Electric industries, Production scheduling, Contract method, Decision making, Letting of contracts, Simulation methods & models, Probability theory, Marketing, and Electricity
Abstract
The electric power industry is confronted with a major restructuring in which operation scheduling is decided based on a competitive market. In this new arrangement, bidding strategy becomes an important issue. Participants of the deregulated energy marketplace may be able to compete better by choosing a suitable bidding strategy for trading electricity. In such a deregulated market, coalition formation with other participants may change the diffusion of profit. Therefore the problem changes to the selection of the best participant for coalition and joint bidding strategies. Different classic methods for decision making in the uncertain environment of the market can be applied to select a suitable strategy. Most of these methods, such as game theory that insures reaching the optimal solution for all market participants, require a lot of information about other market players and the market. However, in a real marketplace only a little information such as the spot price is available for all participants. A modified reinforcement-learning approach based on Q-adjusted annealing has been applied to determine the optimal strategy for a power supplier in an electricity market with multiple sources. A modified IEEE 30-bus system has been considered and the simulation results are shown to be the same as with standard game theory. The main advantage of the proposed method is that no information about other participants is required. Investigation shows that if all participants use this method they will stay in Nash equilibrium. [ABSTRACT FROM AUTHOR]
Purchasing, Prices, Market volatility, Cost control, Consumers, and Electricity
Abstract
A solution technique is formulated and provided for the electricity procurement problem faced by a large consumer. The objective of this consumer is to minimise procurement cost while limiting the risk of cost fluctuation due to pool price volatility. Electricity sources include the pool, bilateral contracts and self-production. Uncertainty is related to electricity pool prices. A realistic case study is analysed and results presented. Conclusions are duly drawn. [ABSTRACT FROM AUTHOR]
Market equilibrium, Electric industries, Electricity, Electric power transmission, and Electric power systems
Abstract
Electricity markets with only a few large suppliers often exhibit less competitive behaviour than desired. The presence of transmission constraints further restrict competition among suppliers and provide more opportunities for suppliers to exercise market power. While it is generally acknowledged that long-term contracts provide good measures for mitigating market power in the spot market, thus reducing undesired price spikes, it is not clear how effective these contracts are if the market is severely limited due to transmission constraints. An analytical approach through finding a Nash equilibrium is presented for studying the effects of long-term contracts on market equilibrium in a bid-based pool with transmission constraints. Surprisingly the analysis shows that the presence of long-term contracts may result in reduced expected social welfare. [ABSTRACT FROM AUTHOR]
Markets, Electric power distribution, Stochastic models, Electric utilities, Electricity, and Energy demand management
Abstract
Wholesale electricity markets can be organised into different types of markets—energy markets and ancillary services markets—that are cleared sequentially. The paper proposes a stochastic-optimisation model to obtain the distribution of the electricity resources of a generation firm among the different sequential markets within a wholesale electricity market. Market power is modelled by linear approximations of the residual-demand curves. In addition, the model obtains the bid curves of a generation firm that are submitted for every hourly period of each market comprising the sequence. A methodology to estimate the stochastic residual-demand curves for every hour of each market based on decision trees has been designed. The model has been developed for a Spanish utility to operate in the Spanish electricity market. A case study illustrates the performance of the proposed model. [ABSTRACT FROM AUTHOR]
Electric industries, Electricity, Electric lines, and Electron tube grids
Abstract
The worldwide trend for the deregulation of the electricity generation and transmission industries has led to dramatic changes in system operation and planning procedures. The optimum approach to transmission-expansion planning in a deregulated environment is an open problem especially when the responsibilities of the organisations carrying out the planning work need to be addressed. To date there is a consensus that the system operator and network manager perform the expansion planning work in a centralised way. However, with an increasing input from the electricity market, the objectives, constraints and approaches toward transmission planning should be carefully designed to ensure system reliability as well as meeting the market requirements. A market-oriented approach for transmission planning in a deregulated environment is proposed. Case studies using the IEEE 14-bus system and the Australian national electricity market grid are performed. In addition, the proposed method is compared with a traditional planning method to further verify its effectiveness. [ABSTRACT FROM AUTHOR]
Risk assessment, Finance, Stochastic analysis, Prices, Direct costing, Electricity, and Electric generators
Abstract
There is a high level of financial risk associated with the direct participation of wind generation in liberalised electricity markets, due to the stochastic nature of output and imbalance charges set by market prices. The positioning of generation with respect to the market is therefore critical to successful trading activities. Examined is the use of risk characterisation to select the best output level for a wind generator to trade, dependant on maximising revenue and managing marginal costs from imbalances in a competitive market situation. Trading strategies based on utility risk assessment are presented as a possible way to improve market participation for wind generators based on these criteria. [ABSTRACT FROM AUTHOR]
Electric utilities, Electric industries, Electric rates, Electric power distribution, Power resources, Electricity, Magnetism, and Electric power
Abstract
The battle for electricity customers in an increasingly competitive and deregulated market environment is one of the challenges facing the electric power utilities of today. Customers expect a reliable and efficient supply of power from their utilities. One of the advantages that a distributed generator (DG) can provide to the electric utility and to customers is the possibility of improving the continuity of supply by implementing safe intentional islands in the event of upstream utility supply outage. Implementing intentional islanding of DG in a deregulated era will have an impact on electricity market prices. This problem is considered in this paper by solving the optimal power flow problem while accounting for islanded operation. [ABSTRACT FROM AUTHOR]
Box-Jenkins forecasting, Statistical hypothesis testing, Investment analysis, Estimation theory, Probability theory, Electricity, Magnetism, and Confidence intervals
Abstract
Accurate electricity price forecasting is a crucial issue concerned by market participants either for developing bidding strategies or for making investment decisions. Due to the complicated factors affecting electricity prices, accurate price forecasting turns out to be very difficult. The autoregressive integrated moving average (ARIMA) approach has been extended to make hourly market clearing price (MCP) forecasting in electricity spot markets with error correction and confidence interval estimation. The ARIMA model used for forecasting price and the method to implement price forecasting are presented first. Then the ARIMA approach is extended to include error correction for improving accuracy of price forecasting. Moreover, the confidence interval of the forecasted prices is estimated assuming the residual errors are in gaussian or uniform distribution. Hourly MCP forecasting of the Californian Power Market is used as a computer example, and the comparison with conventional ARIMA approach is given. Computer test results show clearly that the suggested extended ARIMA approach for spot price forecasting is very effective with satisfactory accuracy. It can work under very worse market conditions with high price volatility. [ABSTRACT FROM AUTHOR]
Industrial organization (Economic theory), Dynamic programming, Probability theory, Monte Carlo method, Electricity, Electric generators, and Equilibrium
Abstract
Electricity markets based on power pools, in which the owners of generating units submit their marginal-price schedules, implicitly leave the problem of unit commitment and its associated constraints and costs aside. The paper addresses the unit-commitment problem faced by participants if they are to self-commit their units in a market structure. This strategic problem is formulated through a probabilistic-dynamic-programming model, where the probability of a particular generator being online during a specific market period is set by its owner. The solutions adopted for that problem are Nash equilibria in mixed strategies. The paper presents an example with a small group of generating units, where a comparison is made between the results for the integrated utility and for the market structure. This example is solved making use of a direct Monte Carlo method. [ABSTRACT FROM AUTHOR]
Electricity, Power transmission, Graph theory, Electric generators, and Electrical load
Abstract
In a competitive-market environment, deregulation of the electricity industry and thus transmission open access make it even more important to allocate the cost of transmission service fairly. The proposed method can deal with the problem of reactive-power decomposition which could not easily be resolved previously. An equivalent line circuit based on the nominal-T model for reactive-power decomposition is presented. Graph theory and the proportional-sharing principle are employed to trace power flow; the results are then employed to determine the real-power contribution of generators to lines and loads and the reactive-power contribution of generators and lines to loads. The proposed method is illustrated by means of a simple example. Because complex power rather than real power is considered, numerical results from the proposed method are more reasonable than those from the method which considers only real power. [ABSTRACT FROM AUTHOR]
Electric utilities, Electric power system control, Electric power system stability, Voltage regulators, and Electricity
Abstract
Within the competitive framework of the electricity industry, there is a need for tools to assess both the current and short-term operating conditions. A metric consisting of a global index used as an alert device to decide on resource mix modifications, based on a quantitative assessment of the dynamic performance of the power system, is developed and applied. The proposed metric includes a set of indices to evaluate both the system's steady-state operating condition and the three main dynamic aspects of system stability: transient or angular stability, frequency stability and voltage stability. These indices are weighted according to the security and quality levels required by regulatory policies. Based on the value of the global index, control actions are established and economically evaluated according to a cost–benefit analysis for improving the dynamic performance of the system. The metric is applied to one of Chile's interconnected grid systems in five different operating scenarios. [ABSTRACT FROM AUTHOR]
Markets, Prices, Electric industries, Electricity, and Electric power systems
Abstract
Achieving higher system reliability using market-based approaches is a contemporary issue that has been attracting a great deal of attention in the emerging deregulated electricity-market structure. The paper presents a methodology for the modelling and evaluation of interruptible-load programmes to tackle this issue. The interruptible-load programme is formulated as an equivalent price-based generating resource with a random outage effect, and is thus incorporated in a probabilistic production simulation of a system. The interdependence between the electricity spot-market price and the equivalent generating-resource parameters is addressed and solved by an iterative co-ordinating algorithm. The proposed approach is capable of achieving comprehensive evaluations and systematic decision making for the interruptible load programme in electricity-market operation. A numerical-case-study example is presented to illustrate the validity of the method. The results reveal that interruptible-load programmes can serve effectively as a market-based tool to achieve a proper balance between generation-capacity reliability and economics in the competitive electricity markets. [ABSTRACT FROM AUTHOR]
Pricing, Marginal pricing, Bid price, Electricity, and Numerical analysis
Abstract
The existence of undesirable electricity price spikes in a competitive electricity market requires an efficient auction mechanism. However, many of the existing auction mechanism have difficulties in suppressing such unreasonable price spikes effectively. A new auction mechanism is proposed to suppress effectively unreasonable price spikes in a competitive electricity market. It optimally combines system marginal price auction and pay as bid auction mechanisms. A threshold value is determined to activate the switching between the marginal price auction and the proposed composite auction. Basically when the system marginal price is higher than the threshold value, the composite auction for high price electricity market is activated. The winning electricity sellers will sell their electricity at the system marginal price or their own bid prices, depending on their rights of being paid at the system marginal price and their offers 'impact on suppressing undesirable price spikes. Such economic stimuli discourage sellers from practising economic and physical withholdings. Multiple price caps are proposed to regulate strong market power. We also compare other auction mechanisms to highlight the characteristics of the proposed one. Numerical simulation using the proposed auction mechanism is given to illustrate the procedure of this new auction mechanism. [ABSTRACT FROM AUTHOR]
Finite element method, Simulation methods & models, Electric impedance, Electricity, and Underground electric lines
Abstract
The lossy earth return path influences significantly the impedances of underground power cables, especially in cases where transient simulation models are of interest. The use of approximations for the calculation of the earth correction terms proves to be inaccurate, especially at high frequencies or for low earth resistivities. A novel direct numerical integration scheme for the evaluation of the infinite integral terms is presented. The new method proves to be numerically stable and efficient in all cases examined. Results obtained by the novel integration scheme are compared with those obtained by other approaches, as well as by a finite-element method formulation for several single-core cable configurations and for cases of homogeneous and multilayered earth. [ABSTRACT FROM AUTHOR]
Voltage regulators, Electric controllers, Newton-Raphson method, Iterative methods (Mathematics), and Electricity
Abstract
This paper presents an efficient method for the formation of voltage control areas. The proposed method considers the effect of P-V and Q-δ coupling and changes in network topology. The full Newton Raphson load flow (NRLF) Jacobian sensitivities and voltage variations under contingencies have been used for the formation of the voltage control areas. These areas have been reduced to equivalent nodes using the REI reduction technique, and the reduced network has been validated for the voltage stability analysis. The effectiveness of the method has been established on the IEEE 14-bus system and a practical 75-bus Indian system. [ABSTRACT FROM AUTHOR]
Thyristors, Electric current rectifiers, Reactance (Electricity), Alternating currents, and Electricity
Abstract
A single-phase static VAR compensator (SVC) is proposed to regulate smoothly the output voltage of a single-phase self-excited induction generator (single-phase SEIG) driven by a variable-speed prime mover (VSPM) due to inductive load and prime mover speed variations. A PI feedback closed-loop voltage regulation scheme is presented to adjust the equivalent excitation capacitance of the single-phase SVC. The SVC is composed of a fixed excitation capacitor (FC), thyristor switched capacitor (TSC) and thyristor controlled reactor (TCR). The steady-state single-phase SEIG output voltage and the TCR triggering angle responses of the proposed scheme are simply evaluated and discussed. A small-scale single-phase SEIG voltage control prototype is designed in order to verify system viability and assess its performance. System dynamic operation is studied based on experimental results. Simulation and experimental results prove system practical effectiveness in terms of fast response and high performance. [ABSTRACT FROM AUTHOR]
Algorithms, Capacitance meters, Electric capacity, Electric impedance, and Electricity
Abstract
An approach to numeric distance relaying is proposed that is suitable for EHV composite overhead line and underground cable circuit applications. The proposed relay incorporates a circuit shunt capacitance in addition to a series resistance and inductance. By modelling the protected circuit as a series of RLC sections within the relaying algorithm, greater reach point accuracy can be achieved. Unlike conventional distance relays that sense the fault loop impedance and compare this against a reach point value, the proposed relay uses a directional element that is based on the calculated reach point voltage and current values. Results are presented based on a composite 500 kV application study comprising two overhead line sections and two cable sections. Comparisons with conventional numeric distance relay algorithms show that overreach is virtually eliminated in the proposed relay. The simulation results have been verified with an implementation of the relay based on modern digital signal processing hardware. [ABSTRACT FROM AUTHOR]
Algorithms, Electric impedance, Electricity, Electric networks, and Electric network topology
Abstract
A method to detect and locate a high-impedance fault caused by a downed conductor on a distribution primary feeder cone is presented. The protection system in radial networks generally consists in placing current detectors along each feeder lenz. A down-conductor fault typically has a very low current values which is often not detectable by conventional overcurrent protection devices. The proposed method is not based on current measurement but instead on voltage measurements performed at MV/LV stations. This method may be particularly interesting if LV potential transformers are already present in the network. The method is divided into two steps. The first step consists in determining whether each sensor is above or below the fault. The second step consists in determining the fault section, from a purely topological method. EMTP simulations are presented to highlight the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]
Pricing, Methodology, Electricity, Interconnected power systems, and Electric power systems
Abstract
A method for the decentralised solution of the security constrained optimal power flow (SCOPF) problem in large interconnected power systems is presented. The method decomposes the overall SCOPF problem of a multi-area system into independent SCOPF subproblems, one for each area. The solutions of the SCOPF subproblems of the different areas are co-ordinated through a pricing mechanism until they converge to a reduced scope central SCOPF solution. The prices used for the co-ordination of the subproblem solutions are the prices of electricity exchanges between adjacent areas. The reduced scope SCOPF of a multi-area power system is a SCOPF with a reduced set of security constraints, in which the effects of contingencies outside an area on monitored elements within the area are ignored. Test results from the application of the method to the IEEE three-area RTS-96 and to the Balkan power system are presented. [ABSTRACT FROM AUTHOR]
Electricity, High voltages, Electric lines, Filters & filtration, and Computer simulation
Abstract
The underlying theory and model of capacitive voltage substations and its associated problems are described. This system is intended to supply electricity to rural communities directly from high-voltage transmission lines. This technique leads to important cost reductions when compared with conventional alternatives. However, in several transient cases, some problems such as ferroresonance and overvoltages could occur in these substations. Using a developed capacitive substation model these transient cases are simulated. A suitable filter is designed to damp overvoltages due to ferroresonance. Analytical aspects of filter design are presented and some computer simulation tests are provided to highlight the usefulness of the proposed filter. [ABSTRACT FROM AUTHOR]