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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.

Grid operators and electricity retailers in Ireland manage peak demand, power system balancing and grid congestion by offering relevant incentives to consumers to reduce or shift their load. The need for active consumers in the home using smart appliances has never been greater, due to increased variable renewable generation and grid constraints. In this paper an aggregated model of a single compressor fridge-freezer population is developed. A price control strategy is examined to quantify and value demand response savings during a representative winter and summer week for Ireland in 2020. The results show an average reduction in fridge-freezer operating cost of 8.2% during winter and significantly lower during summer in Ireland. A peak reduction of at least 68% of the average winter refrigeration load is achieved consistently during the week analysed using a staggering control mode. An analysis of the current ancillary service payments confirms that these are insufficient to ensure widespread uptake by the small consumer, and new mechanisms need to be developed to make becoming an active consumer attractive. Demand response is proposed as a new ancillary service called ramping capability, as the need for this service will increase with more renewable energy penetration on the power system.

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 examines the ability of the doubly fed induction generator (DFIG) to deliver multiple reactive power objectives during variable wind conditions. The reactive power requirement is decomposed based on various control objectives (e.g. power factor control, voltage control, loss minimisation, and flicker mitigation) defined around different time frames (i.e. seconds, minutes, and hourly), and the control reference is generated by aggregating the individual reactive power requirement for each control strategy. A novel coordinated controller is implemented for the rotor-side converter and the grid-side converter considering their capability curves and illustrating that it can effectively utilise the aggregated DFIG reactive power capability for system performance enhancement. The performance of the multi-objective strategy is examined for a range of wind and network conditions, and it is shown that for the majority of the scenarios, more than 92% of the main control objective can be achieved while introducing the integrated flicker control scheme with the main reactive power control scheme. Therefore, optimal control coordination across the different control strategies can maximise the availability of ancillary services from DFIG-based wind farms without additional dynamic reactive power devices being installed in power networks

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.

Most wind farms currently being installed are based upon doubly fed induction generator (DFIG) or direct-drive synchronous generator (DDSG) technology. Given that one of the impacts of introducing distributed generation is an alteration of steady-state power flows and voltages, both technologies are capable of providing local voltage support. Wind farms may, therefore, be included in optimal power flow (OPF) calculations to minimise fuel cost and/or network losses. The IEEE 30-bus system is considered as a case study, comparing fixed-speed induction generator (FSIG) requirements with DFIG capability. Results are presented for a range of DFIG capability modes, at varying system load and wind farm penetration levels. A significant reduction in losses can be achieved by suitable co-ordination of DFIG reactive power import/export, operating within typical grid code specifications. It is shown that the dynamic variability of reactive power requirements is readily accommodated by the power system. Finally, implementation options for the scheme and incentivising strategies are considered.

The paper presents a multiple-input single-output fuzzy logic governor algorithm that can be used to improve the transient response of a diesel generating set, when supplying an islanded load. The proposed governor uses the traditional speed input in addition to voltage and power factor to modify the fueling requirements during various load disturbances. The use of fuzzy logic control allows the use of proportional-integral-derivative (PID) type structures that can provide variable gain strategies to account for nonlinearities in the system. Fuzzy logic also provides a means of processing other input information by linguistic reasoning and a logical control output to aid the governor action during transient disturbance. The test results were obtained using a 50 kVA naturally aspirated diesel generator testing facility. Both real and reactive load tests were conducted. The complex load test results demonstrate that, by using additional inputs to the governor algorithm, enhanced generator transient speed recovery response can be obtained.

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.

The need for fast response demand side participation (DSP) has never been greater due to increased wind power penetration. White domestic goods suppliers are currently developing a ‘smart’ chip for a range of domestic appliances (e.g. refrigeration units, tumble dryers and storage heaters) to support the home as a DSP unit in future power systems. This paper presents an aggregated population-based model of a single compressor fridge-freezer. Two scenarios (i.e. energy efficiency class and size) for valley filling and peak shaving are examined to quantify and value DSP savings in 2020. The analysis shows potential peak reductions of 40 MW to 55 MW are achievable in the Single wholesale Electricity Market of Ireland (i.e. the test system), and valley demand increases of up to 30 MW. The study also shows the importance of the control strategy start time and the staggering of the devices to obtain the desired filling or shaving effect.

This paper is concerned with the detailed implementation of real-time fuzzy logic speed control for a standby diesel-generating set. The implementation platform is that of the Mathworks xPC Target. This rapid prototyping scheme permits the automatic cross-compiling of the nonreal-time Simulink control system model into real-time C code, which is executable on the xPC target PC. The digital governor xPC target hardware consists of a desktop PC with a National Instrument Input/Ouput card and a Softing Controller Area Network Card. The paper details the fuzzy control model and the methods with which to communicate with the engine control module. Tests were conducted on a 50-kVA diesel-generating set. The results show that the fuzzy controller is superior to the variable gain PID-type governor used by the conventional engine control module.

Summary form only given. Tidal stream generation is a form of renewable energy that is predictable but variable in nature. The paper initially identifies the tidal resource around Ireland, utilizing the most appropriate and developed tidal energy technology, thus providing a potential magnitude and output profile. Methods of deployment and control, including the down rating of the generator relative to turbine size and operational output reduction, are suggested to reduce capital cost, increase the capacity factor and reduce the impact on the grid system. The combination of the potential resource and the application of control methods provide the basis to study the effect on the grid system in terms of ramp rate and the demand profile. The same inputs also provide the ability to analyze generator characteristics such as the capacity credit.

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.

Akmal, M., Fox, B., Morrow, J. D., & Littler, T. (2014). Impact of heat pump load on distribution networks. IET Generation, Transmission & Distribution, 8(12), 2065-2073., Heat pumps can provide domestic heating at a cost that is competitive with oil heating in particular. If the electricity supply contains a significant amount of renewable generation, a move from fossil fuel heating to heat pumps can reduce greenhouse gas emissions. The inherent thermal storage of heat pump installations can also provide the electricity supplier with valuable flexibility. The increase in heat pump installations in the UK and Europe in the last few years poses a challenge for low-voltage networks, because of the use of induction motors to drive the pump compressors. The induction motor load tends to depress voltage, especially on starting. The study includes experimental results, dynamic load modelling, comparison of experimental results and simulation results for various levels of heat pump deployment. The simulations are based on a generic test network designed to capture the main characteristics of UK distribution system practice. The simulations employ DIgSlILENT Power Factory to facilitate dynamic simulations that focus on starting current, voltage variations, active power, reactive power and switching transients.

This paper describes a fridge-freezer smart load model, which responds to external signals from the wholesale electricity market to support grid operations while switching the fridge-freezer on and off to maintain optimum operations for the owner. The key parameters of the model are the appliance dimensions, thermal mass, the fridge and freezer thermal time constants and the compressor power consumption. The model demonstrates that control strategies help to minimise load at times when the grid is under stress from high demand, and shift some load to a lower wholesale price or when there is excess renewable power. Three control strategies are proposed, based on peak shaving and valley filling, price signals and wind availability.

The paper presents a methodology for managing a network's voltage profile by dispatching grid-connected distributed generation (DG). The coordinated voltage control algorithm has two main stages for controlling network voltages. Firstly, it avails of any available network reactive power assets and reactive power available from DG which is dispatched to coincide with network needs. If insufficent reactive power is available from the DG units their active power may be curtailed to free up reactive power to ensure voltages are within the desired range. The paper demonstrates that the sensitivity based approach can maintain voltages within the desired range and has the potential to reduce network losses, increase network capacity to accommodate DG and to reduce the distribution network's dependence on the transmission network for reactive power.

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.

Flexible alternating current transmission system (FACTS) devices are expensive, and it is necessary to ensure that their functionality is required before specifying them. They perform four basic functions, which can be combined in different devices: 1. Power transfer between electrically separated systems 2. Active power management 3. Reactive power management 4. Waveform quality management.Active power management devices (for example phase shifters, static synchronous series compensators and unified power flow controllers) that are less relevant to wind technology, either internally or in connection terms, will not be discussed here. Current source converters for high-voltage direct current (HVDC) are dealt with for completeness, although it is likely that most large wind farms would be connected by voltage source converter technology, and doubly fed induction generators (DFIGs) apply this technology in their rotor circuits. Synchronous connection by lines and cables makes two electrical systems behave as one. This clearly is inappropriate if the frequencies are different or one system has a stability or fault level problem that would be exacerbated by connection with another source. In these circumstances the systems may be maintained as separate entities through a converter/inverter DC path. In each of the other applications, traditional technology exists but performs its function slowly or within a narrow range. It is the need for rapid action in controlling active and reactive power and the need to manage a wide range of waveform distortion problems that requires the application of FACTS devices.

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.

Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by combining data from observatories located in both the northern and southern hemispheres. To this end, a joint analysis using data recorded at the Telescope Array and the Pierre Auger Observatory above 1019 eV is presented in this work. The resulting multipolar expansion of the flux of cosmic rays allows us to perform a series of anisotropy searches, and in particular to report on the angular power spectrum of cosmic rays above 1019 eV. No significant deviation from isotropic expectations is found throughout the analyses performed. Upper limits on the amplitudes of the dipole and quadrupole moments are derived as a function of the direction in the sky, varying between 7% and 13% for the dipole and between 7% and 10% for a symmetric quadrupole., Facultad de Ciencias Exactas

This study characterizes the domestic loads suitable to participate in the load participation scheme to make the power system more carbon and economically efficient by shifting the electricity demand profile towards periods when there is plentiful renewable in-feed. A series of experiments have been performed on a common fridge-freezer, both completely empty and half full. The results presented are ambient temperature, temperature inside the fridge, temperature inside the drawer of the fridge, temperature inside the freezer, thermal time constants, power consumption and electric energy consumed. The thermal time constants obtained clearly demonstrate the potential of such refrigeration load for Smart Customer Load Participation.

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.

This paper is concerned with the voltage and reactive power issues surrounding the connection of Distributed Generation (DG) on the low-voltage (LV) distribution network. The presented system-wide voltage control algorithm consists of three stages. Firstly available reactive power reserves are utilized. Then, if required, DG active power output is curtailed. Finally, curtailment of non-critical site demand is considered. The control methodology is tested on a variant of the 13-bus IEEE Node Radial Distribution Test Feeder. The presented control algorithm demonstrated that the distribution system operator (DSO) can maintain voltage levels within a desired statutory range by dispatching reactive power from DG or network devices. The practical application of the control strategy is discussed.

A fast decoupled load flow for transient stability studies is developed. A decoupled differential generator model is derived using the Newton-Raphson technique and trigonmetrical transformations of voltage and angle variables. A voltage/angle-invariant modified Jacobian is defined and the need for Jacobian refactorizations minimized. Composite variables, representing angle corrections multiplied by voltages, are used for the active power flow modelling in conditions with large voltage variation. The voltage/angle invariant modified Jacobian and the decoupled load flow equations are also applied to short circuit calculations. An 18-bus, 5-generator test system is used to illustrate the proposed algorithm.

This paper investigates a knowledge-based feedback controller designed to enhance the quality of control of generator speed and power system frequency. The discrete supplementary digital control signal is implemented on the turbogenerator speed control loop, introducing intelligent adaptive acceleration feedback. Employing this type of control results in diminishing of over- and under-frequency deviations and reduced generator and load shedding. >

This paper describes the results of an investigation concerning the on-line prediction and enhancement of load relief. The effects of voltage fluctuation, system voltage profile control and generator voltage adjustment on load relief and load shedding operations during under-frequency transients are studied. The technique promoted in the paper may be used to reduce system spinning reserve or prospective load shedding. >

Heat pumps are vitally important for achieving low carbon and renewable energy targets. There is a rapid increase in heat pump installations in the UK and Europe in the last few years for their supporting role towards green energy and demand-side management. The increase in heat pump installation prompts research work on the impact of high penetration of heat pumps on the low voltage network. This paper includes experimental results, dynamic load modelling, comparison of experimental and simulation results for the model of the heat pump, modelling a test network and its simulation in DIgSILENT. The UK generic distribution network, which represents an urban distribution network, has been used for system simulation. s. Parameters such as starting current, voltage variations, active power, reactive power at various switching instances, impact of single-phase loading and the additional loading of the network are examined.

Due to the deregulation of the power supply industry and the continuing need for network expansion, there is pressure to maximize utilization of the existing transmission and distribution networks. Compared to the traditional static line rating, a dynamic line rating provides a more accurate methodology to determine the ampacity of the overhead line in real time. Taking the wind cooling effect into account allows extra power to be accommodated. Line-rating methodologies developed based on IEEE and CIGRE standards are widely employed for dynamic line ratings. However, there are a number of parameters that need to be chosen for each line which can lead to errors in the temperature/ampacity prediction. In comparison, the statistical technique, partial least squares (PLS) regression, only requires the monitored data to be collected. The model coefficients are determined by processing the data sets over a period, such as one year. In this paper, both physical (CIGRE) and statistical (PLS) models are analyzed using the data collected from field testing, and the comparisons of the two models are also demonstrated.

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)

This paper investigates the performance characteristics of rapeseed methyl ester, EN 14214 biodiesel, when used for electrical generation in compression ignition engines. The work was inspired by the need to replace fossil diesel fuel with a sustainable low carbon alternative while maintaining generator performance, power quality and compliance with ISO 8528-5. A 50 kVA Perkins diesel engine generator was used to assess the impact of biodiesel with particular regard to gen-set fuel consumption, load acceptance and associated standards. Tests were performed on the diesel gen-set for islanded and grid-connected modes of operation, hence both steady-state and transient performance were fully explored. Performance comparisons were made with conventional fossil diesel fuel, revealing minimal technical barriers for electrical generation from this sustainable, carbon benign fuel.

This paper presents a flicker mitigation scheme for the doubly-fed induction generator (DFIG) during variable wind conditions. The flicker mitigation strategy was developed based on the distribution line X/R ratio and the active power deviation from the average active power during variable wind conditions. Flicker emission was analyzed using a flicker meter based on the IEC standards. Both short-term and long-term flicker severities were analyzed during the time period of study. The flicker mitigation strategy was evaluated under different system conditions such as X/R ratio, distribution line length, short-circuit capacity (SCC), and wind variability. It is shown that the proposed control scheme mitigates flicker severity with different X/R ratios, distribution line lengths and different wind conditions. However, the proposed strategy is less effective with relatively low SCCs at the point of grid connection, due to large fluctuations of the voltage at the point of grid connection.

This paper investigates the performance characteristics of rapeseed methyl ester, EN 14214 biodiesel, when used for electrical generation in compression ignition engines. The work was inspired by the need to replace fossil diesel fuel with a sustainable low carbon alternative while maintaining generator performance, power quality, and compliance with ISO 8528-5. A 50-kVA Perkins diesel engine generator was used to assess the impact of biodiesel with particular regard to gen-set fuel consumption, load acceptance, and associated standards. Tests were performed on the diesel gen-set for islanded and grid-connected modes of operation, hence both steady-state and transient performance were fully explored. Performance comparisons were made with conventional fossil diesel fuel, revealing minimal technical barriers for electrical generation from this sustainable, carbon benign fuel. Recommendations for improved transient performance are proposed and validated through tests.

The paper considers the behaviour of the rotor current of a DFIG during a fault on the network. It is seen that a large disturbance of the stator voltage will cause high transient rotor currents which trigger the crowbar protection for the rotor side converter (RSC). Once the crowbar is applied it cannot be removed until its current reaches zero. During the period the crowbar is applied, the machine behaves as a conventional FSIG, losing control of the active and reactive power. Therefore the time taken for the crowbar current to reach zero is crucial as it determines when the RSC can regain power control and how soon the AC voltage can recover. It is seen that the crowbar current can take a long time to decrease to zero and that this has a significant impact on the voltage recovery after fault. The larger the crowbar resistor and the further the generator is from synchronous speed, the shorter the crowbar current transient is. Power and energy dissipation through the crowbar resistor are also considered, and it is observed that the power varies in accordance with the maximum power transfer theorem. The detailed impact of the timings of crowbar removal and RSC reactivation on system voltage recovery is also investigated. It is seen that reactive power control during fault clearance can assist AC voltage recovery.

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.

The role of roughening and functionalization processes involved in modifying the wettability of poly(epsilon-caprolactone) (PCL) after treatment by an atmospheric pressure glow discharge plasma is discussed. The change in the ratio of CO/C-O bonds is a significant factor influencing the wettability of PCL. As the contact angle decreases, the level of CO bonds tends to rise. Surface roughness alterations are the driving force for lasting increases in wettability, while the surface functional species are shorter lived. We can approximate from ageing that the increase in wettability for PCL after plasma treatment is 55-60% due to roughening and 40-45% due to surface functionalization for the plasma device investigated.

This paper describes the control and operation of an HVDC system comprising a line-commuted converter (LCC) HVDC and a STATCOM for connecting offshore wind farms based on DFIGs. During fault on the main grid, fast communications have previously been relied upon to make the wind farm aware of the condition and reduce its power output. Here, an alternative method is examined which enables automatic power balancing during fault. This is achieved through frequency modulation on the offshore network via the STATCOM. Several methods of fault detection using frequency threshold, rate of change of frequency (ROCOF) and rate of change of AC voltage (ROCOVac) are used to indicate when the wind farm power output should be reduced to achieve power balancing, and are compared with results using direct communications. PSCAD/EMTDC simulations show the effectiveness of the proposed control, which allows for faster fault identification. As a result the STATCOM DC over-voltage can be significantly reduced, requiring small DC capacitor, and tripping of the wind farm can be avoided.