for use in planning studies with multi-year horizons. Compared to generation adequacy metrics, system flexibility assessment is more data intensive and requires more detailed system modeling. An algorithm for scenario development in generation planning with high penetrations of variable generation is presented. Paper presented at the IEEE 2011, Power and Energy Society General Meeting, San Diego, CA, 24-29 July 2011 2011-07-24T00:00:00Z http://hdl.handle.net/10197/3575 A flexible power system operations simulation model for assessing wind integration Ela, Erik; Milligan, Michael R.; O'Malley, Mark With the advent of wind power generation on worldwide power systems, many operators and researchers are analyzing the impacts that higher future amounts may have on system operations. Many of the tools are analyzing longer term impacts on the steady-state operations of power systems and are primarily using cost as a metric. They are also using tools that are often inflexible to accommodating different market designs or operational structures. In this paper a model was developed to mimic operator behavior using a combination of security-constrained unit commitment, security-constrained economic dispatch, and automatic generation control programs. New metrics are used to compare reliability in terms of energy imbalance for different systems or different market and operational structures at very high time resolution. Finally an example application of the tool and results for a test system are shown. Paper presented at the IEEE 2011, Power and Energy Society General Meeting, San Diego, CA, 24-29 July 2011 2011-07-24T00:00:00Z http://hdl.handle.net/10197/3553 Frequency dynamics during high CCGT and wind penetrations Meegahapola, Lasantha; Flynn, Damian Frequency stability is the paramount concern for secure and reliable operation of a power system. High wind penetration levels are reported in power systems with high thermal generation, and hence its likely to result high wind and combined-cycle gas turbine (CCGT) penetrations during system operation since CCGTs are the most preferable choice for the thermal generation. The doubly-fed induction generators (DFIGs) do not provide any inertial response while the CCGTs have unique frequency response during the system frequency disturbances. Therefore, CCGT turbine response characteristics and the zero inertial response may influence on frequency dynamics of a power network. The main objective of this study is to analyze the frequency dynamics during generator outages and three-phase short-circuit faults in a power network with high CCGT and wind penetrations. A test network model was developed based on the Northern-Ireland network in DIgSILENT Power Factory software package. It has shown that frequency stability may be threatened when three-phase short circuit faults occur in power networks during high CCGT and wind penetrations which may lead to CCGT combustor lean-blowout and ultimately results large frequency excursions in the network. Presented at AUPEC 2011, Australasian Universities Power Engineering Conference, Brisbane, Australia, 25 - 28 September 2011 2011-01-01T00:00:00Z http://hdl.handle.net/10197/3548 System-wide inertial response from fixed speed and variable speed wind turbines Ruttledge, Lisa; Flynn, Damian As wind penetration levels on power systems increase worldwide, the dynamic characteristics of these systems are changing due to the displacement of synchronous generation. One issue, of particular concern, is the resulting reduction in system inertia. Modern, variable speed wind turbines are controlled by power electronics and so do not inherently contribute to the inertial response of the system. Such devices can however be fitted with a control loop which provides an active power response to significant frequency deviations, similar to the inertial response of fixed speed wind turbines and synchronous generation. However, the response of variable speed turbines is dependent on local wind speeds and so cannot be quantified deterministically by system operators. This paper examines the potential for wind generation to contribute to system inertial response and considers the aggregated inertial response capabilities of fixed speed and variable speed wind generation. IEEE PES 2011 General Meeting, Detroit, Michigan, USA, July 24-28, 2011 2011-07-24T00:00:00Z http://hdl.handle.net/10197/3544 Challenges posed by the integration of wave power onto the Irish power system Kavanagh, David; Keane, Andrew; Flynn, Damian In order to gauge the potential impact of wave power in Ireland, the capacity factor of theoretical wave farms deployed at various locations around the Irish coast is compared to the system-wide capacity factor of wind power generation over the same period. It is shown that wave power off the coast of Ireland experiences a very significant seasonal variation, but with a lower daily variation. This paper presents the results of that analysis and examines certain challenges that will face the Irish power system if a large portfolio of wave power devices is deployed. Issues such as system adequacy and the capacity value of wave power are discussed. Paper presented at the 9th European Wave and Tidal Energy Conference, Southampton, UK, 5–9th September, 2011 2011-09-05T00:00:00Z http://hdl.handle.net/10197/3543 A study of principal component analysis applied to spatially distributed wind power Burke, Daniel J.; O'Malley, Mark Multivariate dimension reduction schemes could be very useful in limiting the number of random statistical variables needed to represent distributed wind power spatial diversity in transmission integration studies. In this paper, principal component analysis (PCA) is applied to the covariance matrix of distributed wind power data from existing Irish wind farms, with the eigenvector/eigenvalue analysis generating a lower number of uncorrelated alternative variables. It is shown that though uncorrelated, these wind components may not necessarily be statistically independent however. A sample application of PCA combined with multivariate probability discretization is also outlined in detail. In that case study, the capability of PCA to reduce the number and prioritize the order of the alternative statistical variables is key to potential wind power production costing simulation efficiency gains, when compared to exhaustive multiyear time series load flow investigations. 2011-11-01T00:00:00Z http://hdl.handle.net/10197/3542 Aspects of wind energy characteristics in transmission related optimisation models : invited panel discussion paper Burke, Daniel J.; O'Malley, Mark This invited panel paper discussion will outline a number of aspects of wind energy characteristics relevant to the optimal wind/transmission model formulation task. Optimal placement of wind capacity on a constrained transmission network is a typical example of this type of problem. In particular the relevance of advanced and computationally intensive stochastic unit commitment to the model formulation will be debated. Optimization constraint matrix structure and techniques to exploit it will be shown to be of considerable importance for this type of problem. The relative merits of different model dimensionality reduction schemes, either through multivariate component analysis and probability discretisation or indeed scenario reduction, will be discussed. A pragmatic acceptance of the imprecise impact of long-term power system uncertainties will be maintained throughout, and wherever possible generality to different types of power systems will be considered. Presented at the IEEE Power and Energy Society General Meeting, Detroit, USA, 24-29 July 2011 2011-07-24T00:00:00Z http://hdl.handle.net/10197/3435 Integration of variable generation : capacity value and evaluation of flexibility Lannoye, Eamonn; Milligan, Michael R.; Adams, John; Tuohy, Aidan; Chandler, Hugo; Flynn, Damian; O'Malley, Mark As integration of variable generation continues to grow rapidly in power systems globally, system planners are seeking new tools to understand the role of variable output generators and the challenges experienced with their integration. The North American Electric Reliability Corporation (NERC) has established a task force to examine the integration of variable generation. This paper details the achievements to date and outlines ongoing efforts from Task 1.2 on the capacity value of variable generation and from Task 1.4 on the concept of flexibility in power systems and options for its definition. Arising from international collaboration with the International Energy Agency, a discussion on the definition of flexible resources is presented. A potential metric for flexibility offered by conventional plant is developed and applied to a test system. Paper presented at the IEEE Power and Energy Society (PES) 2010 General Meeting, July 25-29 2010, Minneapolis, Minnesota 2010-07-01T00:00:00Z http://hdl.handle.net/10197/3434 Varying penetration ratios of wind turbine technologies for voltage and frequency stability Vittal, Eknath; Keane, Andrew; O'Malley, Mark This paper examines the ability of a power system to accommodate wind generation with varying ratios of doubly fed induction generator and fixed speed induction generator turbines from both static and dynamic aspects. By controlling the ratio between the two types of turbines, voltage stability is maintained for steady-state conditions for a large range of varying wind speeds. Using the ratio determined from the static analysis, the dynamic analysis explores the voltage and frequency characteristics of the system under contingency conditions. An initial analysis was carried out on the IEEE 30 bus test system. The results of this analysis are presented in this paper and detail how by varying the ratio of the turbine types the frequency stability and voltage stability can be improved. Paper presented at the IEEE Power and Energy Society 2008 PES General Meeting - Conversion and Delivery of Electrical Energy in the 21st Century, 20-24 July 2008, Pittsburgh, PA, USA 2008-07-01T00:00:00Z http://hdl.handle.net/10197/3433 Impact of pumped storage on power systems with increasing wind penetration Tuohy, Aidan; O'Malley, Mark In this paper, the unit commitment and dispatch of a power system with and without a pumped storage unit is examined for increasing levels of installed wind power, from 17% of total energy to 80% of total energy generated by wind 3 (3GW to 15GW of installed wind on the Irish system in 2020). At high levels of installed wind, it is shown that storage reduces curtailment and increases the use the base loaded plant on the system. This reduces system costs. However, when the additional capital costs of storage are taken into account, it is shown that storage is not viable from a system perspective until extremely large levels of wind power are seen on the system. At these levels of installed wind, while the system can operate without storage, it is less costly to do so with storage. The capacity credit of the storage unit is also examined, using a simplified approach, and shown to decrease as larger amounts of intermittent wind power are added to the system. Paper presented at IEEE Power & Energy Society General Meeting, July 26-30, 2009, Calgary, Canada 2009-07-01T00:00:00Z http://hdl.handle.net/10197/3432 Demand side resource operation on the Irish power system with high wind power penetration Keane, Andrew; Tuohy, Aidan; Meibom, Peter; Denny, Eleanor; Flynn, Damian; Mullane, Alan; O'Malley, Mark The utilisation of demand side resources is set to increase over the coming years with the advent of advanced metering infrastructure, home area networks and the promotion of increased energy efficiency. Demand side resources are proposed as an energy resource that, through aggregation, can form part of the power system plant mix and contribute to the flexible operation of a power system. A model for demand side resources is proposed here that captures its key characteristics for commitment and dispatch calculations. The model is tested on the all island Irish power system, and the operation of the model is simulated over one year in both a stochastic and deterministic mode, to illustrate the impact of wind and load uncertainty. The results illustrate that demand side resources can contribute to the efficient, flexible operation of systems with high penetrations of wind by replacing some of the functions of conventional peaking plant. Demand side resources are also shown to be capable of improving the reliability of the system, with reserve capability identified as a key requirement in this respect. 2011-05-01T00:00:00Z http://hdl.handle.net/10197/3388 Optimal charging of electric vehicles in low-voltage distribution systems Richardson, Peter; Flynn, Damian; Keane, Andrew Advances in the development of electric vehicles, along with policy incentives will see a wider uptake of this technology in the transport sector in future years. However, the widespread adoption of electric vehicles could lead to adverse effects on the power system, especially for existing distribution networks. These effects would include excessive voltage drops and overloading of network components, which occur mainly during periods of simultaneous charging of large numbers of electric vehicles. This paper demonstrates how controlling the rate at which electric vehicles charge can lead to better utilisation of existing networks. A technique based on linear programming is employed, which determines the optimal charging rate for each electric vehicle in order to maximise the total power that can be delivered to the vehicles while operating within network limits. The technique is tested on a section of residential distribution network. Results show that, by controlling the charging rate of individual vehicles, high penetrations can be accommodated on existing residential networks with little or no need for upgrading network infrastructure. 2011-06-23T00:00:00Z http://hdl.handle.net/10197/3353 Capacity value of wind power Keane, Andrew; Milligan, Michael R.; Dent, Chris; Hasche, Bernhard; D'Annunzio, Claudine; Dragoon, Ken; Holttinen, Hannele; Samaan, Nader; Söder, Lennart; O'Malley, Mark Power systems are planned such that they have adequate generation capacity to meet the load, according to a defined reliability target. The increase in the penetration of wind generation in recent years has led to a number of challenges for the planning and operation of power systems. A key metric for generation system adequacy is the capacity value of generation. The capacity value of a generator is the contribution that a given generator makes to generation system adequacy. The variable and stochastic nature of wind sets it apart from conventional energy sources. As a result, the modeling of wind generation in the same manner as conventional generation for capacity value calculations is inappropriate. In this paper a preferred method for calculation of the capacity value of wind is described and a discussion of the pertinent issues surrounding it is given. Approximate methods for the calculation are also described with their limitations highlighted. The outcome of recent wind capacity value analyses in Europe and North America, along with some new analysis are highlighted with a discussion of relevant issues also given. 2011-05-01T00:00:00Z http://hdl.handle.net/10197/3339 Transmission connected wind curtailment with increasing wind capacity connection Burke, Daniel J.; O'Malley, Mark Many countries have ambitious plans to increase wind energy penetration levels in the near future. With a low capacity factor and even lower capacity credit, wind power is a fundamentally different power generation source than conventional plant. Traditional planning methodologies focusing solely on the impact of turbine capacity’s impact on line flow worst-case scenarios may unnecessarily impede cost-effective wind integration. This paper assesses the impact of increased wind capacity connection on wind energy curtailment indices using a security-contrained optimal power flow model. Results indicate significant scope for increased wind capacity connection exists if small levels of wind energy curtailment are accepted. Paper presented at IEEE Power & Energy Society General Meeting, July 26-30, 2009, Calgary, Canada 2009-07-01T00:00:00Z http://hdl.handle.net/10197/3338 Stochastic analysis of the impact of electric vehicles on distribution networks Richardson, Peter; Taylor, Jason; Flynn, Damian; Keane, Andrew Advances in the development of electric vehicles, along with policy incentives, will see a wider uptake of this technology in the transport sector in future years. However, large penetrations of EVs could lead to adverse effects on power system networks, especially at the residential distribution network level. These effects could include excessive voltage drop and thermal loading of network components. A stochastic method is developed to take account of the uncertainties associated with EV charging and the technique is implemented on a residential test network using power system simulation software. The results show how voltage levels, component loading network losses are impacted from EV charging, taking into account the probabilistic behaviour of the EV owners. Paper presented at CIRED 2011, the 21st International Conference on Electricity Distribution, Frankfurt, 6-9 June 2011 2011-06-01T00:00:00Z http://hdl.handle.net/10197/3337 Quantifying reserve demands due to increasing wind power penetration Doherty, Ronan; O'Malley, Mark With wind power penetration increasing in many systems worldwide, operational issues are beginning to emerge due to the uncertain nature of wind power. One of these issues is the provision of reserve for system security. To analyse this, one must consider generator outage rates, system load forecast errors and wind power forecast errors in such a way as to directly relate the system reserve level to the security of the system. In this paper a new methodology is proposed for the analysis and provision of system reserve levels. The methodology considers the provision of both reserve (on-line) and replacement reserve (offline). The proposed methodology is then applied to the IEEE reliability test system incorporating other influencing factors like wind farm size and numbers and forecast periods. Results illustrate the impact increasing wind power penetration has on reserve. Paper presented at the IEEE Bologna Power Tech Conference, Bologna, Italy, June 23-26th, 2003 2003-06-01T00:00:00Z http://hdl.handle.net/10197/3336 A non-linear operator based method for harmonic feature extraction from speech signals Kavanagh, Darren F.; Boland, Frank An important pre-processing stage in speech recognition systems is that of extracting phonetically pertinent acoustic features from the speech signal. These features form the basis for discriminative classification and serve as cues for the identification of phonetic events in speech. The paper addresses this by presenting a novel method for the classification of harmonic (short-term periodic) and non-harmonic segments in speech signals. Classification is accomplished by proposing two new features derived from the non-linear Teager energy operator (TEO). The features proposed are the TEO-Weighted Harmonic Product (TEO-WHP*)and the TEO-Weighted Harmonic Sum (TEO-WHS*). Experiments are reported and discussed that demonstrate the effectiveness and the importance of these features as a valuable preprocessor for many speech systems. Paper presented at the IEEE International Conference on Signal Processing and Communications (ICSPC 2007), 24-27 November 2007, Dubai, United Arab Emirates 2007-11-01T00:00:00Z http://hdl.handle.net/10197/3318 Rolling unit commitment for systems with significant installed wind capacity Tuohy, Aidan; Denny, Eleanor; O'Malley, Mark As wind power penetration grows, the amount of reserve needed on the system also grows, due to the increases in the uncertainty of wind power, which grows larger as forecast horizon increases. By scheduling the system more often the amount of extra reserve to be carried to cater for wind uncertainty decreases, depending on the flexibility of plant on the system. This reduces the costs of operating the system. There is a trade off between reduced costs due to more frequent commitment, the ability of wind forecasts to be made more accurately, and the increased costs of more flexible plant. This paper examines the benefits of committing the system more frequently, and how different factors such as reliability of the system, accuracy of the forecasts and plant mix impact on this. Paper presented at IEEE Power Tech 2007, 1-5 July, 2007, Lausanne, Switzerland 2007-07-01T00:00:00Z http://hdl.handle.net/10197/3317 Passive and active kinesthetic perception just-noticeable-difference for natural frequency of virtual dynamic systems Li, Yanfang; Israr, Ali; Patoglu, Volkan; O'Malley, Marcia This paper investigates the just-noticeable-difference (JND) for natural frequency of virtual second order dynamic systems. Using a one degree-of-freedom haptic device, visual and/or haptic sensory feedback were presented during interactions with the system. Participants were instructed to either perceive passively or actively excite the system in order to discriminate natural frequencies. The JND for this virtual resonance task ranged from 3.99% to 6.96% for reference frequencies of 1 Hz and 2 Hz. Results show that sensory feedback has a significant effect on JND in passive perception, with combined visual and haptic feedback enabling the best discrimination performance. In active perception, there is no significant difference on JND with haptic and combined visual and haptic feedback. There is also no significant difference between active perception and passive perception for this JND experiment. The presentation of systems with equivalent natural frequencies but different spring stiffness resulted in no large bias toward larger stiffness and no significant difference in JND for equivalent systems. This finding indicates that human participants do not discriminate natural frequency based on the maximum force magnitude perceived, as indicated by prior studies. Paper presented at the Symposium on Haptic Interfaces for Virtual Environments and Teleoperator Systems 2008 13-14 March, Reno, Nevada, USA 2008-03-01T00:00:00Z http://hdl.handle.net/10197/3316 Optimal firm wind capacity allocation to power systems with security constraints Burke, Daniel J.; O'Malley, Mark Many countries have declared future renewable energy penetration targets. Wind power connection to power systems is delayed by limited transmission system capacity as attractive wind sites are often located in weakly designed transmission areas. Optimal use of existing transmission system resources should be made in the allocation of capacity connection permits. The volume of wind power connection applications and their power production statistical inter-dependencies suggest that they should be assessed in a collective probabilistic manner. This paper uses a sequential probabilistic load flow method in tandem with a linear programming computational geometry constraint redundancy approach to optimally allocate wind capacities given the transmission system capacity that is securely available. Paper presented at the 2009 IEEE PES Power Systems Conference & Exhibition, March 15-18 2009, Seattle, Washington 2009-03-01T00:00:00Z http://hdl.handle.net/10197/3315 Optimal distributed generation plant mix with novel loss adjustment factors Keane, Andrew; O'Malley, Mark The distributed generation (DG) plant mix connected to any network section has a considerable impact on the total amount of DG energy exported and on the amount of losses incurred on the network. A new method for the calculation of loss adjustment factors (LAFs) for DG is presented, which determines the LAFs on a site specific and energy resource specific basis. A mixed integer linear program is formulated to optimally utilise the available energy resource on a distribution network section. The objective function incorporates the novel LAFs along with individual generation load factors, facilitating the determination of the optimal DG plant mix on a network section. Results are presented for a sample section of network illustrating the implementation of the optimal DG plant mix methodology for two representative energy resource portfolios. Paper presented at the IEEE PES General Meeting 2006, Montreal, Quebec, Canada, 18-22 June 2006 2006-06-01T00:00:00Z http://hdl.handle.net/10197/3314 Modernising and rationalising the first course in power systems on the island of Ireland O'Dwyer, Jeremiah; Flynn, Damian; Keane, Andrew; O'Malley, Mark The two largest Universities on the Island of Ireland both have significant power system activities. As part of a major all-island initiative these two groups are working more closely on joint research and educational activities. Here the first courses on power systems in the two institutions are described as part of a process which is planned to bring more co-ordination between the power system activities on the Island of Ireland. Paper presented at the 2007 Power Engineering Society General Meeting, 24-28 June, Tampa, Florida 2007-06-01T00:00:00Z http://hdl.handle.net/10197/3310 Impact of distributed generation capacity on losses Keane, Andrew; O'Malley, Mark The introduction of distributed generation (DG) onto distribution networks has a significant effect on losses. This effect cannot be characterised as detrimental or beneficial but is dependent on the allocation of DG on each distribution network section. Here the impact of DG on losses has been modelled, facilitating a unique approach to the allocation of DG. This approach has been implemented and tested on sample sections of distribution network and results are presented showing the optimal allocation of DG which improves the efficiency of energy delivery on the distribution network. The temporal variations of load and generation are simulated, illustrating that the allocation improves the efficiency throughout a year. The effect of different plant mixes is also simulated showing that the efficiency of energy delivery is dependent on the load factor and operating characteristic of the plant. Paper presented at the IEEE PES General Meeting 2006, Montreal, Quebec, Canada, 18-22 June 2006 2006-06-01T00:00:00Z http://hdl.handle.net/10197/3306 Functionally biarticular control for smart prosthetics Gillespie, Brent; Baker, J.; O'Malley, Marcia; Shewokis, Patricia; Contreras-Vidal, Jose Luis In this paper we introduce the use of force feedback in conjunction with myoelectric control to establish an improved interface for a powered prosthetic limb. The force feedback is delivered through a single-axis exoskeleton worn about the elbow, while the EMG signal is derived from the biceps muscle. This combination is intended to produce a sense of effort in the biceps that is associated with the action of the motorized prosthetic gripper. The method engages both efferent and afferent signals innervating a functional muscle with the aim of realizing a muscle that is effectively biarticular. The controlling muscle spans one joint physiologically and a second, prosthetic joint functionally. Preliminary experiments have demonstrated that force feedback can substitute for vision during grasp and lift tasks. Paper presented at the Third Joint Eurohaptics Conference and Symposium on Haptic Interfaces for Virtual Environment and Teleoperator Systems Salt Lake City, UT, USA, March 18-20, 2009 2009-01-01T00:00:00Z http://hdl.handle.net/10197/3305 Factors influencing wind energy curtailment Burke, Daniel J.; O'Malley, Mark Nonphysically firm wind generation connections (i.e., those to which curtailment can apply) may be necessary for significant wind integration to congested transmission networks. A study of factors influencing this associated wind energy curtailment is, therefore, of timely importance. In this paper, the wind curtailment estimation effects of natural inter-yearly wind profile variability, system demand-profile/fuel-price parameter uncertainty, and minimum system inertial constraints are studied in detail. Results indicate that curtailment estimation error can be reduced by appropriate wind data year-length and sampling-rate choice, though a pragmatic consideration of system parameter uncertainty should be maintained. Congestion-related wind energy curtailment risk due to such parameter uncertainty exhibits appreciable interlocational dependency, suggesting there may be scope for effective curtailment risk management. The coincidence of wind energy curtailment estimated due to network thermal congestion and system wide inertial-stability issues also has commercial significance for systems with very high wind energy penetration targets, suggesting there may be appreciable interaction between different sources of curtailment in reality 2011-04-01T00:00:00Z http://hdl.handle.net/10197/3304 Evolution of operating reserve determination in wind power integration studies Ela, Erik; Kirby, Brendan; Lannoye, Eamonn; Milligan, Michael R.; Flynn, Damian; Zavadil, Bob; O'Malley, Mark The growth of wind power as an electrical power generation resource has produced great benefits with reductions in emissions and the supply of zero cost fuel. It also has created challenges for the operation of power systems arising from the increased variability and uncertainty it has introduced. A number of studies have been performed over the past decade to analyze the operational impacts that can occur at high penetrations of wind. One of the most crucial impacts is the amount of incremental operating reserves required due to the variability and uncertainty of wind generation. This paper describes different assumptions and methods utilized to calculate the amount of different types of reserves carried, and how these methods have evolved as more studies have been performed. Paper presented at the IEEE Power and Energy Society (PES) 2010 General Meeting, July 25-29 2010, Minneapolis, Minnesota 2010-07-01T00:00:00Z http://hdl.handle.net/10197/3303 Effect of energy harvesting network reactive support on transmission system voltage performance Cuffe, Paul; Smith, Paul; Keane, Andrew It is common to operate distributed generators (DGs) at fixed inductive power factors to overcome voltage rise constraints on distribution networks. This approach increases distribution system reactive power demand, which may strain transmission system reactive power resources at times of system-wide high DG output, particularly if such output displaces synchronous generators. If a number of adjacent DGs are connected to a transmission node in a clustered fashion via a dedicated energy harvesting network (EHN), it is possible to characterise their aggregated reactive power capability as a form of virtual power plant. Such a characterisation will be provided in this paper. The aggregated capability may readily be included in transmission system models. This work will explicitly compare the transmission system voltage-control performance of EHN reactive capability with that of traditional synchronous plant. Paper presented at the 21st International Conference on Electricity Distribution, Frankfurt, June, 6-9, 2011 2011-06-01T00:00:00Z http://hdl.handle.net/10197/3302 Application of wind generation capacity credits in the Great Britain and Irish systems Dent, Chris; Bialek, Janusz W.; Hasche, Bernard; Keane, Andrew The concept of capacity credit is widely used to quantify the contribution of renewable technologies to securing demand. This may be quantified in a number of ways; this paper recommends the use of Effective Load Carrying Capability (ELCC, the additional demand which the new generation can support without increasing system risk), with system risk being measured using Loss of Load Expectation (LOLE, this is calculated through direct use of historic time series for demand and wind load factor). The key benefit of this approach is that it automatically incorporates the available statistical information on the relationship between wind availability and demand during the hours of very high demand which are most relevant in assessing system adequacy risk. The underlying assumptions are discussed in detail, and a comparison is made with alternative calculation approaches; a theme running through the paper is the need to consider the assumptions carefully when presenting or interpreting risk assessment results. A range of applications of capacity credits from Great Britain and Ireland are presented; this includes presentation of effective plant margin, ensuring that the optimal plant mix secures peak demand in economic projection models, and the Irish capacity payments system. Finally, new results comparing capacity credit results from the Great Britain and Irish systems using the same wind data are presented. This allows the various factors which influence capacity credit results to be identified clearly. It is well known that increasing the wind load factor or demand level typically increases the calculated capacity credit, while increasing the installed wind capacity typically decreases its capacity credit (as a percentage of rated capacity). The new results also show that the width of the probability distribution for available conventional generating capacity, relative to the peak demand level, also has a strong influence on the results. This emphasises further that detailed understanding of risk model structures is vitally important in practical application. Paper presented at Cigre 2010, 22nd to 27th August 2010, Paris, France 2010-01-01T00:00:00Z http://hdl.handle.net/10197/3301 A quantitative analysis of the net benefits of grid integrated wind Denny, Eleanor; Bryans, Garth; Fitz Gerald, John; O'Malley, Mark Throughout the world significant development is being encouraged in wind energy for electricity generation. A complete cost and benefit analysis has been conducted in this paper on grid connected wind generation. It takes into account system costs such as reserve requirements, start-up and ramping implications for conventional plants as well as wear and tear costs. The benefits of wind generation analysed include the emissions benefits, the saving on the fuel bill, the electricity generated and the capacity value. These costs and benefits are then used to generate net benefit curves for wind generation and the sensitivities of the curves are tested with changes in the underlying assumptions. A complete unit commitment model with wind generation is used to determine the dispatches upon which the costs and benefits are calculated. Paper presented at the IEEE PES General Meeting 2006, Montreal, Quebec, Canada, 18-22 June 2006 2006-06-01T00:00:00Z http://hdl.handle.net/10197/3281 New tool for integration of wind power forecasting into power system operation Gubina, Andrej F.; Keane, Andrew; Meibom, Peter; O'Sullivan, Jonathan; Goulding, Oisin; McCartan, Tom; O'Malley, Mark The paper describes the methodology that has been developed for Transmission System Operators (TSOs) of Republic of Ireland, Eirgrid, and Northern Ireland, SONI the TSO in Northern Ireland, to study the effects of advanced wind power forecasting on optimal short-term power system scheduling. The resulting schedules take into account the electricity market conditions and feature optimal reserve scheduling. The short-term wind power prediction is provided by the Anemos tool, and the scheduling function, including the reserve optimisation, by the Wilmar tool. The proposed methodology allows for evaluation of the impacts that different types of wind energy forecasts (stochastic vs. deterministic vs. perfect) have on the schedules, and how the new incoming information via in-day scheduling impacts the quality of the schedules. Within the methodology, metrics to assess the quality of the schedules is proposed, including the costs, reliability and cycling. The resulting schedules are compared to the Day-ahead and In-day results of the existing scheduling methodology, Reserve Constrained Unit Commitment (RCUC), with the historical data used as the input for calibration. Paper presented at the IEEE PowerTech 2009 conference, Bucharest, June 28 2009-July 2 2009 2009-06-01T00:00:00Z http://hdl.handle.net/10197/3280 Ireland's Smart Grid demonstration projects McGranaghan, M. F.; Fallon, T.; Keane, Andrew Paper presented at the Protection, Automation and Control (PAC) World Conference, 21 to 24 June 2010, Trinity College, Dublin 2010-06-01T00:00:00Z http://hdl.handle.net/10197/3279 Impacts of large amounts of wind power on design and operation of power systems, results of IEA collaboration Holttinen, Hannele; Meibom, Peter; Orths, Antje; O'Malley, Mark; Ummels, Barth; Tande, John Olav; Estanqueiro, Ana; Gomez, Emilio; Smith, J. Charles; Ela, Erik There are a multitude of studies made and ongoing related to cost of wind integration. However, the results are not easy to compare. An international forum for exchange of knowledge of power system impacts of wind power has been formed under the IEA Implementing Agreement on Wind Energy. IEA WIND R&D Task 25 on “Design and Operation of Power Systems with Large Amounts of Wind Power” has produced a state of the art report in October 2007, where the most relevant wind power grid integration studies are analysed especially regarding methodologies and input data. This paper summarises the results from 18 case studies with discussion on the differences in the methodology as well as issues that have been identified to impact the cost of wind integration. Paper presented at the 7th International Workshop on Large-Scale Integration of Wind Power into Power Systems as well as on Transmission Networks for Offshore Wind Farms, Madrid, Spain, 26-27 May, 2008 2008-05-01T00:00:00Z http://hdl.handle.net/10197/3278 Evaluating which forms of flexibility most effectively reduce base load cycling at large wind penetrations Troy, Niamh; Denny, Eleanor; O'Malley, Mark Increasing penetration of wind power on power systems worldwide is resulting in the unconventional operation of base-load generating units. These units which were originally designed for operation at full output are more frequently required to balance the variability of the wind. This results in increased start-stop cycling and hours at low load which causes severe deterioration to the plants components. Interconnection, storage and demand side management increase the flexibility of a power system and can balance variations in the wind power output, thus reducing the onus on thermal plants. This study will attempt to quantify which of these forms of flexibility is most effective at reducing base-load cycling on a thermal test system with a large amount of wind. Paper presented at the 8th International Workshop on Large-Scale Integration of Wind Power into Power Systems, 14-15 October 2009, Bremen, Germany 2009-10-01T00:00:00Z http://hdl.handle.net/10197/3277 Analysis of the voltage control capability of energy harvesting networks Cuffe, Paul; Smith, Paul; Keane, Andrew At times of high generation levels from distributed generators (DGs), there may be a paucity of conventional generators still synchronised to the transmission system. These synchronous machines have traditionally been the power system's principal source of controllable reactive power. If DGs are operated at inductive power factors, total reactive power absorption at distribution system bulk supply points may be highest at times when the transmission system is least equipped to supply it. On the Irish power system, new DGs (typically windfarms) may be connected in a clustered fashion to a new transmission node. This paper will show how the aggregate reactive power capabilities of these clustered DGs may be characterised. Of particular importance is how the cluster can respect distribution system operating limits while also providing reactive power support to the transmission system. Paper presented at the 9th International Workshop on Large-Scale Integration of Wind Power into Power Systems, 18-19 October 2010, Québec, Canada 2010-10-01T00:00:00Z http://hdl.handle.net/10197/3274 Operating the Irish power system with increased levels of wind power Tuohy, Aidan; Denny, Eleanor; Meibom, Peter; Barth, Rudiger; O'Malley, Mark This paper summarises some of the main impacts of large amounts of wind power installed in the island of Ireland. Using results from various studies performed on this system, it is shown that wind power will impact on all time frames, from seconds to daily planning of the system operation. Results from studies examining operation of the system with up to approximately 40% of electricity provided by wind show that some of the most important aspects to be considered include the type of wind turbine technology, the provision of reserve to accommodate wind forecasting error and the method used to plan plant schedules. Paper presented at the 2008 PES General Meeting, July 20-24, 2008, Pittsburgh, Pennsylvania 2008-07-01T00:00:00Z http://hdl.handle.net/10197/3272 Minimising transmission reactive support required by high penetration of distributed wind power generation Ochoa, Luis; Keane, Andrew; Dent, Chris; Harrison, Gareth Wind power generation is the fastest growing renewable technology worldwide with large on- and off-shore wind farms being connected to the transmission networks. A significant share of it is, however, still being deployed at distribution levels. While distributed wind generation presents traditionally passive distribution networks with well-established technical challenges, reactive support needed by high penetrations of such new generation capacity might also have an impact on the weak areas of the transmission grid. In this work, a multi-period AC optimal power flow-based technique is proposed to find power factor and substation settings that minimise the transmission reactive support required by variable distributed generation while also considering N-1 contingencies. A section of Irish distribution network is analysed. Results show the significant benefits that a passive approach such as the use of optimal power factor and substation settings can achieve. Paper presented at the 8th International Workshop on Large-Scale Integration of Wind Power into Power Systems, 14-15 October 2009, Bremen, Germany 2009-10-01T00:00:00Z http://hdl.handle.net/10197/3271 Improved system operations with high penetration of wind power : a dialog between academia and industry - Ireland Power, Michael; O'Malley, Mark This is a submission to a panel session at the 2010 IEEE PES General Meeting. It discusses effective collaboration between academia and industry. Panel session submission for the IEEE Power and Energy Society (PES) 2010 General Meeting, July 25-29 2010, Minneapolis, Minnesota 2010-07-01T00:00:00Z http://hdl.handle.net/10197/3268 A small - signal stability analysis of DFIG wind generation Vittal, Eknath; O'Malley, Mark; Keane, Andrew This paper examines the small-signal stability impacts of high penetrations of doubly-fed induction generator (DFIG) wind turbines on power systems. It provides a basic overview of small-signal stability concepts and then examines the response of DFIG generation to two local contingency event. Using the New England 39 bus test system, this paper will demonstrate the stability implications of DFIG turbines utilizing terminal voltage control and fixed power factor control in response to reactive and active power loss events. By implementing terminal voltage control strategies in DFIG wind turbines, system stability is improved and allows for increased levels of wind penetration levels while maintaining a high level of system security. Paper presented at the 8th International Workshop on Large-Scale Integration of Wind Power into Power Systems, 14-15 October 2009, Bremen, Germany 2009-10-01T00:00:00Z http://hdl.handle.net/10197/3267 Planning and operating non-firm distributed generation Keane, Andrew; Zhou, Qiong; Bialek, Janusz W.; O'Malley, Mark The penetration of Distributed Generation (DG) is increasing on distribution networks across the world. Non-firm access to the network is now being proposed as a cost effective way to facilitate DG. However, concerns remain about the operational details of non-firm access and also with regard to the financing of DG projects, which, by their nature, are not guaranteed permission to export power at all times. Here, the pertinent operational issues that arise with non-firm access are analysed. The index of coincidence is used to assess the probability of constraint breaches, through analysis of historical generation and load profiles. Further to this, a novel method is proposed, which minimises the cost to the generators of non-firm access through coordinated operation. 2009-12-01T00:00:00Z http://hdl.handle.net/10197/3266 Impact assessment of varying penetrations of electric vehicles on low voltage distribution systems Richardson, Peter; Flynn, Damian; Keane, Andrew Advances in the development of electric vehicles, along with policy incentives will see a wider uptake of this technology in the transport sector in future years. However, the widespread implementation of electric vehicles could lead to adverse effects on power system networks, especially existing distribution networks. This work investigates some of the potential impacts from various levels of uncontrolled electric vehicle charging on a test distribution network. The network is examined under worst case scenario conditions for residential electricity demand in an effort to assess the full impact from electric vehicles. The results demonstrate that even for relatively modest levels of electric vehicle charging, both the voltage and thermal loading levels can exceed safe operating limits. The results also indicate the importance of assessing each phase on the network separately in order to capture the full effects of uncontrolled electric vehicle charging on the network. IEEE Power and Energy Society (PES) 2010 General Meeting, July 25-29 2010, Minneapolis, Minnesota 2010-07-01T00:00:00Z http://hdl.handle.net/10197/3265 Ireland's approach for the connection of large amounts of renewable generation Smith, Paul; Cuffe, Paul; Grimes, Simon; Hearne, Tony This paper discusses the connection policies adopted to facilitate the large number of wind farms seeking access to the Irish power system. A key feature is a grouped connection offer process that provides certainty for wind project developers and optimises the development of the network. A further interesting feature is the development of a “wind cluster” concept which permits semi-dedicated MV networks for the connection of a group of adjacent wind farms, together with equitable arrangements for sharing the financial burden of construction between developers. IEEE Power and Energy Society (PES) 2010 General Meeting, July 25-29 2010, Minneapolis, Minnesota 2010-07-01T00:00:00Z http://hdl.handle.net/10197/3264 Managing wind uncertainty and variability in the Irish power system Tuohy, Aidan; Troy, Niamh; Gubina, Andrej F.; O'Malley, Mark This paper summarizes work that has been done to examine the impact of the uncertainty and variability of significant installed wind power on the Irish system. As more and more wind power is installed on the system, the operation of conventional plant on the system will be dramatically different. In this paper, three different aspects of the hour-to-hour operation of the Irish power system are examined. An innovative method to schedule the system is described, together with key results giving the effect of the uncertainty of wind on unit commitment of the system. The increased cycling of traditionally base-load units due to large amounts of wind power is quantified, and the steps to reduce this unwanted behavior are outlined. Finally, the use of intelligent decision tools based on sophisticated wind power forecasts for scheduling and provision of reserve is described. Paper presented at IEEE Power & Energy Society General Meeting, July 26-30, 2009, Calgary, Canada 2009-07-01T00:00:00Z http://hdl.handle.net/10197/3252 Building a sustainable energy future : supply and demand options Denny, Eleanor; O'Malley, Mark Fossil fuel depletion and concerns over global climate change are increasing the demand for sustainable and clean solutions for electricity generation. In the coming years some of the most difficult engineering challenges in history will have to be faced if a future with sustainable energy is to be developed. In light of this challenge investments in human infrastructure are essential in particular for early stage students who represent the generation who will have to truly solve future energy needs. This paper discusses an initiative in Ireland to foster an interest in energy issues for undergraduate students. A report made by the students on sustainable energy issues in Ireland is discussed here. The students focussed on recommendations that can be achieved in the short to medium term thus in many cases the infrastructural changes needed are simply a change in thinking or operational approach. One of the key infrastructural issues that arose is the importance of spatial planning in all areas of energy demand and supply. Paper presented at the 2008 PES General Meeting, July 20-24, 2008, Pittsburgh, Pennsylvania 2008-07-01T00:00:00Z http://hdl.handle.net/10197/3250 Effect of generator flow control strategies on the long term dynamics of a model for power systems Fitzmaurice, Ronan; Keane, Andrew; O'Malley, Mark Cascading component failure can cause system-wide blackouts in power systems. Complex system analysis of the long term dynamics suggests that power transmission systems operate near a critical point. Here the effect of generator operation in a model for power systems is investigated. Two opposing methods of dispatching generators are compared. These two methods are to minimize and maximize the line flows with respect to their limits across the system. These methods are also compared to an economic dispatch. It is shown that the generator dispatch method used affects the frequency distributions and other statistics of blackouts. Dispatching using the maximization method causes a reduction in the frequencies of all blackouts as measured by the amount of load shed. This reduction is concurrent with an increase in the investment in the transmission system. These observations suggest that economic dispatch, while attempting to increase reliability, actually decreases the robustness of the system. Paper presented at the 43rd Hawaii International Conference on System Sciences (HICSS-43), January 5-8, 2010, Kauai, Hawaii, USA 2010-01-01T00:00:00Z http://hdl.handle.net/10197/3249 Enhanced utilization of voltage control resources with distributed generation Keane, Andrew; Ochoa, Luis; Vittal, Eknath; Dent, Chris; Harrison, Gareth Distributed Generation (DG) is increasing in penetration on power systems across the world. In rural areas, voltage rise limits the permissible penetration levels of DG. Another increasingly important issue is the impact on transmission system voltages of DG reactive power demand. Here, a passive solution is proposed to reduce the impact on the transmission system voltages and overcome the distribution voltage rise barrier such that more DG can connect. The fixed power factors of the generators and the tap setting of the transmission transformer are determined by a linear programming formulation. The method is tested on a sample section of radial distribution network and on a model of the all island Irish transmission system illustrating that enhanced passive utilisation of voltage control resources can deliver many of the benefits of active management without any of the expense or perceived risk, while also satisfying the conflicting objectives of the transmission system operator. 2011-02-01T00:00:00Z http://hdl.handle.net/10197/3247 Impact of variable generation in generation resource planning models Shortt, Aonghus; O'Malley, Mark Long-term power system planning is beset by a trade-off between detail and scope: The chosen approach usually lies somewhere between modeling a great many generation portfolios coarsely and very few in a more detailed manner. This paper seeks to argue that the performance of generation portfolios is influenced by a sufficiently large number of variables, of varying uncertainties, such that the long-term investment problem can only be effectively tackled with very many runs of computationally light models that capture the most essential features of the problem. Taking a linear optimization program as the intended computational core, this paper describes two algorithms to build constraints for the linear program which capture many of the effects that are difficult or impossible to capture directly in non-chronological models, namely: unit starts, unit ramping, unit average output and adequate total system capacity. An application of these methods is also presented. Paper presented at the IEEE Power and Energy Society (PES) 2010 General Meeting, July 25-29 2010, Minneapolis, Minnesota 2010-07-01T00:00:00Z