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New Publications are available now online for this publication.
Please follow the links to view the publication.An economic model for power exchange of V2GS in parking lots
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0797
Each battery vehicle (V2G) can be charged from the power grid or return its stored energy back to the grid. The effect of a single V2G on the power grid is approximately an ignorable noise. Parking lots can cumulate hundreds of V2Gs in a way that their load/generation impact can influence the grid. This paper proposes a technical and economic model for managing the charging and discharging time of battery vehicles in a parking lot. This model is employed maximizes the parking lot profit, while satisfying vehicle owners. The Genetic Algorithm (GA) is used to set the charging & discharging time table of vehicles. Finally, profit fluctuations due to varying the V2G parameters are investigated. (4 pages)Optimal sizing of hybrid energy resources for electrifying distant rural areas of Iran
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0867
Mathematical models are presented for PVs, wind turbines, battery storages and diesel generators for optimal in a hybrid isolated system. The optimization model is formulated and a case study is run in a rural nonelectrified area of Iran. (4 pages)PV, battery storage and energy conversion system for meeting peak load in a substation
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0758
Out of firm (OOF) conditions at a distribution substations may last for several hours and it is quite common in a rapidly growing distribution system like the one at Kahramaa (Qatar). Dealing with such a condition is a big challenge for network planners. Combination of renewable, power electronics and advent of more efficient storage systems can give innovative solutions to similar challenges. This paper describes a methodology of using energy storage system, including photo voltaic and battery storage, to provide energy during the peak hours of the day to avoid N-1 violation of reliability criteria. The methodology would be implemented at a selected substation, and the implementation process is also outlined in the paper. The application is inline with Kahramaa strategic plans to comply with Qatar National Vision 2030. (4 pages)Development of dimensioning and allocation algorithms for different applications of battery storage units
http://dl-live.theiet.org/content/conferences/10.1049/cp.2012.0861
In scope of this paper, the question of how to optimally utilize, dimension and allocate a battery storage unit (BSU) has been briefly addressed. Based on a novel generic BSU model, three main application fields of BSU are explored: market arbitrage, renewable firming, and network support. Main obstacles of modelling and simulation are identified in the process, and practical solution and applicable examples are analyzed to address these topics. (4 pages)Generic modelling framework for economic analysis of battery systems
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0147
Deregulated electricity markets provide opportunities for Battery Systems (BS) to participate in energy arbitrage and ancillary services (regulation, operating reserves, contingency reserves, voltage regulation, power quality etc.)To evaluate the economic viability of BS with different business opportunities, a generic modelling framework is proposed to handle this task. This framework outlines a set of building blocks which are necessary for carrying out the economic analysis of various BS applications. Further, special focus is given on describing how to use the rainflow cycle counting algorithm for battery cycle life estimation, since the cycle life plays a central role in the economic analysis of BS. To illustrate the modelling framework, a case study using a Sodium Sulfur Battery (NAS) system with 5-minute regulating service is performed. The economic performances of two dispatch scenarios, a so called naive scenario and a risk-averse scenario, are evaluated in this case study. (6 pages)Design of an energy storage system in a multi machine power system
http://dl-live.theiet.org/content/conferences/10.1049/cp.2011.0207
In order to understand how an energy storage system (ESS) based stabilizer suppresses a power system inter-area oscillation in a multi-machine power system, this paper proposes a tie-line power oscillation related ESS linearized model. Based on the linearized model, a general conclusion is established to explain how and why the ESS based stabilizer to affect the damping of the inter-area power oscillation. And based on the model and the general conclusion, a new method is proposed to design the ESS stabilizer when it is realized by controlling the exchange of either active or reactive power between the ESS and the rest of the power system. The paper presents an example multi-machine power system installed with a battery energy storage system (BESS) based stabilizer. Results of eigensolutions computation and non-linear simulation demonstrate and confirm the effectiveness of the ESS based stabilizer designed by the proposed method in suppressing the inter-area power oscillation. (6 pages)Battery-supercapacitors mixed as electrical power buffers
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0124
In this paper, a battery-supercapacitor hybrid power system of electrical power buffers, which helps to improve a dynamic behaviour of power sources with diesel engines, is presented. The results of battery analyses are shown and it is emphasised that the combination of batteries and supercapacitors can minimise output mass and volume of power sources with diesel engine. The batteries facilitate extended high power supply and supercapacitors protect the batteries from the frequent high power peaks during battery discharging that significantly reduces battery lifetime. The values of benefits have been estimated for applying energy storage of many types of batteries. Paper gives brief outline the features of the experimental verification of batteries and discusses the basic topologies of dc-dc bi-directional converters. The scheme and detail of experimental workplace are shown in paper and tested using Agilent VEE. (6 pages)Single stage grid converters for battery energy storage
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0016
Integration of renewable energy systems in the power system network such as wind and solar is still a challenge in our days. Energy storage systems (ESS) can overcome the disadvantage of volatile generation of the renewable energy sources. This paper presents power converters for battery energy storage systems (BESS) which can interface medium-voltage batteries to the grid. Converter topologies comparison is performed in terms of efficiency, common mode voltage and redundancy for a 6kV series connected medium voltage batteries with a nominal power of 5MVA to act as a battery charger/discharger. (6 pages)Power electronics and energy management of hybrid power sources with supercapacitors
http://dl-live.theiet.org/content/conferences/10.1049/cp.2010.0116
Hybrid power sources with energetic buffer technology are based on supercapacitors with bi-directional dc-dc converters. This paper describes the application of bi-directional converters with Supercapacitors for remote area power hybrid sources using photovoltaic sources, Diesel Generator Sets and battery storage. One of the future trends in that area of power sources supercapacitors are introduced. The system of power electronic converter consists of ac-dc rectifier, dc-dc, dc-ac inverter, bi-directional converter and supercapacitor was set up and verified. This concept of power electronics is beneficial, compared with the un-centralized system without battery buffer, since higher dynamic behaviours can be achieved. Power management of hybrid power sources is also presented. (6 pages)High power RF capabilities at Loughborough University
http://dl-live.theiet.org/content/conferences/10.1049/cp.2009.0001
Members of the plasma and pulsed power group at Loughborough University are engaged in several experimental activities related to the generation of high power radio frequency radiation. The paper reviews some of the more important projects that have recently been successfully completed. (5 pages)Reliability assessment of distribution system with distributed generation based-on conditional value at risk
http://dl-live.theiet.org/content/conferences/10.1049/cp_20062056
Great changes are brought about to the traditional distribution system by distributed generation (DG) due to its characteristics, and conditional value at risk is introduced to evaluate the impacts including the uncertainty of the power source and the starting problem. Two models are set up according to the DG's operation strategy. Probabilistic results present the possible power shortfall at different confidence levels. (4 pages)Design consideration and operational experience of DC battery/charger system with automatic battery test in distribution substations
http://dl-live.theiet.org/content/conferences/10.1049/cp_20062165
The reliability of power system protection and control depend on the reliability of DC supply system. Traditionally, reliability of DC supply for power system protection is ensured by duplicate battery/charger systems with extensive maintenance efforts such as regular shallow/deep discharge tests. However, the resources necessary to implement such arrangement in distribution network will be tremendous. After careful consideration of the technical advantages and cost impact of alternative battery/charger arrangements, single 'maintenance free' battery bank and charger system was chosen for the new 22kV distribution network introduced in Hongkong electric. (5 pages)Feasibility study of battery energy storage system with power quality support in Malaysia
http://dl-live.theiet.org/content/conferences/10.1049/cp_20051055
The paper describes potential of battery energy storage system (BESS) in Malaysia focussing in particular the use of advanced sodium sulfur (NAS) battery. NAS-BESS is considered because of its special characteristics and capability that enables hybrid use of load levelling and power quality improvement. Various applications of BESS will be described together with case studies of potential benefits to utility and customers in Malaysia. Even though the use of energy storage system is not yet critical in Malaysia, this paper will attempt to present analysis and potential benefits of BESS applications for TNB and its large power users. (5 pages)A history of the use of internal combustion engine driven generating sets in the UK telecommunications network 1900-2000
http://dl-live.theiet.org/content/conferences/10.1049/cp_20010593
This paper gives an overview of the use of internal combustion engine driven generating sets providing power in the UK telecommunications network operated by the General Post Office (GPO), Post Office Telecommunications (POT) and British Telecom (BT) over the last one hundred years. The use of both fixed and mobile plant is included for both prime power and standby purposes. Town gas, petrol and compression ignition prime movers are also covered. The telecommunications services requiring power are identified, together with the dates when particular items first entered service.An advanced unified power flow controller (AUPFC) using energy storage
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000394
This paper describes several new topologies of an intelligent power compensation system utilizing energy storage to enhance power system performance and reliability. The system can also provide all the benefits associated with a unified power flow controller (UPFC). In one single device, the advanced unified power flow controller (AUPFC) can provide: (i) fast control of real and reactive power along a transmission corridor; (ii) phase angle control; (iii) series compensation; (iv) shunt reactive power compensation; (v) harmonic compensation; (vi) load leveling; (vii) voltage stability improvement; and (viii) back-up supply. These UPFCs can provide improved power system operation and control, added system security and reduced power system losses.Power system stability improvement using energy storage with fuzzy logic controller
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000415
A fuzzy logic controller (FLC) is designed for a battery energy storage system (BESS) to improve the stability of an interconnected multi-machine power system. The studied system consists of two generating areas interconnected by a long transmission line. A detailed model of BESS is developed for accurate dynamic assessment. The model takes into account the switching actions of the converter as well as the battery characteristics. This paper also describes the use of hysteresis technique to control directly the BESS output current. This reduces the complexity of the control system while at the same time provides a tight control of the BESS output. Test results under a variety of disturbances show the proposed BESS is effective in damping out power system oscillations.Multifunctional digitally-controlled bidirectional three-phase soft-switching PWM converter
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000225
In this paper, a prototype of a multifunctional controlled three-phase voltage-source bidirectional zero voltage soft-switching PWM converter with three auxiliary active resonant commutated snubber link (ARCSL) is presented for battery and/or electric double layer capacitor energy storage system (BESS) and active power filter system (APFS). The operating principle of this active resonant snubber-assisted soft-switching converter circuit and multi-functional digital control-based converter system including active rectifier and inverter operation modes are described. The effectiveness of a soft-switching bidirectional converter system is proved on the basis of simulation analysis.ANN controlled battery energy storage system for enhancing power system stability
http://dl-live.theiet.org/content/conferences/10.1049/cp_20000416
This paper describes an application of an adaptive artificial neural network (ANN) controller to continuously control the charging and discharging of a battery energy storage system (BESS) to improve the stability of an electric power system. The simulation studies have included a detailed model of the generator including its excitation controller and governor, as well as a comprehensive BESS model, including the DC battery model and the switch operation associated with the power converter. An online training artificial neural network controller is continuously trained to directly control the BESS operation to damp power system oscillations in various power system operating conditions. Simulation results show that this ANN-controller can adaptively learn and update its control strategy to improve the system stability under different system operating conditions.Independent generator perspective: wind turbines as embedded generators
http://dl-live.theiet.org/content/conferences/10.1049/ic_19980394
Wind turbines are becoming a recognised part of the landscape, particularly in mainland Europe. The growth of wind generated electricity has been slower in the UK, although a few Public Electricity Suppliers (PESs) now have a significant number of wind farms connected to the distribution network. Wind energy currently provides around 2.5% of the total demand in Wales and nearly 40% of the electricity demand in Powys. This paper describes the implications for the electrical system with an increasing penetration of wind generation, drawing from experience of wind farm developments in the UK and other European countries. (4 pages)Evaluation of a new type of protection relay for wind farms
http://dl-live.theiet.org/content/conferences/10.1049/ic_19980398
A new type of relay suitable for the protection of wind farms has been described. The relay, installed at the utility end of a power collection circuit, is designed to protect the collection circuit and the LV and MV windings of each wind turbine generator transformer. The relay has been tested on-site at the Cemmaes wind farm and in a laboratory using the EMTDC simulator and an OMICRON relay test set. Numerous tests have shown that the relay remains stable during out-of-zone faults or nonfault disturbances and is sufficiently sensitive to operate on all realistic in-zone faults. (6 pages)A matrix converter excited doubly-fed induction machine as a wind power generator
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980583
A grid-connected wind power generation scheme using a doubly-fed induction generator (DFIG) in conjunction with a direct AC-AC matrix power converter is proposed. The analysis employs a stator flux vector control algorithm and a space vector modulated matrix converter to control the generator rotor current. The system enables optimal speed tracking for maximum energy capture from the wind and high performance active and reactive power regulation. The paper discusses the operating principles of this power generation scheme. The matrix converter-based rotor current control method is described. Simulation studies of the proposed power generation system were carried out. Results obtained are presented illustrating the good control performance of the system.Bi-directional power control for flywheel energy storage system with vector-controlled induction machine drive
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980573
Short-term energy storage devices with excellent cycling capabilities are highly desirable for use in conjunction with renewable energy resources such as wind and wave power systems. The paper presents a flywheel energy storage system based on a vector-controlled induction machine drive with bidirectional power control. A description of the power electronic drive and of the development aspects for adding fast-response active and reactive power controllers are given. Integration of the flywheel drive into the power system at the Rutherford Appleton Laboratory (RAL) Wind Test Site (WTS), is also described with the dynamic/supervisory controller explained. Practical results obtained via the dynamic controller and the instrumentation facilities at the WTS, demonstrating the time and frequency responses of the flywheel drive and those obtained from implementing the system with wind power smoothing configuration, are presented and discussed.Wind turbine power converters: a comparative study
http://dl-live.theiet.org/content/conferences/10.1049/cp_19980572
Two of the most promising types of power converter applicable to the task of interfacing variable-voltage DC energy sources to the grid are compared. The converters studied are first a DC/DC power converter with a current-controlled voltage source inverter and, secondly, the line-commutated SCR with an active compensator for reduction of harmonic current and reactive power demand. The comparison is drawn with particular reference to use with variable-speed permanent-magnet wind turbine generators. The optimal power transfer, reactive power/voltage regulation and harmonic minimisation are addressed. Experimental results from laboratory models are presented alongside simulation results, which are in good agreement, to demonstrate the power control and harmonic performance of these systems. Power losses and semiconductor costs are also discussed.Power conversion system for a modular, direct-drive, permanent-magnet wind turbine generator
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970915
Voltage regulation can restrict the useful capacity of permanent-magnet generators. For example, a single-phase permanent-magnet AC generator may be represented by an EMF source proportional to speed and hence frequency, with series reactance also proportional to frequency. The maximum power which can be delivered to a resistive load is proportional to speed and may be much less than the thermal rating. This problem became serious during the development of a power conversion system for a variable speed, permanent-magnet, wind turbine generator. The power available from the wind is proportional to the cube of speed but the generator capacity increases only as speed. The machine concerned is modular and intended for use as a direct-coupled, low-speed generator. The stator consists of modules each of which has an E core with a single coil producing a single phase AC output. The outputs are rectified separately and combined at a common DC link. The power limit imposed by the series reactance leads to poor utilisation and leaves little torque margin to cope with transient torque due to wind gusts. Consequently, some form of compensation is needed, particularly at high speed. The approach adopted was to employ a capacitor connected across the generator AC terminals. The capacitor may be considered to be part of a tuned circuit, cancelling some of the series inductance or alternatively it may be thought of as providing additional excitation due to the capacitive current flowing in the stator coils. (5 pages)Wind farm earthing
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971016
This paper examines the use of computer modelling to assess the suitability of windfarm grounding systems for protection against power system faults and lightning strikes. The transient behaviour of practical earthing system designs are presented using the general purpose EMTP program and the specialist CDEGS grounding analysis software. (3 pages)Large modular PM generators
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970521
Wind-turbine installations are increasing in size as economic and other factors stimulate their proliferation. To use a generator of conventional shape and parameters requires a gearbox of increasing size and ratio. The advantages of any arrangement which eliminates the gearbox are mostly obvious-the main disadvantage is an increase in the size of any electrical generator which is directly coupled to the turbine. In spite of this, the design of generator described in this paper is proving to be a viable proposition. A significant factor in cost and weight is the diameter at the air gap-the larger this is, the better utilised will be the active materials of the machine. A relatively small pole-pitch permits generation at near normal frequency, and the use of permanent-magnet excitation allows a small pole-pitch to be used without the usual penalties associated with poor coupling such as poor power factor. Both of these features have been adopted, together with a modular form of construction, in the machine described. The major aspects of the construction are: magnets in a 'buried' configuration with flux concentrators attached to magnet blocks to form a rotor module; stator magnetic material in the form of 'E'-cores with open slots, and in each of which is contained a single coil; and each 'E'-core attached to a support beam to form an isolated stator module. The main advantages of the construction are listed and discussed. (6 pages)Simulation of FACTS for wind farm applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970921
The simulation of FACTS (flexible AC transmission systems) is essential in order to provide insight on the interaction of FACTS, wind farm(s) and the grid prior to any application of such systems. A typical wind farm-FACTS arrangement is considered. Two FACTS-devices are utilised. Firstly a dump load sheds the extra power produced, or is activated during a wind farm cut out to prevent the isolated wind farm voltage to shoot up. A unified power flow controller (UPFC) is also considered which combines reactive power compensation (instead of an SVC) and voltage control (instead of a TCSC). The wind farm considered is comprised of 5 horizontal axis turbines, each having a capacity of 300 kW. The 3 blade hub is coupled to a step up gear and through a coupling mechanism (usually fluid), to an induction generator. Wind farm temporal and spatial dynamics as well as tower structural dynamics have also been considered. It is shown how SABER, a special simulation package built around MAST, was used to simulate a system containing a resistive brake and a UPFC. Finally SABER simulation results were used to indicate that the resistive brake can be used as a dump load for isolated wind farms and that the UPFC can provide both voltage control and the reactive power of a grid connected wind farm. (5 pages)Impact of embedded generation on distribution system voltage stability
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970570
Embedded generation is being connected increasingly to distribution networks. For many new renewable energy schemes, this will involve the connection of induction generators to weak rural networks. It has been shown by studies, and subsequent operating experience, that relatively high ratios of wind farm capacity to network short circuit level can be accommodated successfully if conditions are favourable. However, voltage stability of the power system is likely to be an important limiting factor to the continued increase of the ratio of generation capacity to network short circuit level. (4 pages)The effects of lightning on structures and establishing the level of risk
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971013
The high levels of energy, current, charge and rate of current rise associated with a lightning strike can result in a structure being severely damaged if struck. A key stage in determining the type of lightning protection system (LPS) required by a structure is the estimation of the lightning strike frequency. For each strike, the probability of the energy/current/charge/rate of current rise exceeding a specific value can also be found mathematically. The IEC standard detailing lightning protection of structures, IEC 1024-1: 1990, provides a method of calculating the lightning strike frequency to an object of no more than 60 m height. Considering modern wind turbines may have a hub height greater than 60 m, this standard is inapplicable to such machines. Of particular importance in tall structures is the possibility of upward propagating lightning strikes. The assessment of the total lightning strike frequency, both upward and downward propagating, can be assessed using two independent models. (3 pages)Power electronic converters for variable speed wind turbines
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970914
The incorporation of a variable speed function into a wind turbine has a variety of benefits, including: improved power yield during low wind speed conditions, reduced mechanical loading on drive train components, reduced audible noise, reduction in tower passing effects. The pulse width modulated (PWM) inverter has now developed to the point where it can economically and technically manage the power levels associated with commercial wind turbines using variable speed drives. The four quadrant transistor based PWM inverter using insulated gate bipolar transistor (IGBTs) is now available at power ratings up to 2 MW and has superseded the line commutated inverters previously employed for developmental variable speed wind turbines. The four quadrant-inverter system discussed in this paper is in effect two voltage source inverters in cascade. Also discussed are doubly fed induction generators and direct drive configurations. (8 pages)Fuzzy logic control of a unified power flow controller for wind farm applications
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970922
Due to the stochastic nature of the wind, the power fed into the grid from a wind farm is variable. This leads to a highly nonlinear variation in the terminal voltage. This variation depends largely upon the energy penetration of the wind farm, the load density at the wind farm node as well as the transmission line characteristics. A unified power flow controller (UPFC) is considered as a means of providing wind farm reactive power and maintaining the voltage of the local grid. To simplify the discussion only the control of the series branch of the UPFC is discussed in some detail. A classical control approach might be to use simple P+I controllers for both the series and shunt branches of the UPFC. However, the linearisation of power electronic devices plus the characterisation and the nonlinear nature of a wind farm makes it difficult to model accurately. Fuzzy logic provides an attractive alternative. It has a fairly straightforward theory and implementation. It does not necessarily require mathematical modelling of the system under control, but, the system dynamics need to be appreciated before the controller is designed. In the study the series branch of the UPFC is under fuzzy control whilst the shunt branch remains under P+I control. This paper is provided as a tutorial for fuzzy control as much more sophisticated forms of fuzzy (e.g. adaptive) and classical control (robust, optimal) methods are available. (6 pages)A practical example of the use of distribution static compensator (D-STATCOM) to reduce voltage fluctuations
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970920
Voltage fluctuations at the point of common coupling of the generator to the electricity supply network are an inevitable consequent of the variable nature of some renewable energy sources such as photovoltaics and wind power. These can be mitigated by a number of equipments but the fast response of the distribution static compensator (D-STATCOM) makes it the ideal solution. The author discusses active and reactive power flows, and reactive power compensation, and then describes the D-STATCOM and an application. (5 pages)Protection of wind turbines control systems from the induced effects of lightning
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971015
The control equipment installed in a wind turbine can be susceptible to induced voltage transients arising from a lightning strike. Transient levels are very dependent on small details of installation such as wire routing, and in this paper suggestions are made to minimise these lightning effects by simple installation procedures. (3 pages)The application of advanced static VAr compensators to wind farms
http://dl-live.theiet.org/content/conferences/10.1049/ic_19970919
Modern fixed speed wind turbines use induction generators which require a source of reactive power. Part of this requirement is usually supplied by local power factor correction capacitors (PFC) connected at the terminals of each turbine. The rest is supplied from the network, which can lead to low voltages and increased losses. Moreover, wind turbines are often installed at high wind speed sites which are remote, and have only weak electrical networks. In these cases, the effects of real and reactive power flows on the voltage quality are increased. Due to developments in power semiconductor devices and control techniques, the power ratings of convertor type VAr compensators have increased. Also, switching device costs are decreasing to a level where this type of equipment may provide a cost-effective method of improving the power quality of wind farms. In this paper some preliminary simulations of an advanced static VAr compensator (ASVC) to be commissioned on a wind farm are described. (5 pages)Overview of component damage by lightning and protection
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971014
This paper summarises the laboratory testing and field data obtained on wind turbine blades and bearings to date in the JOULE research programme. The conclusions presented are interim because work is still in progress. Blades are the second most likely item to be damaged in a lightning strike (after the electronics system) but the damage results in a much greater loss in output. Bearings, in contrast to blades, are often protected against lightning because they are on the path to ground and not too expensive to protect, rather than being seriously affected to any obvious extent. (4 pages)Lightning: safety and protection
http://dl-live.theiet.org/content/conferences/10.1049/ic_19971017
Lightning to tall structures, such as wind turbine towers, power poles, etc., results in relatively high transient voltages. These lightning generated voltages can cause insulation failures and generate safety problems for humans and animals in the vicinity of the strike. This paper addresses the issues relative to these phenomena and describes a model for predicting lightning effects on a wind turbine/generator tower. (7 pages)Structural design of medium-voltage networks considering dispersed generation
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970617
Dispersed generation in the distribution network, especially wind energy converters and unit-type district heating power stations have been growing in importance in Germany for some years. Since the owners of the networks and the companies managing the power stations in Germany are not usually one and the same, the degrees of freedom regarding the connection of the supply to the power stations often lead to differences of opinion. Existing guidelines on the connection of the supply to the power stations used by the energy supply companies are more often than not called into question by power station managers. This report shows, with the help of case studies, how the basic technical conditions can be investigated effectively and how the discussion can be objectified to the advantage of both sides. (5 pages)Power quality measurement and diagnosis using multifunctional equipment
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970503
The power quality of electrical energy has become a subject of great importance. Nevertheless, there are different approaches to the problems related to power quality, each of which involves the use of a different measurement system: the voltage characteristics must be evaluated using statistical methods, for which long duration measurement is needed; and the study of equipment and problem diagnosis require fast measurement which is very accurate. Waveform analysis is frequently necessary. For all these reasons, statistical treatment is not possible. Moreover, simultaneous measurement of several parameters is needed, as they are interrelated with each other. Consequently, large volumes of information are obtained, which are difficult to deal with and, on occasions, incompatible with each other. The need for two totally different measurement philosophies has led to the development of measuring equipment capable of combining the two systems mentioned. This article describes the application of multifunctional measuring in three real cases: an AC arc furnace, a DC arc furnace, and a wind farm. (5 pages)Real experience in the connection of wind power production in distribution network
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970607
For the implantation of the wind farm at the El Perdon site, numerous measurements were made of wind direction and speed. These measurements made it possible to predict a high number of hours of operation annually and an important energy production. Moreover, it was necessary to determine the ideal connection point to the network that would guarantee the removal (evacuation) of the energy produced and to study the impact of the wind farm in order to preserve the supply quality parameters already set by IBERDROLA. Finally, the results of real operation and the measurements carried out are shown, to prove that the voltage and frequency quality are as forecast. (5 pages)Distribution power quality improvements using dc links with battery storage in existing networks
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970482
The use of DC links with battery storage in LV distribution networks provides several advantages for both the final user and the electric utility. In particular, with the use of DC links between the LV windings of the distribution transformers and the load, the following advantages can be obtained: improvement of the power quality of the energy supplied to the user, in particular because the DC link with battery storage can eliminate short voltage interruptions and dips of up to a few minutes; and possibility of using a higher voltage level for the DC line than those presently used for AC lines, thus increasing the link power carrying capability. These features are very important in urban areas, where the installation of new power cables is costly (and sometimes very difficult to realise) and the request for power quality is ever increasing due to the growth in the number of electronic appliances. In this paper, several possible alternatives for realising such a DC link are presented and their feasibility is shown, both in terms of normal and faulty operation and of reliability. Some economic considerations are also dealt with, with particular attention given to a case study. (5 pages)Combination of renewable sources of energy and energy storage units for providing a reliable power supply for remote and isolated areas
http://dl-live.theiet.org/content/conferences/10.1049/cp_19971896
Renewable sources of energy such as solar and wind which are of intermittent nature are usually combined with one type of energy storage device. Combination of photovoltaic energy or wind energy with an energy storage device offers a more reliable electricity supply system which is needed for remote areas. The objective of this paper is to present a system model of a hybrid power system in which photovoltaic energy is used as an electricity generating unit and battery storage as backing up device.Economic impact on a conventional utility of non-utility generation producing energy from a non-conventional source
http://dl-live.theiet.org/content/conferences/10.1049/cp_19971840
When a utility buys electric energy from a nonutility generator (NUG) at short notice, such as a few hours, one of the difficult issues encountered by the utility is the evaluation of the rate (buyback rate) it should pay the NUG such that the utility maximizes its economic benefit. This problem is magnified when NUG produces energy from nonconventional source, wind. Short term buyback rates should be based on the operating cost that a utility avoids by utilizing energy from a NUG. This cost is termed as the avoided operating cost (AOC) in this paper. A comprehensive technique for a thermal power utility is developed to assess the short term AOC. The IEEE-RTS is considered to be a thermal utility in this paper, which is utilized to demonstrate the technique. Some sensitivity studies have been performed and selected results are discussed in the paper.Power quality and grid connection of wind turbines
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970476
This paper describes the effect of grid-connected wind turbines on the power quality in a distribution network. Special attention is given to stationary voltage conditions, flicker and harmonics. A probabilistic method has been developed for the analysis of stationary voltage conditions with the grid-connection of wind turbines. A method of calculating the flicker contribution of a given wind turbine to a given network is also described. The flicker contribution has been measured and analysed. Harmonics from pulse width modulation (PMW) frequency converter-connected wind turbines with variable rotational speed are evaluated. (6 pages)Design and evaluation of a new type of protection for wind farms
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970038
EMTDC is a nonreal time transient simulator designed by the Manitoba HVDC Research Centre. It incorporates a user-friendly, CAD style interface called PSCAD that allows the user to model a network by interconnecting pre-defined graphical icons that represent the components of the power network. This approach ensures that it is unnecessary to write any direct code, provided the existing models within the EMTDC libraries are acceptable. However, this does not preclude the user from defining their own custom models as graphical icons in an EMTDC component library. This paper indicates how the relative flexibility and userfriendliness of EMTDC, has allowed a new protection for wind farms to be modelled and tested within a simulator.Source based protection of wind farms using a multi-function protection relay - its design and site trial experience
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970572
Laboratory simulation, relay testing and a site trial have been used to both validate and develop a new type of protection for small to medium sized wind farms (0-20 MW). The protection, implemented within a multifunction relay, is sufficiently sensitive to detect all realistic in-zone faults and correctly discriminates with the LV fuses that detect LV cable faults. Similarly, the site trial has confirmed that the source based protection is stable during out-of-zone faults and other types of network disturbances. (5 pages)Damping inter-area oscillation using a battery energy storage system
http://dl-live.theiet.org/content/conferences/10.1049/cp_19971869
The paper describes some control strategies developed for battery energy storage systems (BESS) to damp inter-area oscillation, a growing problem to many utilities in the world, as more and more are dependent on interconnections. This paper describes the use of several control strategies of using different damping signals and controllers such as PI controllers and novel artificial intelligence control techniques such as fuzzy logic control to modulate the active and reactive power outputs of the BESS. Preliminary studies show that both types of controllers can provide significant damping. This paper also discusses how to determine the best location for placing BESS to damp inter-area oscillation, particularly when different control strategies are used.Contribution to the determination of the basic load proportion of non-centralised, regenerative power generation plants in the supply area of a regional power supplier
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970609
Under the German law on energy supply, the Energieversorgung Suedsachsen AG (EVS AG) as a regional supplier with more than half a million customers for both tariff and special contractual conditions, and presupplier to 12 urban plants with a maximum mains supply of more than 920 MW has the obligation to collect and enrich energy which was generated by noncentralised, regenerative power sources. Within the framework of wind measurement programmes, a possible extension of about 360 MW was determined for the supply area of the EVS AG. Based on new developments on the wind power plant market with the clear trend to the erection of wind power plants in the country, this value seems to be feasible in the future. For water power stations, a possible, installed, total capacity of about 40 MW with an increase to come mainly from the extension of formerly shut-down plants is assumed for the future. Feeding by photovoltaic plants is not a relevant scale. In October 1996, the installed capacity of wind power plants amounted to about 34 MW, and of water power plants, to 35 MW. Since the EVS AG does not have independent generating plants, and receives the entire capacity from presuppliers, it is becoming necessary to assess the capacity potentials of noncentralised, regenerative power sources in order to obtain an information on the sum of the monthly guaranteed proportions. The quantity of the energy which is made available by regenerative energy sources at a certain time cannot be ascertained in a deterministic way. The problems arising from an offer-dependent supply can only be dealt with by methods of probability calculus. (5 pages)Improving power system operations and control utilizing energy storage
http://dl-live.theiet.org/content/conferences/10.1049/cp_19971907
This paper describes several control strategies to utilise a modern battery energy storage system (BESS) to provide simultaneous control of both its MW and MVAr outputs to improve power system operation and control with the following objective in mind: ability to absorb harmonics, provide load leveling, provide damping of inter-area oscillations, help in damping transient stability, provide effective and fast control power flow along a transmission line corridor, in many ways acting like flexible AC transmission system (FACTS) devices, provide back-up electricity supply on loss of AC supply very similar to UPS applications and provide active power filtering to meet power quality standards. This work shows that BESS offers an important resource for improving power system control.Design and commissioning of a 2.5 MWh battery energy storage system
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970479
Momentary and sustained power interruptions are one of the most difficult and important power quality problems facing many industrial and commercial users. A particularly challenging problem is the need to supply an economical, dependable, efficient and controllable source of real and reactive power, which is available instantly to support a large (>1.0 MW) load, if the electric utility connection is lost. Battery energy storage systems (BESS) have the potential to provide versatile solutions to this problem for utility, industrial and commercial applications. This paper describes the design and installation a 5 MW peak, 2.5 MWh BESS which is now in commercial operation at the BNG Battery Recycling Facility in Vernon, California, USA. Results of commissioning tests are discussed. The BESS at Vernon provides the required power combined with both voltage and frequency control necessary to allow the Vernon facility to tolerate disconnection from the electric utility grid without suffering unacceptable impacts on critical loads. (5 pages)The effect of wind parks on the operation of voltage control devices
http://dl-live.theiet.org/content/conferences/10.1049/cp_19970608
The penetration of wind generation in distribution networks is increasing and is expected to increase further in the near future. In the case of weak networks, serious concerns are expressed regarding the degradation of quality and the increasing needs for compensation and more efficient control strategies. This paper presents the effects of wind turbine operation on the distribution network operation expressed as probability density functions of voltages along the feeder and it proposes a method for the adjustment of voltage control devices based on probabilistic constrained load flow. It is shown that the method leads to operation of distribution networks with increased wind power without voltage limit violations and fewer adjustments in the control setpoints. (5 pages)