Showing papers presented at "International Conference on European Electricity Market in 2008"

On the use of energy storage technologies for regulation services in electric power systems with significant penetration of wind energy

Abstract: Energy produced by intermittent renewable resources is sharply increasing in the United States. At high penetration levels, volatility of wind power production could cause additional problems for the power system balancing functions such as regulation. This paper reports some partial results of a project work, recently conducted by the Pacific Northwest National Laboratory (PNNL) for Bonneville Power Administration (BPA). The project proposes to mitigate additional intermittency with the help of Wide Area Energy Management System (WAEMS) that would provide a two-way simultaneous regulation service for the BPA and California ISO systems by using a large energy storage facility. The paper evaluates several utility-scale energy storage technology options for their usage as regulation resources. The regulation service requires a participating resource to quickly vary its power output following the rapidly and frequently changing regulation signal. Several energy storage options have been analyzed based on thirteen selection criteria. The evaluation process resulted in the selection of flywheels, pumped hydro electric power (or conventional hydro electric power) plant and sodium sulfur or nickel cadmium batteries as candidate technologies for the WAEMS project. A cost benefit analysis should be conducted to narrow the choice to one technology.

Harmonic impact of small photovoltaic systems connected to the LV distribution network

Abstract: Since the penetration of photovoltaic (PV) systems in the low voltage (LV) distribution network is increasing, the need to register and model the contribution of these systems to the harmonic distortion of current and voltage waveforms is becoming an up-to-date issue. As PV systems incorporate power conditioning units, which are harmonic generating devices, they will have an influence on quality of supply, reliable operation of system equipment as well as component life expectancy. This paper investigates the harmonic impact of a 20 kWp PV system connected to the LV distribution network in Greece. The harmonic behavior of the PV plant as a function of the solar radiation under several weather conditions is analyzed. Measurements results are compared to those obtained from the power simulator package PSIMcopy. The level of penetration of PV systems in the LV distribution network without harmonic limits been exceeded is investigated.

Multi-area load frequency control in a deregulated power system using optimal output feedback method

Abstract: In this paper, the dynamical response of the load-frequency control problem in the deregulated environment is improved with a pragmatic viewpoint. In the practical environment, access to all of the state variables of system is limited and measuring all of them is also impossible. To solve this problem, in this paper the optimal output feedback method is proposed. In the output feedback method, only the measurable state variables within each control area is required to use for feedback. The optimal control law is determined by minimizing a performance index under the output feedback conditions leading to a coupled matrix equation. The proposed method is tested on a two-area power system with different contracted scenarios. The results of the proposed controller are compared with the full-state feedback method. The results are shown that when the power demands changed, the output feedback method have a good ability to tracking of contracted and/or non-contracted demands. In fact, this method provides a control system that satisfied the load frequency control requirements and with a reasonable dynamic response.

Impact of distributed generation on distribution networks

Abstract: As a consequence of the growing importance of distributed generation (DG) it's very important to study the distribution network behavior. In this paper, voltage profile and gradient are analyzed taking in account power in-feed/out-feed of DG. The influence of reactive power requirements on the network voltage levels, based in the comparison of software simulation results with real-life behavior, are also studied. This paper equally analyzes the impact of DG on the substation transformers taps changers, with and without DG. Finally, it's analyzed the impact of DG on protection systems functioning in a 60 kV network.

Low voltage fault ride through criteria for grid connection of wind turbine generators

Abstract: This paper deals with the performance of grid-connected wind-turbine generators in case of system faults, i.e. short-circuits, the so-called low-voltage-fault-ride-through-conditions (LVFRT-conditions). Furthermore the requirements of frequency, voltage and reactive power control are explained. The conditions are defined in the grid-codes of the utilities even in Europe in a different way, leading to contra dictionary operating conditions in the interconnected UCTE-system. The increasing importance of electricity generation by wind turbines in the future requires similar and standardized operating criteria for all countries.

Simulation of two-area AGC system in a competitive environment using reduced-order observer method

Abstract: In this paper, a reduced-order observer controller is proposed to solve the automatic generation control problem in a deregulated power system that operates under deregulation based on the bilateral policy scheme. In the practical environment (real world), access to all of the state variables of system is limited and measuring all of them is also impossible. So when we have fewer sensors available than the number of states or it may be undesirable, expensive, or impossible to directly measure all of the states, using a reduced-order observer is proposed. A proposed design, which is presented in this paper, has been developed in order to over-come this problem. The proposed strategy is tested on a two-area power system and compared with the optimal full-state feedback method by means of simulation. The results are shown that this method improved the dynamic response of system and provides a control system that satisfied the load frequency control requirements.

Harmonic current emission of photovoltaic installations under system conditions

Abstract: Harmonic currents of PV-inverters show a significant dependency on the harmonic voltage content of the AC-system voltage. Measurements of harmonic currents were carried out in LV-systems and under laboratory test conditions with adjustable harmonic content of the AV-voltage. Two PV-inverters, one with coupling transformer and one without transformer were tested. The results indicated that the emitted harmonic currents depend strongly on the harmonic voltages prevailing in the AC-voltage. PV-inverters without transformer show significant lower harmonic currents than inverters with coupling transformer. The standard test conditions as defined in international standards does not consider real system conditions with respect to the harmonic voltages in system voltage. The measured currents as documented in data sheets are therefore comparatively lower than under the condition of real system operation.

Electricity consumption and economic growth in the European Union: A causality study using panel unit root and cointegration analysis

Abstract: The climate change discussion and rising energy prices have resulted in an increase in the literature on the causal relationship between energy use and economic growth. In addition, there are also new developments in econometrics, most of all the use of panel unit root and cointegration techniques. However those techniques have not been applied in comparative studies covering the European electricity markets so far. The empirical investigation of the causality relationship between electricity demand and income for 15 European countries between 1978 and 2005 involves three steps. First, the order of integration is determined by applying standard ADF and panel unit root testing procedures. Second, cointegration techniques are performed in order to test for the long-run relationship between the variables in question. Finally, the existence and direction of causality in the short- and long-run will be assessed for each country by using vector error correction models and Granger causality tests.

New large-scale security constrained optimal power flow program using a new interior point algorithm

Abstract: This paper presents the main features and the use of the security constrained optimal power flow program, called IPSO (Integrated Power System Optimizer), in the electricity market environment. The finding of the optimal power flow solution is realized with the KNITRO solver developed at Ziena Optimization, Inc. The paper emphasizes the original features of IPSO software such as security constrained modeling in both preventive and corrective strategy, the discrete variables modeling, the modeling of units' capability curves, the modeling of the primary active power-frequency control as well as the modeling of the primary active power-frequency control. Finally, is presented the utilization of the SCOPF program to evaluate the steady state TTC (Total Transfer Capability).

The energy balance of the photovoltaic tracking systems using virtual prototyping platform

Abstract: The paper presents a solution for increasing the energetic efficiency of the photovoltaic systems by using mechanical tracking systems. The key idea is to maximize the energy gained through orientation, and to minimize the energy consumption for tracking of the Sun path. The optimization is made by reducing the angular revolution field of the panel, and consequently the operating time of the motor, without significantly affecting the incident radiation. In fact, we are looking for the optimal angular field in which the panel absorbs as much as possible solar radiation with minimum energy consumption. The application is made for a polar tracking system, by using a virtual prototyping platform that contains specific software solutions, in the concurrent engineering concept, as follows: CATIA - for developing the geometric model of the tracking mechanism, ADAMS/View - for analyzing & optimizing the tracking system, and MATLAB/Simulink & ADAMS/Controls - for developing the control system.

Power exchange price volatility analysis after one year of Trilateral Market Coupling

Abstract: Trilateral market coupling (TLC) was launched in November 2006 in Belgium, France and the Netherlands. The initiative results in a sharp decrease of hourly price differences. This paper analyses whether the price convergence obtained, also reduced price volatility. Evidence for a significant price volatility reduction has only been found on APX. One possible explanation is given by introducing the volatility reduction potential based on the non-simultaneous occurrence of shocks.

Active grid integration of distributed generation utilizing existing infrastructure more efficiently - an Austrian case study

Abstract: This paper presents the technical and economical results for an Austrian case study for grid integration of distributed generation (DG). The current state of the grid segment is shown and its inability to host higher than present amounts of DG is discussed. Consequently, technical solutions to overcome this problem without reinforcing the grid are presented. Different strategies of active voltage control are studied on the basis of extensive simulations using the DIgSILENT PowerFactoryreg software. Detailed economic analyses for different grid segments as well as producer-driven strategies (e.g. local or coordinated voltage control) for voltage control are performed. These approaches are furthermore compared to conventional grid reinforcement measures, showing that investments in new smart grid technologies may even lead to lower overall cost for society.

Virtual power producers market strategies

Abstract: This paper presents MASCEM - a multi-agent based electricity market simulator. MASCEM uses game theory, machine learning techniques, scenario analysis and optimisation techniques to model market agents and to provide them with decision-support.

Evaluation of energy storage devices for renewable energies integration: Application to a Portuguese wind farm

Abstract: This paper evaluates the benefits of energy storage systems applied to renewable intermittent sources like wind. With this objective, a 144 MW Portuguese wind farm is used as a case-study. The storage system design and evaluation processes use a computational tool developed in MatLab to simulate the wind farm operation with an energy storage system and computes the remuneration tariff. The energy storage design settles on a system of 5 MW with 30 MWh. The simulation results show a 2.1% gain in wind farm tariff and a improved adjustment on generation to the typical electricity demand curve. Considering the storage system design and an available storage technology survey, one concludes that redox flow batteries are the best suited to application, in spite of their present prices being not the most advantage.

A model for electricity markets: The impact of regulation on value

Abstract: In this paper it is proposed a simple, although useful model, intended for electricity markets, which enlightens the analysis of regulatory procedures and their consequences over value creation. Today it is widely recognized that, in regard to public services, the aim of regulation should be to maximize the social wealth added (EWA). This wealth includes consumers surplus (ECA), tributes paid to government (EGA) and investor value added (EVA). Thus, regulation implies both efficiency, regarding the location of resources, and fair price levels. The task is seriously impaired by informational asymmetries, and a second-best optimum is only attained with incentive-compatible contracts. Those problems, among many others, can be treated with the proposed model. In order to clarify some of the issues, an example is developed showing the social wealth added under several instances of market operation: regulates vs. unregulated firm, level of taxation, and optimized vs. non-optimized investment and resources.

Modeling hydro power plants in deregulated electricity markets: Integration and application of EMCAS and VALORAGUA

Abstract: In this paper, we present details of integrating an agent-based model, Electricity Market Complex Adaptive System (EMCAS) with a hydro-thermal coordination model, VALORAGUA. EMCAS provides a framework for simulating deregulated markets with flexible regulatory structure along with bidding strategies for supply offers and demand bids. VALORAGUA provides longer-term operation plans by optimizing hydro and thermal power plant operation for the entire year. In addition, EMCAS uses the price forecasts and weekly hydro schedules from VALORAGUA to provide intra-week hydro plant optimization for hourly supply offers. The integrated model is then applied to the Iberian electricity market which includes about 111 thermal plants and 38 hydro power plants. We then analyze the impact of hydro plant supply offers on the market prices and ways to minimize the Gencospsila exposure to price risk.

Multinational electricity market integration and electricity price dynamics

Abstract: The paper empirically explores the electricity price dynamics in the Nordic power market, Nord Pool, during the years 1996-2006 Empirically the study reveals that the conditional mean electricity price increased when Finland joined, and remained at the higher level when Denmark also joined Turning to the price volatility, this increased when Finland joined, but decreased when Denmark also joined However, the price jump-intensity decreased both when Finland and Denmark joined the market This means that a larger electricity market seems to reduce the probability of sudden price jumps That is, the multinational electricity market integration seems to have created a market that handles external shocks to supply and demand more efficient than the separate national electricity markets previously did

Micro generation — Solar and wind hybrid system

Abstract: Energy faults will cause strong problems and damages in nowadays daily life. Without energy, industry will stop and also the fundamental goods would be inaccessible, mainly in the big cities. In this work, a hybrid system with solar energy and wind energy production is proposed. The main aspects of the system are described and shown. Also the economical aspects are referred.

An economic analysis of a power production hybrid system

Abstract: This paper analyses the economic viability of a power production hybrid system (photovoltaic-wind-fuel) for domestic supply in isolated areas. A correctly designed photovoltaic-wind-diesel hybrid system enlarges considerably both the diesel generator lifecycle as well as the batteries lifecycle, when referring to the most common used technology (off-grid generator systems). Both benefits need to be correctly accounted in the evaluation process, as maintenance costs are reduced significantly in the case of a PV-wind-diesel solution. This paper aims to develop a new method to evaluate the design of a PV-wind-diesel hybrid system for electricity production. The different types of renewable sources are specifically evaluated in the economical performance of the overall equipment. The developed methodology bases the investment decision on the standard net present value analysis, with sound capital cost evaluation.

Energy systems analysis of CCS development in Europe

Abstract: The paper presents policy analysis regarding the prospects of carbon capture and storage (CCS) in the energy system of the European Union (EU) up to 2030. The analysis follows a systemic approach, investigating a series of alternative scenarios using the large scale energy systems model PRIMES for all member states (MS) of the EU. Measures supporting the European environmental and energy policy were combined with policies concerning the promotion of the technology in order to identify the economic and environmental implications and the rate of deployment of CCS in the European energy system.

Day-ahead electricity price forecasting using the relief algorithm and neural networks

Abstract: In a competitive electricity market, forecast of energy prices is a key information for the market participants. However, price signal usually has a complex behavior due to its nonlinearity, nonstationarity, and time variancy. In spite of all performed researches on this area in the recent years, there is still an essential need for more accurate and robust price forecast methods. In this paper, a combination of a feature selection technique and neural network (NN) is proposed for this purpose. The feature selection method is a modified version of the relief algorithm, proposed for the feature selection of price forecasting. Then, by means of the most relevant, explanatory and irredundant features, a neural network (NN) predicts the next values of the price signal. The adjustable parameters of the whole method are fine-tuned by a cross-validation technique. The proposed method is examined on PJM electricity market, forecasting day-ahead locational marginal prices (LMPs), and compared with some of the most recent price forecast methods especially some other popular and validated feature selection techniques. These comparisons indicate the validity and robustness of the proposed forecasting method.

Influence of power transformer winding connections on the propagation of voltage sags through electric system

Abstract: This paper addresses several important issues for reliable assessment of the number of voltage sags in modern distribution systems. Depending on the conditions of the network voltage sags propagate differently and affect different areas of the network. The analysis has been carried out to assess the influence of network topology on voltage sag propagation. The purpose of this paper is to analyze the influence of all types of connections transformers on the propagation of voltage sags on electrical system. The study shows that some transformer winding connections like Yd have more significant influence than any other type of winding connection. For analyzes the phenomenon, it was modeled on the ATP - alternative transient program - a standard IEEE 14-bus system and a sags generator, which is able to generate any kind of voltage sag with any variations of the magnitude and phase angle. With mathematical formulations based on balanced and unbalanced circuits theories.

On allocation of the transmission network losses using game theory

Abstract: One of key elements of liberalized markets being faced by consumer is a transparent cost structure of electricity supply. Part of this cost corresponds to the coverage of losses in the network. Several approaches to loss allocation exist, most commonly such as, charging in proportion to consumed energy or location marginal pricing. The first method fails to accurately link the consumption with the cause of losses. The second approach tends to be very sensitive to the change of parameters of the problem. Therefore, they do not fully satisfy criteria imposed on an allocation method: transparency and fairness. According to game theory, a fair and a transparent allocation of cost can be achieved using a concept of Shapley value. This paper presents a methodology and studies some properties of loss allocation mechanism using Shapley value.

Impacts of integration of wind generation on regulation and load following requirements of California power systems

Abstract: This paper describes a methodology to evaluate the amount of required regulation and load following capability to maintain reliability in the CAISO Control Area. The methodology is based on a mathematical model of the CAISOpsilas actual scheduling, real-time dispatch and regulation processes. The forecast load and wind power are stochastic quantities, represented by two series of minute by minute values: the load/wind-power average value and its standard deviation magnitude. The hour-ahead wind generation forecast was assumed to be a part of the future CAISO/scheduling coordinator (SC) scheduling system. CAISO actual 2006 data and simulated 2010 data are analyzed by season. Load following and regulation requirements, including the capacity, ramping, and duration requirements by operating hour within a season of 2006 and 2010 were analyzed simultaneously.

Long-term planning of natural gas networks

Abstract: Due to the forthcoming regulation schemes throughout Europe, new challenges for natural gas network operators arise. The pressure for realising and operating cost-efficient network structures increases as the regulation is based on comparison between network operators and the tolerable costs are set by the network operator with minimal costs. Computer-based optimisation methods, which will also be applied by Regulatory Authorities as part of the analytical cost models for calculating the efficiency of electricity and natural gas networks, provide the opportunity to identify long-term cost-efficient network structures, so called reference networks. Boundary conditions of natural gas networks, which concern the systempsilas technical safety and thus need to be regarded during network planning, are given by the rules set of each countrypsilas technical association for natural gas supply. Degrees of freedom for the optimisation are given by the choice of different network structures, the number and operating pressure of pressure stages and for the dimensioning of equipment. Therefore, computer-based optimisation methods are required for solving the extensive optimisation problem. An optimisation method for natural gas distribution networks based on Genetic Algorithms is proposed. The method is capable of calculating cost-efficient network structures with regard to all technical and economical boundary conditions and is also used by the German Federal Network Agency for calculating reference networks with minimum costs for given supply tasks. Exemplary results demonstrate the methodpsilas capability and the advantages given by the application of this method on long-term planning of natural gas networks.

Assessment of the actions to reduce CO 2 emissions in the Italian power system

Abstract: Aim of the paper is to assess, by means of a scenario analysis, the effectiveness and costs of different actions to reduce CO2 emissions in the Italian power system, i.e. increase of the efficiency of both fossil and renewable generation technologies, use of carbon capture and storage technologies, development of renewable energy sources through the implementation of incentive schemes and increase of the efficiency in electricity end-uses. The study shows that all the actions taken into account are not sufficient to achieve the CO2 emissions target hypothesized for 2020. Only high penalties on CO2 emissions, such as the ones deriving from the application of an additional carbon tax, causing a complete switch from coal to gas (with a consequent hardly acceptable dependency on natural gas), could reduce the distance from the target to an amount that could reasonably be covered by the Kyoto protocol flexible mechanisms.

Time-frequency transforms comparison for power quality analysis

Abstract: Voltage signal contains transient disturbances that are caused for multiple reasons. One way to improve the power quality is to analyze efficiently and to deeply understand these signals. The most typical disturbances in power quality have been generated in order to analyze by time-frequency transforms: wavelet transforms (WT) and S-transform (ST). Thus can be obtained a comparison of results of these time-frequency transforms. The voltage signals with different disturbances are simulated by Matlab code with 128 samples per cycle. The disturbances used in this work are carried out from standards, as voltage sag, voltage swell, short interruptions and harmonic distortion, in addition to other disturbances of transitory order as spikes, notches and oscillatory transients.

An algorithm for the decentralized market coupling problem

Abstract: In this communication a conceptual algorithm is proposed for the market coupling process in the presence of block orders. The basic idea is to use the Lagrangian relaxation to get a decomposition of the problem that emulates the necessary decentralization process. The feasibility of this procedure is analysed using a simplified model of the problem. In particular, the solution obtained in this decentralized way is contrasted with the numerically exact solution of the problem by evaluating the duality gap. The examples presented suggest that in this way reasonably approximate solutions can be obtained, to improve those obtained through empirical procedures used by the market operators.

European electricity and emission market modeling — the design of emission allocation plans and its effects on investment planning

Abstract: The introduction of emissions trading and the design of allocation plans have far-reaching implications on the development of the power plant mix, the CO2-emissions, and the power plant investments of energy utilities Especially CO2- and electricity prices as well as the design of the allocation rules get more and more important for investment strategies of energy utilities For this reason it is necessary to analyse the impacts of the Emission Trading Scheme on the future of power generation and investment decisions in power industry For this purpose this paper shows some possibilities to analyse the impact of different allocation methods by using optimizing energy system models Results show that the emission allocation scheme has a significant influence on power generation planning and power plant investments and with this on the evolution of CO2-emission and electricity market

A combination method for short term load forecasting used in Iran electricity market by NeuroFuzzy, Bayesian and finding similar days methods

Abstract: Short term load forecasting (STLF) plays an important role for the power system operational planners and also most of the participants in the nowadays electricity markets. With the importance of the STLF in power system operation and electricity markets, many methods for arriving careful results, are represented. In this paper, a combination approach for STLF is proposed. The proposed approach is based on the weighted method for STLF results from Bayesian neural network, neurofuzzy and finding similar days methods. According to the obtained research, these 3 mentioned methods have the best results for the STLF of Iran national power system. Because Iran calendar is a combination of two solar and lunar calendars, so the special conditions, such as: solar and lunar holidays, days after or between holidays have the variable results with these 3 methods. For arriving STLF careful results, the least square method is used for combining these 3 methods. By using this technique, the effect of improper results is ignored. The results for Iran power system, shows that the idea can improve the performance of the STLF.