c6 101 distributed generation business modelling. busmod ... · distributed generation business...
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DISTRIBUTED GENERATION BUSINESS MODELLING. BUSMOD PROJECT
I. GARCÍA BOSCH* – IBERDROLA (Spain)
I. LARESGOITI, C. MADINA – LABEIN (Spain)
A.Z. MORCH – SINTEF Energy Research (Norway)
J. GORDIJN, V. KARTSEVA – VUA (The Netherlands)
In the last few years, many countries have been deregulating their electric systems. This processopened up market opportunities for Distributed Generation (DG), but it also increased the amount ofparticipants and the complexity of the market interaction and network management. Taking this newenvironment into account, seven partners from five different European countries started working in theBUSMOD project.
The main result of this project has been a DG business modelling methodology, which will allow DGbusiness developers to make easier feasibility studies for new DG businesses. The methodology hasbeen tested using several business scenarios, which are the other project goals.
The BUSMOD methodology is based in the e3-value methodology, a methodology used in innovativee-commerce businesses. The e3-value methodology has been adapted to the special characteristics ofDistributed Generation. To that end, the SWOT analysis (Strengths, Weaknesses, Opportunities,Threats) analysis was carried out to determine which DG characteristics could impact the feasibility ofnew businesses.
One of the main conclusions of the SWOT analysis was that the regulatory environment influences toa big extent the feasibility of a DG business. As a result, one business idea may be feasible under aregulatory environment, but lead to bankruptcy under another legislation.
The BUSMOD methodology guides the user in the development of a business idea through a set ofsequential steps. The first step consists in describing the business idea. Afterwards, some steps, suchas the identification of the actors involved in the business or the value objects exchanged betweenthem, lead to a final value model, which gives a graphical representation of the business. Then, thefinancial analysis is performed to determine the profitability for every stakeholder involved in thebusiness, the Net Present Value (NPV) is used for these purposes. Finally, the sensitivity analysis hasto be performed, so that the influence that different characteristics have in the profitability of everyactor involved can be observed.
The BUSMOD methodology shows the feasibility for all actors involved in the business. For a DGbusiness to be feasible, the profitability of every actor must be positive, since an actor with a negativeprofitability will not enter the business, which might lead to the failure of the complete business.
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As an example of the methodology application, this paper presents the results obtained when theBUSMOD methodology was used to analyse the feasibility of a Local Producer scenario in Norway.In this scenario, a Local Producer owns generating facilities and produces electricity, and sells it to anElectricity Supplier, who sells that electricity to Final Customers. The DSO provides grid connectionto both Final Customers and the Local Producer, and demands a grid connection tariff.
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INTEGRATION OF OFFSHORE WIND FARM IN THE POWER SYSTEM
Jacques Courault Guillaume de Préville
AREVA T&D
Transmission Projects Business Power Electronics Activities
9 rue Ampère 91345 MASSY FRANCE
Abstract – It is quite difficult to discuss the possible solutions for the connection of windmills within a high-power farm and the distribution of energy to users networks, without addressing the global problem of electricity production from an random wind source.
This article, which refers to other specialized publications, considers the global problem of the integration of a wind mill in a power system. Small scale integration and large scale integration have to be differentiated as power quality problems will differ
Most of today’s wind mill installed worldwide is equipped with fixed speed asynchronous generators, directly coupled to the network. With the progress in power electronics and inverter technology, the indirect grid coupling with variable speed operation associated to active blade angle control become very attractive, as it improves the power quality and facilitates large scale integration.
After recalling a number of data and basic indirect conversion structures, the paper comes to an open comparison between both possible solutions of distribution, AC or DC. Key words – Windmills, wind farms, active power control, reactive power control, synchronous and asynchronous machines, filters, SVC, HVDC.
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DECISION – SUPPORT INFORMATION SYSTEM FOR EVALUATING THE PENETRATION OF DISPERSED RENEWABLE ENERGY SOURCES GENERATION IN TRANSMISSION AND
DISTRIBUTION NETWORKS
D. AGORIS* (1), K. TIGAS(2), V. KILIAS(2), J. KABOURIS(3), T. KORONIDES(3) J. VLACHOS(2), M. PSALIDAS(1), E. PYRGIOTI(1)
(1) High Voltage Laboratory, University of Patras (2) Centre for Renewable Energy Sources
(3) Hellenic Transmission System Operator
Greece SUMMARY
The development of Renewable Energy Sources in Greece has been among the major energy policy lines for the last 10 years. Under these developments, all the parameters concerning the implementation of wind energy and small hydro investments should be evaluated, in order to access the “technically and economically exploitable wind and small hydro energy potential” in wide geographic areas. A decision-support software tool based on a Geographical Information System (GIS) has been developed, to produce penetration plans of dispersed renewable energy sources (RES) generation in transmission and distribution networks. The tool is taking as input the physical potential of wind energy and small hydro and other various parameters related to existing infrastructures, land use and availability, high voltage network, energy technologies characteristics as well as costs and schemes for financial support. The output of the system includes calculations of the available potential of RES, expected energy production by each candidate RES project and the implications of RES penetration on transmission and distribution networks, under different RES penetration scenarios. Finally, the tool calculates economic indicators for the evaluation of the economic potential of RES in given geographical areas. To correlate the potential information, having a strong geographical character, with the electrical network, in order to study penetration problems, a module of the system has been developed, for digitizing under a GIS platform the electrical network, named e-Zeus. The electrical network management module digitizes the electrical network combining electrical topology information, geo-information for the distribution of the electrical network and other geographical information of the area of interest. These data are stored in a geo-database and constitute the basic input for the two major applications of the module, the technical and economical study for the connection to the grid of RES projects. The user can apply different scenarios with various connection schemes and verifies the smooth system operation under different conditions. Steady state network analysis is performed for each scenario in order to examine the system’s transfer capability by detecting any over-loadings of transmission lines, to verify voltage profiles at substations and to determine any required network reinforcement needed. Transient analysis can be also performed via interface with the EMTP-ATP. The decision support system has been applied to evaluate the technical and economical available potential for RES installations in Greece. Some indicative results for the windiest area of Southern Evia are presented. Also a detailed application for the electrical network management module in Lakonia is presented in the paper.
KEYWORDS
Renewable energy, wind energy, small hydro, decision support software, geographical information system, distributed generation, high voltage network.
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DISTRIBUTED GENERATION IMPACT ON OHMIC LOSSES AND INVESTMENT DEFERRAL IN DISTRIBUTION NETWORKS
Juan Rivier*, Tomás Gómez, Víctor Méndez Jose Arceluz, Javier Marín Instituto de Investigación Tecnológica IBERDROLA Universidad Pontificia Comillas (SPAIN) (SPAIN) A new paradigm for electricity networks is getting stronger in the last years. Electrical power systems are evolving from the nowadays centralized bulk system with generation plants connected to the transmission network to a future decentralized system with smaller generating units connected directly to distribution networks, near demand consumption. Various reasons are at the core of these changes. Environmental consciousness and sustainable development based on long term diversification of energy sources are key aspects on the agenda of energy policy-makers. Renewable energy sources tend to be small and dispersed. Competition in wholesale electricity markets can be increased as a consequence of numerous and small new entrants. Finally, potential distribution network cost reductions can be achieved because distributed generation (DG) connected near demands will decrease the need for transmission and distribution network reinforcements and investments. This paper analyses precisely DG connection impacts on distribution networks. A methodology has been developed to assess such impacts on distribution feeder ohmic losses and network reinforcement deferrals as demand increases. The results show that losses variation on distribution networks due to DG have a sort of “bathtub curve” behaviour. In general, for low DG penetration levels, losses decrease, but for higher penetration level losses marginally increase and even can be higher than losses in the base case. A higher penetration level of DG can be positive in terms of loss reduction if DG is highly dispersed in the feeder. An the voltage control at load points where DG is connected have great influence on losses level. The results show too that, once initial reinforcements to accommodate DG connection have been implemented, DG can defer network investments in the face of expected natural load growths. This impact on investments deferral depends on DG technology. CHP plants have a more positive impact than wind turbines, due mainly to a highest randomness of wind energy production. Photovoltaic may have a high positive impact depending on the load profile. Finally, DG concentration along the feeder has also an important effect on investment deferrals. The more dispersed DG units are located along the network the better is their impact. This effect is explained because of the improvement of DG total availability and because of the complementarities among energy production patterns from each DG unit.
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Summary During recent years, a substantial scaling up has taken place in the wind power area. This applies both to the size of the individual turbine and to the scale of the typical project. For modern wind turbines of the multi-MW class, both the nacelle height and the rotor diameter are in the order of 100 m. Thus, at the vertical position, the blade tip can reach up to heights of 150 m. Further, in order to use good wind locations effectively and to geographically concentrate the visual impact of wind turbines at certain locations, a tendency to group wind turbines in wind parks, or wind farms, can be observed. In densely populated countries adjacent to shallow waters, such as many countries in Northwest Europe, construction of offshore wind farms is considered a promising option. Advantages of offshore wind power are reduced visibility and noise problems and steadier winds with higher average speeds, resulting in a higher energy yield. Disadvantage is the cost increase when compared to onshore turbines, caused by the additional cost of constructing offshore and the longer distance that must be covered for connecting wind turbines to the grid. In the paper, various aspects of the impact of wind power on power systems in general and on the Dutch power system in particular are discussed. First, an overview of the development of wind power in The Netherlands is given. It is concluded that during the last years, the installation rate increased and that ambitious plans exist for the future. Then, the local and system-wide impacts of wind power are discussed. It is concluded that wind power has both local and system-wide impacts, due to the fundamental differences between wind turbines and conventional generation technologies: wind turbines use an uncontrollable prime mover, the wind, and generator types different from the synchronous generator normally used in conventional power plants are applied. Wind power locally has an impact on the following aspects of a power system: branch flows and node voltages, protection schemes, fault currents, and switchgear ratings, harmonic distortion and flicker. System-wide it affects power system dynamics and stability, reactive power and voltage control, frequency control and load following/dispatch of conventional units. The origin of these impacts, as well as mitigation measures, are discussed in the paper. Further, electricity storage is treated. It is concluded that electricity storage is an option for balancing the wind power output, but that it is in most cases still too expensive to be seriously considered. Finally, the grid connection of wind parks is investigated. This leads to the conclusion that conventional AC technology is still preferred for connecting wind parks to the onshore grid. Keywords Wind - Offshore - Storage
Considerations to the electrical network interaction of 6.000 MW offshore wind parks in the Netherlands in 2020
C.P.J. Jansen*, R.A.C.T. de Groot, KEMA T&D Consulting, Arnhem, the Netherlands.
J.G. Slootweg, Electrical Power Systems Laboratory, Delft University of Technology; Essent Netwerk Noord B.V., Zwolle, the Netherlands.
J.H.R. Enslin, KEMA Inc.- T&D Consulting, Raleigh, USA.
W.L. Kling, TenneT bv, Arnhem; Electrical Power Systems Laboratory, Delft University of Technology, the Netherlands.
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Summary Legislation passed in April 2000 and governing the infeed of regenerative energy compels network operators to link up to all the renewable generating sources and to purchase all the power generated for a specified infeed remuneration. Since this law came into force, in Germany there has been a notable increase in the proportion of power generated from renewable sources, particularly wind energy. Figures for late 2002 show a total installed wind power of about 12,000 MW, with a maximum load capacity in Germany of 80,000 MW. 50% of this installed wind power is placed in the Transmission System of E.ON Netz and 35% is placed in the Transmission System of Vattenfall Europe Transmission. Further expansion (especially in offshore regions) up to a figure of 25,000 MW by the year 2030 is planned. Nearly all these generating units provide their infeed in an unregulated manner, depending on available wind and regardless of network load. By its very nature, wind energy infeed is stochastic and difficult to foretell. Wind predictions are based on weather forecasts and depend therefore on the accuracy of the latter. This means that load forecasts are subject to uncertainty spans of up to 15% on average. Additional reserve capacity must therefore be provided. As a result of unbundling (specified in the EU Directive of 1996, which was fully implemented in Germany), transmission network operators no longer possess their own generating plants and have therefore to purchase their power on the market. The absolute priority attached to renewable energies is detrimental to generation from conventional power stations. Particularly in periods of low demand, in conjunction with strong wind, there is a lack of controlling power in the network, owing to the low proportion of conventional generation. This calls for controllability of power generation. It is important to arrive at an optimal balance, in both economic and technological terms, between controlled wind energy infeed and the supply provided by conventional power plants. It is mainly northern Germany where wind energy is making progress. This region has hitherto accounted for relatively low electricity demand, with the result that the transmission network is not as substantial as elsewhere. The planned construction of more offshore wind farms in the North and Baltic Seas will lead to increasingly frequent bottlenecks in the transmission network in a north-south direction. Intensified use of wind energy will therefore necessitate improvements to the transmission network. Extension of wind energy requires a corresponding extension of the grid. Network access regulations equivalent to those for conventional power stations have to be applied in future to wind farms with power infeed into the HV grid, too. This means for example that in the event of a short circuit near the point of common coupling a wind farm must, up to a fault duration of 150 ms, remain stable and connected to the network. Most of today’s wind generator types are not capable of this behaviour. Suitable models of wind generators must therefore be developed, allowing an examination of the dynamics of such units, and with the aid of which the requirements imposed on the network (especially the power electronics) can be derived. Linking up large offshore wind farms to public networks over long distances is a complex technological challenge. This paper presents suitable basic concepts in the form of AC or DC solutions; the technological and economic contextual conditions are discussed. The political activities concerning the promotion of wind energy must not overlook the fundamental technical problems; these can only be solved by the joint efforts of all concerned (e.g. wind generator manufacturers, wind farm operators, network operators and their associations).
Influence of Increased Wind Energy Infeed on the Transmission Network
Yvonne Sassnick, Matthias Luther, Ronald Voelzke* Vattenfall Europe Transmission GmbH, E.ON Netz GmbH, Siemens AG
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Development of Autonomous Demand Area Power System
S.UEMURA�, H.KOBAYASHI The Central Research Institute of Electric Power Industry
(Japan)
Centered in urban areas with high power demand densities, the introduction of distributed power
generations is expected. Under such circumstances where many distributed power generations are incorporated in the existing power system, power flow congestion and voltage fluctuation on distribution lines, caused by varied output of the distributed power sources, will occur. This will make the control of the entire power system operation complicated, and result in a failure to maintain power quality and supply reliability by conventional power system management.
As a strong countermeasure of the issues, we have proposed a unique, new power supply system (referred to as the 'Autonomous Demand Area Power System' [ADAPS]). The system makes full use of the characteristics of distributed power sources, which feature the effective use of electric power and thermal energy at the demand side, in addition to cost reductions on the power supply side. Thus, both customers and power providers benefit. To facilitate this proposed scheme, we will try to establish network technology and operation management technology of the ADAPS, and identify its effectiveness.
The facility formation of ADAPS is required to flexibly deal with power flow congestion due to the interconnection of multiple distributed power sources, and increased power demand in urban areas, without any complicated control techniques. In addition, to deal with the difficulty in obtaining land for new power plant construction, as well as prevent complicated power system configurations and cost increases, this proposed system must maintain a stable power supply reliability for a longer period, without frequent strengthening of related facilities even when distributed power sources and/or demand may increase.
The proposed system may be in the loop formation, in addition to the conventional tree branch form. Loop Controllers for controlling power flow and voltage between loops will be needed. At the supply side, the operation control system and multiple S&D interfaces per several customers will be installed for information exchange between supply and demand sides. The operation control system (central unit) aims for power flow control of whole of the ADAPS. At the time of a failure occurrence, the system (sub unit) detects the faulty section, and executes power interchange for sound sections and restoration by utilizing each S&D interface and Loop Controller.
Results of computer simulation using this system and operation technique confirmed that distribution system loss reduce to about 70%, availability factor become more equal to about 80% and voltage fluctuation reduce to about 60%. Moreover, results of computer simulation at fault confirm that faulty section of distribution line is detected using section switch with sensor.
We are also constructing a large-scale demonstration test facility called Hybrid-typed experimental facility of ADAPS. We set the prototype of components of ADAPS such as operation control system, S&D interface and Loop Controller. We set various distributed power generations. This capacity is about 50% of the feeder capacity in this facility. We made experiments about the voltage fluctuation and the voltage fluctuation reduced to 55% by controlling LPC. We are making experiments for operation control system by using whole ADAPS. Moreover, we are developing the techniques of controlling each component. We will confirm that ADAPS will be effective for the distribution power system introducing many distributed power generations. Keywords Distribution power system, Loop system, Protection system, Distributed power generation, Power electronics, Information and communication system
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To cope with restructuring an electricity market, connection of various kinds of dispersed generations to a power distribution system, which are spreading recently, will affect reliability and stability of power distribution system, though it is also expected to play an important role of operating system efficiently. Especially in terms of the power quality, while the conventional distribution system has been constructed as a branch which voltage level are getting down from the substation to the end, an increase of voltage due to a reversed power from dispersed generations is concerned. For resolving these problems, we have developed following systems. • An advanced central voltage control method that directly monitors current and voltage through the
sensors on distribution feeder. • A simulation system that enables calculation of power quality effect in advance, and supports
analyzing its improvement plans. Conventionally, voltage control has been conducted by local devices such as LRT (Load Ratio
Control Transformer) in substations and SVR (Step Voltage Regulator) on feeders. They independently estimates the voltage at target position (usually the center of spread load) from measured voltage and current values only at its installed position, and decides its proper tap position so that the target point voltage stays in its proper working range. However this approach has the problems that reverse current from dispersed generators and unequal load make the voltage profile on feeders complicated and increase voltage estimation error at target position. So we propose a central voltage control system shown in Fig.1 to resolve above problems, which composed two procedures; 1) estimating voltage and load profiles on the target feeders from current and voltage information measured by sensors, 2) settling the most suitable combination of LRT / SVR tap positions through discrete optimum power flow calculation. The discrete optimum power flow calculation scores to all possible combinations based on a valuation function, and select a combination to lead the most desirable voltage profile.
Secondary, various studies on the power quality of the distribution system such as voltage fluctuation, protection system coordination, protective relay setting calculation, instantaneous voltage drop, flicker phenomenon measurement and support function system have been conducted to reduce unbalanced voltage. However, it was difficult to develop a supporting system that covers all the questions and functions with a simple interface for system operators. Therefore, we have been developed a simulation system that includes various functions to support advance examination, such as to recognize the influence of voltage fluctuations or flicker caused by a change in the distributed resources or special loads, and to reduce the unbalanced voltage
Main functions of the system are the follows. (1) Power system information management (2) Calculation of voltage fluctuation (3) Protection system coordination for short-circuit contingency (4) Evaluation of instantaneous voltage drop and flicker (5) Support function to reduce unbalanced voltage (6) Influence of wind turbine connection
Development of Advanced Systems Corresponding to the Connection of Dispersed Generation to Distribution System in Tokyo Electric Power Company
J.Motohashi, K.Taguchi (Tokyo Electric Power Company) T.Takano� M.Watanabe (Mitubishi Electric Corp.)
M. Watanabe, K. Ogawa (Hitachi,Ltd.) (Japan)
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TransmissionNetwork
DispsersedGenerator
RS CS TR RDTD CDTALK / DATATALK
RS CS TR RDTD CDTALK / DATATALK
DistributionNetwork
Sensor
Tap Controls for�LRT ESVR
LRT
RS CS TR RD TD CDTALK / DATATALK
Switch
Measurement ofVoltage /Current
Voltage ControlSystem
1) Voltage Profile Estimation from Measured Voltage and Current2) Best Combination Settlement of LRT/ SVR tap positions through Optimal Power Flow Calculation
SVR
6.6‚‹V(Base)
VoltageUpper Limit
Lower Limit
Estimated Profile
Decides tap control combination so that thevoltage profile will go into regular range.
Distance
Fig. 1 Outline of Central Voltage Control System
Fig. 2 Example of a main window and dialogue boxes
SVR tap change
voltage profile load flow result
calculation setting dialogue
Fig. 3 Examples of the simulation setting and result dialogue windows
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ABSTRACT Studies of the wind energy for electric power generation in Mexico have had an important advance in recent years. Energy national organisms have had the common purpose of achieving the exploration and commercial exploitation of important renewable resource in our country. Currently the recognition of a program has not been achieved that contemplates the construction of wind plants. Works of exploitation, identification and assessment have continued in order to find feasible places for installation of wind plants and permits diversification of the national electric system including sources of clean energy. Programming Management of Electric Systems in coordination with the Management of Geothermal Projects carried out the technical-economic evaluation of the wind project La Venta II 50 MW using different planning models and also it is analyzed the environmental impact because of its inclusion in the national electric system. This technical and economic analysis will supplement the study of feasibility of the project that this carrying out the consultant company Global Energy Concepts under the patronage of the USAID (U.S. Agency for International Development). Different ways of representing the wind plants in the planning models MEXICO, WASP and VALORAGUA allow obtain technical-economic evaluations that sustain the viability of the project and this type of projects of renewable energy can incorporate in the national electric system. Additionally it is analyzed the environmental impact including the wind project in the system with DECADES model, calculating the reduction of CO2 emissions, when generation units operating with fossil fuel are replaced. Also are evaluated the additional benefits that represents the obtaining of the green funds.
TECHNICAL-ECONOMIC AND ENVIRONMENTAL STUDY OF THE WIND PROJECT LA VENTA II
Jorge FERNÁNDEZ ∗ Miguel Ángel ÁLVAREZ
Comisión Federal de Electricidad
(México, D.F.)
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C6-201
New solutions for power quality problems due to a large share of wind power generation
Achim SCHNEIDER*, Jürgen HOGRÄFER
SAG Energieversorgungslösungen GmbH, Germany
Volker PITZ, Michael SCHWAN FGH Forschungsgemeinschaft für Elektrische Anlagen und Stromwirtschaft e.V. , Germany
Holger LANGE Jürgen DECKERT Werner HERB RWE Net AG, Germany Thepault S.A, France Tessag Iberica SA (Foteha), Spain
(International) The appearance of wind power generation has changed dramatically during the last years. In the early years the generation of electrical energy using wind turbines was characterized by single units with limited power feeding into the distribution system, preferably in medium voltage level. Today’s technology is characterized by large wind parks consisting of units with a rated power of 1.5 MW or more connected to high-voltage distribution systems or even the transmission system. Effects of wind power generation on power quality have changed accordingly.
On the other hand, new problems arise or gain in significance with the growing density of wind farms. It is not only the variation of the power output but also the limited short-circuit power which might cause problems, when the portion of wind power fed into a system achieves remarkable levels. This leads to stricter rules for the connection of wind power plants to the grid as well as to new concepts for planning and operating the grids. This paper will illustrate the possible problems caused by high wind power generation and discuss the requirements to WECs consequently in detail.
Moreover a new approach to trim WECs to power plant properties is presented. The concept focuses on weak points of existing WECs: A new solution should provide a better short circuit behaviour, the ability of auto-reclosing and should be able to bear voltage drops or over-voltages as well as increases or decreases of the grid frequency. To supply the loads with the right power and to operate the grid at its best (overall) efficiency, reactive power has to be provided. Since these wind farms could be far away from the next grid connection point this ability could be used to compensate parts of the cable impedance of the connection as well.
Computer simulations show in principle the feasibility of the chosen approach. However, some of the restrictions cannot be avoided, i.e. the variation of power produced by the stochastic system "wind". The shown approach should therefore be seen as the fist step to reach the aim of a WEC with power plant properties.
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SUMMARY In the new environment of electricity market an increased interest has been focused on the development and use of alternative energy resources rather than tradition fossil fuel. Fuel oil uncertainties such as, scarcity, price escalation and public environment awareness brought a flurry to wind energy. This paper, proposes a technique to estimate the reduction in conventional electric capacity in presence of Wind Turbine Generators (WTGs) keeping the same overall reliability of the system. This reduction is called WTGs capacity credit. Furthermore, it presents a technique to examine the impact of integrating WTGs with the composite power system from a reliability point of view, taking into consideration the dynamic behavior of the system due to either a sudden loss of large generating units or loads. The proposed approach is a combination of the conventional deterministic approach and probabilistic method to calculate Loss of Load Expectation (LOLE), Expected Energy Not Served (EENS) and Demand Not Served (DNS) before and after integrating WTGs into the system. The proposed approach was applied to the Unified Egyptian Electricity System. The results presented prove that the WTGs can be considered not only as a fusel fuel saving units but also as a capacity credit, which affect the composite system reliability depending on the WTGs capacity, however the relation between WTGs installed capacity and its capacity credit is nonlinear. Thus, the financial competitiveness of WTGs in a deregulated market has to be further examined based on its capacity as will as reliability effects. WTGs integration with the conventional system needs different operation strategies in order to maintain the system overall reliability target level of operation during low reliability of other types of unconventional units (hydro) . Furthermore in case of big WTGs installed capacity, its energy may be discarded at one or more of the operating states to maintain system reliability within system characteristic limitations as well as maintain the economic operation of the system which is a decisive factor in a free deregulated electricity market.
WIND ENERGY IMPACT ON THE RELIABILITY OF COMPOSITE POWER
SYSTEM IN RESTRUCTURED ELECTRICITY MARKET
MOHAMED El-SAYED Electrical Engineering Dept., Cairo university
MOHAMED S. ElSOBKI (Jr.)1 Egyptian Electricity Regulatory Agency
EFFAT MOUSSA Egyptian ElectricityHolding Company
Egypt
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C6-203
Small, modular generation technologies interconnected to low-voltage (LV) distribution systems have the potential to form a new type of power system, the MicroGrid. These microgenerators are small units of less than 100 kWs, most of them with power electronic interface, using either Renewable Energy Sources or fossil fuel in high efficiency local co-generation mode. Both of these technologies are critical to reducing Europe’s GHG emissions and dependence on imported fossil fuel, where the MicroGrid concept will allow their most effective implementation.
MicroGrids may use single-phase circuits and be loaded with single-phase loads. These factors generate unbalanced conditions that can be accentuated with the interaction of dynamic loads such as induction motors. To model these effects, analysis tools must model the system with its three phases, the neutral conductors, the ground conductors and the connections to ground. The developed analytical tool should include steady state and dynamic models for the various forms of micro-sources and their interfaces. In the EU funded MICROGRIDS project (Contract ENK-CT-2002-00610) a simulation platform able to simulate the steady state and dynamic operation of LV three-phase networks that include micro generation sources is under development. This involves the development of adequate models in the time range of ms of the LV network, micro sources, machines (induction and synchronous machines) and inverters are developed. Normally these devices are directly coupled to the grid and thus have a direct impact on the grid voltage and frequency. Since the MicroGrid may use single-phase circuits and be loaded with single-phase loads, the simulation tool must model the system with its three phases, the neutral conductors, the ground conductors and the connections to ground to be able to deal with unbalance in the three phases. In this paper the following models are described: • Induction Generators • Wind Turbines • Photovoltaic Systems • Fuel Cells • Microturbines
Modelling of Micro-Sources for Security Studies N. HATZIARGYRIOU* G. KARINIOTAKIS N. JENKINS J. PEÇAS LOPES J. OYARZABAL F. KANELLOS X. LE PIVERT N. JAYAWARNA N. GIL, C. MOREIRA Z. LARRABE National Technical Ecole des Mines UMIST INESC Porto LABEIN University of Athens de Paris GREECE FRANCE UK PORTUGAL SPAIN
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Emphasis in given to the modelling of the power electronic interfaces and their control for both grid-side and machine-side. The integration of the above models in a steady state and dynamic simulation tool will provide a simulation test platform, which will be necessary to define and evaluate the developed control strategies. References Technical Brochure, CIGRE Task Force 38.01.10, “Modeling New Forms of Generation and Storage”, Nov. 2000. * Nikos Hatziargyriou, National Technical University of Athens, 9, Heroon Polytechniou, 157 73 Zografou, Athens, Greece, Tel. +3021-7723661, FAX: +3021-7723659, e-mail: [email protected] Study Committee C6 (Distribution Systems and Dispersed Generation), Preferential Subject PS2 (Role of dispersed generation in power system reliability, security and quality of power supply)
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C6-204
The paper provides results from the analysis of the economic and security impacts that Wind Power has on an autonomous power system. The largest autonomous power system in Greece,(471MW peak load during 2001), the Cretan Power system was studied using actual time-series of load and wind production. The Cretan power system operates with increased Wind power penetration (installed Wind Farms 67.35ΜW) occasionally reaching more than 30% in low load periods, whereas the wind penetration in annual energy is 10%.
Isolated networks with increased wind penetration, like the Cretan power system, face several Dynamic security problems. On-line Dynamic Security Assessment is therefore a key issue in operating the network in a secure way, detecting insecure dispatching configurations in preventive way and providing on-line monitoring of the system. Methods using Artificial Intelligence techniques, such as Artificial Neural Networks and Decision Trees have been developed within an advanced control software developed within the European Project “More Advanced Control Advice for secure operation of isolated power systems with increased Renewable Energy penetration and storage” (MORE CARE- Contract ERK-1999-00019). This software is installed in the EMS of Crete, to provide on-line assessment for major disturbances. On-line Dynamic Security Assessment functions are interfaced with Unit Commitment and Economic Dispatch so that the most economic and secure operating strategies are provided as figure 1 depicts. Results from the analysis of representative cases are included in the paper.
Off-line application of this software tool on past load and wind time-series allows evaluation of the dynamic security of the system, as it has operated on Crete and comparison with the assumed case with no Wind Farms operating. Results from this comparison are also included in the paper.
The financial contribution of Wind Power to reducing energy costs is studied next. This is evaluated by assuming that the Conventional Units would produce the energy the Wind Farms have produced in the period studied. It is supposed that the output of Wind Farms is zero every hour of a whole year and the already committed Conventional Units were dispatched optimally in order to meet the demand. The Sequential Quadratic Programming Method is used to optimise the non-linear objective function of fuel costs subject to technical constraints.Using the above algorithm for a whole year, the annual cost of producing energy for the Cretan System without the availability of wind power is calculated and the results are presented in the paper. It should be noted that the tariffs provided to Wind Power producers amount to 90% of the retail price. Nevertheless, a substantial reduction in the system operating cost is noted because of the fact that expensive fuel is replaced by Wind Power . The economic performance of the system using advanced control tools, like the ones developed within the MORE CARE EU project, is further examined. It is shown that optional operation of the system can reduce operating costs even further. General conclusions about the security and financial effects of large scale integration of wind power in island systems are finally drawn.
Security and Economic Impacts of High Wind Power Penetration in Island
Systems
N.HATZIARGYRIOU1*, A.TSIKALAKIS1,A.DIMEAS1 ,D.GEORGIADIS1,
J.STEFANAKIS2, A.GIGANTIDOU2, E.THALASSINAKIS2
1National Technical University of Athens, 2Public Power Corporation S.A.
(GREECE)
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Figure 1 Dynamic Security Assessment interfaced with Unit Commitment and Economic Dispatch
Schedules. Study Committee C6 (Distribution Systems and Dispersed Generation) Preferential Subject PS2 (Role of dispersed generation in power system reliability, security and quality of power supply).
IMPACT OF LARGE SCALE DISTRIBUTED AND UNPREDICTABLE GENERATION ON VOLTAGE AND ANGLE STABILITY OF TRANSMISSION
SYSTEM
Vu Van Thong* D.Van Dommelen Johan Driesen Ronnie Belmans
Department of Electrical Enginering ESAT/ELECTA, KU Leuven
Kasteelpark Arenberg 10 B-3001 Leuven, Belgium
http://www.esat.kuleuven.ac.be/electa/
Summary – The newly introduced distributed or decentralized generation (DG) units connected to local distribution systems are in general not dispatchable by a central operator and can have a significant impact on the power flow, voltage profile, stability, continuity and quality of power supply for customers and electricity suppliers. Due to the locally available resources and the small scale, DG units are mostly connected at the distribution level. When the penetration of DG is high, the generated power of DG units not only alters the power flow in the distribution system, but in the transmission system as well. This paper addresses the influence of distributed generation on the voltage and angle stability of the transmission system. An existing transmission system and different DG technologies at adequate penetration level are modelled using the well-known Eurostag software package. The simulation methodology is discussed as well. The results show that the connection of DG has a significant impact on voltage and angle stability of the system, which depend on the DG generator technology.
C6-205
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C6-206
Summary In accordance with the goals of the European Commission the energy output of dispersed generation is expected to grow by 300 TWh/a until 2010 in the European Community.
The question arises, how a network could be operated with such a large share of mostly intermitting power sources? How can the reserve power be limited which is required for compensation of power fluctuations and ensuring a safe network operation?
In this context, a vision sees the power system of the future consisting of a number of microgrids. In each of these microgrids a significant share of the power demand will be covered by dispersed generation. However, the power balance of the microgrids shall be planable and dispatchable in such a way that the import or export of power from or into the higher level network has to follow a schedule which can be predicted with a high level of accuracy in advance.
The experience of a German pilot project is reported. The targets were defined as the development of:
• methods analyzing the conformity and reliability of large scale dispersed generation in existing networks;
• the dispatchability of microgrids with a significant share of dispersed generation and storage by means of decentralized power generation and load management and the use of the related communication channels in practice;
• experience in practice and definition of the future requirements for the operation of such new technologies like Fuel Cell Cogeneration of Heat and Power, innovative battery storage units or MVDC couplers.
The main result of the investigations is: Dispersed generation has no technical constraints if Conformity, Reliability and Dispatchability can be ensured. It is demonstrated that the dispersed generation, storage and network coupling is able to contribute in the improvement of voltage quality and reliability. Additionally, it offers an economical alternative for network reinforcement. However, ensuring conformity, reliability and dispatchability requires new rules establishing obligations in concern to availability and controllability of the dispersed generation. In the first priority, the legal framework has to be adapted and the communication standard IEC 61850 shall be used to achieve high efficiency in the engineering of the required communication network. Keywords: Distribution - Network – Generation - Storage – Coupling – Planning - Program – Power Quality – Reliability – Energy – Management
ADVANCED PLANNING AND OPERATION OF DISPERSED GENERATION ENSURING POWER QUALITY, SECURITY AND EFFICIENCY IN DISTRIBUTION
SYSTEMS
Germany
B. BUCHHOLZ* C. SCHWAEGERL
Siemens AG
T. STEPHANBLOME
EUS GmbH
H. FREY
EnBW
N. LEWALD
Stadtwerke Karlsruhe
GmbH
Z. STYCZYNSKI
Otto von Guericke Universität Magdeburg
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C6-207
INTEGRATION OF LARGE SCALE WIND POWER IN POWER SYSTEMS: IMPACT ON FREQUENCY CONTROL AND VOLTAGE FLUCTUATION
PEDRO A. C. ROSAS*
POUL SØRENSEN
HENRIK BINDNER
HERIVELTO S. BRONZEADO
CBEE (Brazil)
RISØ (Denmark)
CHESF (Brazil)
Several countries are planning to integrate large-scale wind power in the coming years based on energy policies or environmental issues. In general, those plans are ambitious and intend to install thousands of megawatts of wind power in order to supply a considerable part of the load. One of the main issues with respect to the connection of large scale wind power generation to the bulk system is the impact on the power quality and stability of the electric power system. The main problems of power quality that has been reported associated to wind power generation are voltage fluctuation (which causes flicker), voltage distortion (harmonics), voltage dips and also slow steady-state voltage variation. Other concerns are power system oscillations, load dispatch control, scheduling power generation, transient stability and islanding of part of power systems. In this paper it is analysed the impact of integrating large scale wind power on dynamic power system voltage and frequency control. The methodology proposed can be generalized to be applied to different power systems and wind power conditions. The methodology can be applied to very large power systems and the model of aggregate wind farms results in less computation time been straightforward applied to assess the wind power impact. The simulation results help to understand the dynamic power system interaction with large wind energy penetration. Using modal techniques, the most significant electromechanical modes are normally identified and characterized. Additionally, dynamic simulations using AWF is useful to the analysis as it includes the non linearities. In the case studied the electromechanical modes show to be well damped (frequency controllers well designed) hence the power oscillations caused from the wind power did not increase in time. Using dynamic simulations was also possible to verify the voltage controller’s performances. The simulation results showed that the voltage controllers in Nordel system works properly, compensating dynamically the variable reactive power. The simulation also showed that in the Nordel system the impact of 4,400 MW of wind power is very small even though some electromechanical modes has been excited this is should be due to the stiffness of the Nordel system.
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C6-301
RURAL ELECTRIFICATION IN DEVELOPING COUNTRIES WITH THE SHIELD WIRE SCHEME. APPLICATIONS IN LAOS
F. Iliceto∗), F.M. Gatta, P. Masato
University of Rome “La Sapienza” Rome, Italy
H. Sysoulath Electricité du Laos
Vientiane, Laos SUMMARY Firstly, the paper briefly describes the technique for 3-phase and single-phase power distribution along HV (115-330kV) transmission lines via the insulated shield wires, energized at MV (20-34.5kV) from the main HV/MV transformer stations, using the ground as a MV phase conductor. A new computer program based on phase coordinates is presented, expressly developed for the analysis of this unconventional low cost grid based electrification technique, referred as the “Shield Wire Scheme” (SWS). SWSs allow electricity to be made available at MV to communities located along the HV transmission lines, with an installation cost that is only 10-15% of cost of independent MV lines on the same right of way. Environmental impact and maintenance costs of Shield Wire Lines (SWLs) are negligible.
14 years of operational experience in Ghana has confirmed the viability of the “3-Phase” SWSs, which provide a quality of service to consumers not inferior to the one of equivalent conventional MV lines. On the basis of this field experience, Electricité du Laos firstly implemented three “Single-Phase Earth-Return” SWSs and has recently commissioned five “3-Phase” SWSs serving a large rural population.
The paper describes the SWSs in operation in Laos. In particular, the planning and main engineering criteria are reported for five “3-Phase” SWSs, put into operation in 2002-3 and providing electricity to over 100 villages, to some small towns and to a provincial capital, located along over 300 km of 34.5 kV SWLs and 100 km of 34.5 kV lateral lines (extensions to communities located at some distance from the HV line route). Loading capability of a 34.5 kV, 100 km long SWL is up to 5000 kW. Measurements during commissioning and the initial operation of “3-Phase” SWSs in Laos have provided the following results:
• Phase-to-neutral voltages at the LV terminals of MV/LV transformers are in the range from 220 to 230 V.
• Negative sequence voltage is ≤ 0.5 % (it is calculated to be ≤ 1 % when full design load will be reached).
• Step and touch voltages of grounding systems for earth return of current are generally ≤ 7 V. • Faults on SWLs are only of transient nature, caused almost solely by lightning. Fault rate is lower
than in conventional MV lines of same length and voltage. • Lightning performance of HV circuits is practically not affected by the insulation of shield wires
for MV. Brief information is given on SWSs in operation, under construction and planned in other developing countries.
∗) Dept. of Electrical Engineering, Via Eudossiana 18, 00184 - Roma, Italy
e-mail: [email protected]
______________________________________________________ [email protected]
C6-302
Cost effective electrification in South Africa: Load Matching and Technical Developments.
HJ Geldenhuys*, CT Gaunt#, R Stephen@
* Eskom Distribution, South Africa # University of Cape Town, South Africa @ Eskom Enterprises, South Africa
Synopsis
This paper outlines how Eskom has improved its rural electrification technology, largely by using single-phase MV lines combined with single- and dual-phase LV feeders to match the feeder transfer capability to the load. From 1994 to 2003 Eskom has reduced the cost of electrification connections by about 50% in real terms. KEY WORDS: Electrification, Medium Voltage, Reticulation, Electricity Distribution, Rural Electrification.