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Municipal water supply consumes large quantities of electrical energy to move water from catchment areas to service reservoirs near centres of population. Pumping does not necessarily occur round the clock, but rather when necessary to uphold constraints relating to reservoir levels and system pressure. There is a degree of flexibility in the timing of pumping that makes it an excellent candidate for Demand Side Management, meaning that it can provide opportunities for improving power system operation and reducing electricity costs for the water utility. The extent of this flexibility depends on a number of factors. This study examines the optimisation of two water supply systems - the ‘Van Zyl’ benchmark system and a representation of the supply for the city of Belfast, Northern Ireland. The potential to employ intelligent operation of pumps to help bolster uptake of variable wind generation is assessed, as is quantification of the potential savings for a water utility. The results show significant potential savings for the water utility as well as a substantial increase in the utilisation of wind power.

The issues of climate change and dependence on fuel imports as well as a good local wind resource have led to a significant expansion of wind generation on the power system of Ireland in recent years, with further development planned. As it operates on a relatively small and isolated system, Irish wind generation must be carefully managed to mitigate its variable nature. This could lead to significant curtailment of wind power for system stability reasons, undermining the economic case for wind generation and reducing its effectiveness at displacing traditional, fossil-fired generation. This work quantifies the potential curtailment that might be seen on the future Irish and other power systems under several different scenarios, and presents Demand Side Management (DSM) as a tool to reduce curtailment. DSM of a water supply system is investigated to this end, as well as the inputs that would be necessary for such a system in order to benefit both the water system operator and the power system as a whole.

Many countries have set challenging wind power targets to achieve by 2020. This paper implements a realistic analysis of curtailment and constraint of wind energy at a nodal level using a unit commitment and economic dispatch model of the Irish Single Electricity Market in 2020. The key findings show that significant reduction in curtailment can be achieved when the system nonsynchronous penetration limit increases from 65% to 75%. For the period analyzed, this results in a decreased total generation cost and a reduction in the dispatch-down of wind. However, some nodes experience significant dispatch-down of wind, which can be in the order of 40%. This work illustrates the importance of implementing analysis at the nodal level for the purpose of power system planning.

The growth of wind power in some power systems is hampered by the system requirement for emergency reserve to cover loss of the biggest infeed. The study demonstrates that reserve provision from the wind sector itself has economic and operational benefits. A heuristic algorithm has been developed that can model the relevant aspects of emergency reserve provision in a system with both thermal and wind generations. The proposed algorithm is first validated by comparing its performance with established economic scheduling methods applied to a representative power system. The algorithm is then used to demonstrate the economic benefit of reserve provision from the wind sector. It is shown that such provision reduces wind energy curtailment and thermal unit ramping. Finally, it is shown that a wind sector capable of providing emergency reserve can expand economically beyond the capacity limit that would otherwise apply.

This paper presents a study on the implementation of Real-Time Pricing (RTP) based Demand Side Management (DSM) of water pumping at a clean water pumping station in Northern Ireland, with the intention of minimising electricity costs and maximising the usage of electricity from wind generation. A Genetic Algorithm (GA) was used to create pumping schedules based on system constraints and electricity tariff scenarios. Implementation of this method would allow the water network operator to make significant savings on electricity costs while also helping to mitigate the variability of wind generation.

This paper outlines the use of phasor measurement unit (PMU) records to validate models of fixed speed induction generator (FSIG)-based wind farms during frequency transients. Wind turbine manufacturers usually create their own proprietary models which they can supply to power system utilities for stability studies, subject to confidentiality agreements. However, it is desirable to confirm the accuracy of supplied models with measurements from the particular installation, in order to assess their validity under real field conditions. This is prudent due to possible changes in control algorithms and design retrofits, not accurately reflected or omitted in the supplied model. One important aspect of such models, especially for smaller power systems with limited inertia, is their accuracy during system frequency transients. This paper, therefore, assesses the accuracy of FSIG models with regard to frequency stability, and hence validates a subset of the model dynamics. Such models can then be used with confidence to assess wider system stability implications. The measured and simulated response of a wind farm using doubly fed induction generator (DFIG) technology is also assessed.

The increased availability of wind power is beginning to cause utilities problems as engineers attempt to synchronise the power grid. Utilities have tended to ignore the operational aspects of wind power until there are commercial pressures to take positive action. The nature of these pressures may be understood by considering the classic problem of unit commitment.

This paper presents a study on the implementation of Demand Side Management (DSM) of electricity use at one clean water pumping station in Northern Ireland and the application of DSM to public water supply with the intention of maximising wind power production. This approach will lead to reductions in wind curtailment and improvements in system stability. It will also allow signicant savings to be made on electricity costs for the water network.

This paper reviews the present purpose and functioning of grid codes for the proper operation of ‘national’ power networks. Now that embedded generation, including especially windfarms, may have total capacities large enough to compare with previous central generating plant, the grid codes are being changed to accommodate such generation. Modern wind turbines need to operate under new and challenging constraints that require the introduction of both new technology and sympathetic grid regimes. The most important characteristics affecting both the grid and the turbines are examined. It is concluded that modern wind turbines can generally be designed to support the maintenance of grid supply, frequency and voltage more effectively than present central plant. However, the manner in which that is achieved needs to be different in many respects from current codes that were developed around the characteristics of central and conventional plant. Indications of the necessary changes in grid codes are given.

The paper simulates the potential impact of significant wind power capacity on key operational aspects of a medium-sized grid-power system, viz. generator loading levels, system reserve availability and generator ramping requirements. The measured data, from Northern Ireland, consist of three years of 1/2 hourly metered records of (i) total energy generation and (ii) five wind farms, each of 5 MW capacity. These wind power data were scaled-up to represent a 10% annual energy contribution, taking account of diversity on the specific variability of total wind power output. The wind power generation reduced the system non-wind peak-generation. This reduction equalled 20% of the installed wind power capacity. There was also a reduction in the minimum non-wind generation, which equalled 43% of the wind power capacity. The analysis also showed that the spinning-reserve requirement depended on the accuracy of forecasting wind power ahead of scheduling, i.e. on the operational mode. When wind power was predicted accurately, (i) it was possible to reduce non-wind generation without over-commitment, but, (ii) the spinning-reserve non-wind conventional generation would usually have to be increased by 25% of the wind power capacity, unless quick-start gas generation was available. However, with unpredicted wind power generation, (i) despite reductions in non-wind generation, there was frequent over-commitment of conventional generation, but (ii) usually the spinning-reserve margin could be reduced by 10% of the wind power capacity with the same degree of risk. Finally, it was shown that wind power generation did not significantly increase the ramping duty on the system. For accurately predicted and unpredicted wind power the increases were only 4% and 5% respectively.

In this Grid Code the common rules for all generators are set down in the generation section of the Grid Code Connection Conditions. There are then a number of Schedules with requirements for particular types of generators. Only the Schedule for wind turbine generators is included here. WFPS refers to a wind farm power station.

Wind power is a clean and commercially competitive renewable energy technology that affords many utilities the opportunity to diversify and reduce their dependence on fossil fuels. However, the wind is also an intermittent energy source. Hence, many small and isolated utilities are concerned that, as the number and capacity of wind power plants increases, the resulting fluctuations in wind power output will impose excessive load following duty on their conventional units, leading to grid frequency control problems. This paper investigates the potential impact of wind energy development on the load following capability of a representative medium-sized, (2000 MW) thermal power system. Recorded system demand and wind power production data from the Northern Ireland system are statistically analysed, and the impact of expanded wind farm operation on net wind power and system demand fluctuations modelled and predicted for various time-scales of interest. The results demonstrate that the magnitudes of power output fluctuations from well-dispersed wind farms are small compared to system demand variations. Consequently, wind power expansion will not impose significant additional load following duty on the power system. Statistical analysis of net system demand and scaled wind farm time series data empirically verifies the validity of these findings.

Guyanas dependence upon imported petroleum fuels can only be offset by the sustained exploitation of its indigenous resources. With its populated coastlands exposed to the northeast trade winds and a history of small-scale wind energy utilisation wind is one such potential energy source. In this study, the coastal wind regime is analysed and historical data from a coastal weather station are used to estimate the potential for wind generation. It is found that a hybrid Weibull probability density function best describes the annual wind speed frequency distribution at the reference height of 10.67 m. With an annual mean wind speed of 5.8 m⧸s, an energy pattern factor of 1.41, and an annual average power density of 159 W⧸m2, this distribution represents a class-3 wind resource, suitable for most wind turbine applications. Site analysis and observed trends in coastal wind availability suggest the strong likelihood of a greater wind resource in more open locations. In view of its apparent potential for wind farm operation, a comprehensive, wind resource assessment programme is recommended for the Guyana coastlands.

This paper focuses on the use of flexible loads for providing emergency reserve to manage wind variability for a weakly interconnected power system. Ramping restrictions and starting costs of existing reserve facilities prompt research work on reserve from load. Flexible loads can be switched off quickly during under-frequency transients to maintain stable frequency and operation of the power system. Controlled heat pumps could be very helpful for providing a quickly available system reserve resource for regulating system frequency and hence system security and reliability. Different scenarios have been used to include the reserve from load and these scenarios have been used to schedule the Irish power system using the WILMAR planning tool for the year 2020. Considering a likely correlation of wind power expansion in both Irish and GB systems, the system operation cost, capacity factors of different technologies and the number of start-ups have been compared for reserve scenarios with and without an interconnection to the GB System. Finally, the reserve from flexible loads has been used to replace equivalent open-cycle gas turbine (OCGT) capacities and the results are compared for the defined scenarios.

This paper examines the growing issue of voltage management of medium-voltage (MV) distribution networks. These networks, especially in rural areas, often host a growing capacity of renewable generation, in particular wind turbine generators (WTGs). Wind generation in general causes voltage to rise. Such are the exacting voltage control requirements that distribution networks are vulnerable to the variability of wind generation. The paper presents a rigorous procedure for managing the network's voltage profile by adjusting WTG reactive compensation. The simplicity of the method renders it suitable for on-line use. Simulation studies show how the proposed voltage control scheme keeps voltage within limits in cases where strict adherence to most distribution codes would experience unacceptable voltage excursions. Finally, it will be shown that the approach has the potential to reduce losses. The paper also considers the limits on MV renewable generation imposed by grid reactive power requirements.

The paper is concerned with the challenges posed by the connection of wind turbine generators at a distribution voltage such as 11 kV, The capacity that can be connected within normal Distribution Code and operational limits is examined for a representative 11-kV rural feeder. The contrasting cases of concentrated and distributed generation are considered. It has been found that a modest reduction in power factor at higher loads, coupled with modified control of substation voltage, permits at least a doubling of the connected capacity. The reduced power factor at higher generation results in an increase in losses. However, it is shown that connecting the surplus power factor correction capacitance at times of heavy demand can recoup about half of the extra losses. It is also shown how the transients resulting from capacitor switching may be mitigated. (6 pages)

The synergy between electrically heated buildings and wind power generation is analyzed in this paper, with a view to providing lower cost heating and a demand side management resource that will facilitate the growth of renewable generation. The paper begins by demonstrating the relationship between electricity price and wind generation based upon recent market data from Ireland. Thermal parameters from a typical house in Northern Ireland are then used to model such a building's heat loss and thermal storage, and subsequently quantify the electrical energy consumed for heating by means of an air-source heat pump. A novel heating regime is then proposed which takes advantage of the building's thermal storage and the real-time market price of electricity, in order to lower costs. The simulations show that the proposed method can reduce the wholesale cost of heating by 10%, while maintaining a comfortable temperature range inside the building. It is also shown that the proposed method increases the correlation of heat load demand with wind power generation, a useful market mechanism for wind farm developers.

Governments in many countries including UK & Ireland are incentivising a higher percentage of electric power from renewable sources. In many places achieving this objective is heavily dependent on wind power. Historically, networks developed to serve load and are weak in windy areas. Network development requires permissions and therefore takes many years. This paper explores equipment and analysis to develop a set of line up-rating characteristics linked to the output of wind farms. The system and analysis is to provide an interim measure to enable power planners to connect more renewable energy sources while permission for new lines is being obtained. The equipment involves line mounted current and conductor surface temperature transducers and weather stations arranged regularly along the route. The information is transmitted by GPRS to a Web server where preliminary analysis presents information derived from the data. Further validation and analysis is carried out by downloading the raw data from the remote server. At the time of writing the paper the physical works are complete and validation/analysis is underway.

Wind power generation has expanded rapidly in the past two decades and supplies 20% of Denmarkpsilas electricity, and 5 - 7% in Germany, Spain and Ireland. It is likely that Ireland will be the first of these countries to reach the 10% level, probably by 2010. The Irish grid does not have the benefit of strong interconnection with neighbouring grids, as is the case with Denmark. If wind power is to push past the 10% level in Ireland, new system operational strategies will be needed. This paper describes a potential application for controllable domestic heat loads, and flexible distributed generation in power systems with significant capacities of uncertain wind generation. The paper demonstrates the prioritisation of these two balancing resources, the first derived from the electrical heat load component of system demand, the second derived from distributed diesel generation. The methods described can be effectively used to help match demand with generation during times of wind forecast errors.

An ensemble wind generation forecasting technique is described in this paper, based on a fusion of publicly available wind forecasts, persistence hold techniques and statistical methods. The forecasting method is applied to the Northern Irish power system where increasing capacity of installed wind generation makes forecast profiles an essential tool. The analysis is based on 6 months of wind generation and wind forecast data from the year 2006. The analysis incorporates the use of centrally controlled distributed diesel generation to cater for instances when the forecast wind generation is over-predicted and a shortfall exists. Power system scheduling software is used to simulate thermal plant operation with and without the described wind forecast. The work highlights the improvements in system efficiency and reduced fuel costs that are possible through application of a basic forecasting technique when combined with flexible distributed generation.

The impact of power fluctuations arising from fixed-speed wind turbines on the magnitude and frequency of inter-area oscillations has been investigated. The authors introduced data acquisition equipment to record the power flow on the interconnector between the Northern Ireland and Republic of Ireland systems. Through monitoring the interconnector oscillation using a fast Fourier transform, it was possible to determine the magnitude and frequency of the inter-area oscillation between the two systems. The impact of tower shadow on the output power from a wind farm was analysed using data recorded on site. A case study investigates the effect on the system of the removal of a large fixed-speed wind farm. Conclusions are drawn on the impact that conventional generation and the output from fixed-speed wind farms have on the stability of the Irish power system.

This paper considers a coordinated control strategy for adjacent FSIG and DFIG based wind farms whereby the reactive power output of the DFIG is prioritised over real power after a fault on the network, in order to boost the FSIG terminal voltage and improve its fault ride through capability. The issue of protection for a DFIG based wind turbine during network fault is also considered. It is seen that the large rotor currents can generally be ascribed to the small converter rating. Different protection arrangements for the converter are examined. The simulation results show that the stability margin of a FSIG can be significantly greater when there is extra reactive power compensation available from a DFIG in the vicinity.

Some form of regulation is a requirement in all electricity markets. The level of regulation is determined by the particular economic and political circumstances of each region. At a very minimum, the monopoly parts of the business, i.e. transmission and distribution, need to be regulated. Electricity markets are also subject to regulatory oversight. This is particularly important in markets where competition is in its infancy where, for example, an incumbent VIU still maintains a dominant position. Regulatory decisions can and do have very large financial consequences for the participants and poor regulation can lead to risks for participants. With large amounts of wind power, with its unique characteristics, being connected to electricity systems, there is a danger that regulators will fail to grasp the issues and make decisions that will stifle the development of the industry as a whole and wind power in particular. If the regulatory regime is too favourable to wind power, then it will thrive at the expense of the other parts of the industry, which will be damaging. If the regulator is too severe with wind power, then investment in the sector will suffer, and society will fail to benefit from the emissions reduction and security of supply potential of the technology. Regulators need to encourage innovation and to help the industry to seek out the most effective means of wind power integration.

While considerable progress has been made in wind power forecasting in the last decade or so, in terms of better understanding of the processes involved and higher accuracy of the forecasts, there is still plenty of scope for improvement. Clearly forecasts for the wind power production of whole regions or supply areas are more accurate than forecasts for particular wind farms due to the smoothing effect of geographic dispersion of wind power capacity. However, with the trend towards large wind farms, and particularly large offshore wind farms, there is a growing requirement for accurate forecasts for individual wind farms. There are considerable differences in the accuracy that can be achieved for wind power forecasts for wind farms located in very complex terrain compared to open flat terrain. Current research on meso scale modelling aims to address this problem. The development of offshore wind power also presents difficult challenges for wind power forecasting. The uncertainty attached to a forecast is a key concern, particularly when looking to the participation of wind power in electricity markets. The area of ensemble forecasting shows potential for further progress. The other area of interest will be the integration of wind power forecasting tools into the energy management systems of TSOs.

Most wind power capacity is connected to electricity supply networks, and this is likely to continue for the foreseeable future. The advantages of connection to a grid include: the ability to locate wind farms where the wind resource is plentiful, irrespective of demand; the ability of an interconnected grid to absorb variations in wind generation unrelated to overall demand variation; provision of excitation, enabling simple induction machines to be used as generators. These advantages are qualified by various limitations of the power supply system, and Chapters 4 and 5 will consider how the resulting problems can be overcome. However, the fact remains that grid connection has provided a major impetus to the growth of wind energy. Hence it is important to understand the fundamentals of electrical power engineering presented in this chapter. The chapter will start with the basic principles of electrical engineering. The discussion will lead naturally to the transformer, found in all wind farms as well as throughout power supply systems. We then consider alternating current (AC) systems, with particular emphasis on active and reactive power and the use of phasors. Power supply systems are then considered. The chapter will close with an introduction to AC power transmission.

This chapter first examines how conventional generating units can be scheduled and operated to cope with variations in the demand under both normal and emergency conditions (Section 5.2). The inclusion of wind generation in this task creates potential problems, as the power output of individual turbines is subject to time varying weather patterns. Section 5.3 begins by presenting a status report on how various countries are addressing the challenges (Section 5.3.1). Then, taking the island of Ireland as an example, the variability of wind output on different geographical scales and operational timeframes is examined in detail (Section 5.3.2). Various key problems of wind power integration on a significant scale, with some current solutions, are discussed in Sections 5.3.3-5.3.8. Wind forecasting is a useful tool, in this respect, and its potential role is discussed briefly here before being examined in detail in Chapter 6. Finally, a number of alternative storage solutions, which can play a role in maintaining the desired energy balance, are examined in Section 5.4, facilitating further wind farm expansion. This section includes a discussion of how demand-side management can provide some of the benefits of energy storage at minimal cost.

This chapter examines the effect of wind generation on the transmission and distribution network to which it is connected. Topics include control of voltage and power flows, the quality of supply and the protection of plant and equipment. The principles underlying network development in the face of increasing wind generation are reviewed. The perspective is that of a network operator sympathetic to wind power development. It will be seen that wind power capacity may exceed strict technical limits, provided wind power operators are prepared to accept occasional energy curtailment. Achievement of this ideal balance will require enlightened negotiation between the two parties. Appendix 2 is an extract from a current and practical grid code. The language is legalistic, as in most grid codes, but it serves to show how network operators (referred to as the Transmission System Operator (TSO) in Appendix 2) express many of the issues discussed here.

The main purpose here is to explain the technology in common use for large-scale wind power generation. The evolution of turbine design is first of all placed in its historical context. The current design choices facing the industry are then considered. A simple analysis of the basic process of wind energy extraction is presented, leading to a discussion of the critical area of power regulation. It will be seen that the options here depend on whether fixed or variable-speed technology is adopted. The description of fixed-speed wind turbine technology includes a review of relevant induction machine theory. The induction (or asynchronous) machine is a key component of fixed-speed wind generators, as well as forming the basis for partial variable-speed designs. This section considers some of the shortcomings of the fixed-speed designs which dominated the industry's initial growth surge. The final section of the chapter reviews the arguments that have led to the growing dominance of variable-speed technology The section includes a detailed treatment of partial variable-speed (doubly fed induction generator [DFIG]) and full variable-speed wind turbine generator configurations.

The impact of power fluctuations arising from fixed-speed wind turbines on the magnitude and frequency of inter-area oscillations was investigated. The authors used data acquisition equipment to record the power flow on the interconnector between the Northern Ireland and Republic of Ireland systems. By monitoring the interconnector oscillation using a fast fourier transform, it was possible to determine the magnitude and frequency of the inter-area oscillation between the Northern Ireland Electricity system and that of the Electricity Supply Board. Analysis was preformed to determine the relationship (if any) between the inter-area oscillation and the observed wind power generation at the corresponding time. Subsequently, regression analysis was introduced to model this relationship between the FFT output and the wind power generation. The effect of conventional generators on the magnitude and frequency of the inter-area oscillation was also considered.

A major problem with wind power is that it is intermittent. Even if it were predictable, the problem of matching generation to demand is difficult. Storage is sometimes advocated, but this tends to be very expensive. The paper examines the main conventional solutions to the intermittency problem - provision of extra reserve generation to compensate for unexpected wind power lulls, and increased interconnection to facilitate support from, and for, neighbouring utilities. The paper then considers a third avenue - use of wind energy to supply heating load. It is feasible to incorporate low-cost energy storage as part of a wind-powered heating package for domestic consumers. It is argued that coordination of the dispersed storage can help solve the wind intermittency problem.

The inertia of fixed-speed wind turbine generators (WTGs) helps to mitigate under-frequency transients, promotes fault ride-through and damps inter-area oscillations. It is therefore important to quantify this inertia. The authors use measured wind farm responses during under-frequency transients to provide this information. They discuss the extent of the data and the criteria used to select certain events for further analysis. The estimation of WTG inertia is based on a induction generator model. The basis of the model will be described. The manner in which the model is applied to estimate the inertia from the measured data is then explained. Finally, the implications of the results for power system operation are assessed.

Full exploitation of the environmental and financial benefits of wind-generated energy in a power system requires prediction of the wind energy profile well in advance of delivery. On the basis of forecast profile and associated confidence, wind energy can be included in the unit commitment/economic dispatch procedure, resulting in near-optimal commitment and loading of thermal plant, thereby saving fuel. A wind forecasting methodology, which closely resembles a commercial wind forecasting package, is adopted to illustrate the possible instances of significant over-forecasting, although rare, and exposure of the system to substantial risk. It is shown that the cost of additional spinning reserve necessary for such cases is prohibitive, and a fast, flexible generation, such as diesel gen-sets are considered as a superior mechanism to balance any such shortfalls. The Northern Ireland power system is used as a case study to demonstrate the environmental and financial benefits of using distributed diesel generation in the manner described above. The study is based on a six-month period system data, and is applied to various future scenarios of the installed wind. It is shown that the methodology can mitigate many of the problems associated with large-scale wind penetration on a synchronously islanded system.

Remotely connected wind farms can have a significant impact on voltages, load demand and power losses in radial distribution networks. Quantification of these effects is important in determining the true value of wind energy and requires detailed simulations of integrated network behaviour over an extended period of time. The steady state behaviour of commercial and residential radial distribution feeders with remotely connected wind turbines has been investigated using a recursive, loadflow-based simulation algorithm and time series data from a known system. The results of annual simulations reveal that large wind farm capacities can be freely operated in remote locations without violation of voltage limits and with a net reduction in feeder energy consumption. With automatic control of real and reactive power flows from the wind farm, connected capacity can be significantly expanded before operation becomes infeasible.

The inherent variability and uncertainty of wind power generation is a major issue for countries attempting to harness large quantities of wind-based renewable energy. Such properties of wind make optimal balancing of demand and generation a much more complex task. Clearly the flexibility of thermal plant in the electrical power system is of key importance, especially in smaller systems with high penetrations of wind power, as is the role of interconnectors with neighbouring countries. This paper examines the power system of Ireland as a test case for systems with high wind penetrations and limited interconnection to neighbouring countries, such that wind variability must be managed using indigenous methods. The analysis highlights problems other power systems will encounter as they in turn reach high penetrations of wind generation.

Wind power generator and total capacity has increased dramatically in the last 10 years. Most generators now being installed use doubly-fed induction machines (DFIGs). These allow active and reactive power control through the rotor side converter. Therefore today's wind turbines have a significant impact on the power system. To ensure power quality, several utilities have introduced special grid connection codes for wind farm developers. The requirements range from reactive power control, frequency response and, last but not least, fault ride-through. All these requirements, especially fault ride-through, are a challenge for wind turbine producers. New control strategies and hardware are needed which utilize the flexibility provided by the DFIG converters. This paper outlines the proposed grid codes. It then describes a detailed DFIG model and control strategy. The performance of the new control through severe fault conditions is demonstrated.