Reactive power and voltage control in deregulated environment

Reactive power support and Voltage control is a key type of ancillary services In the deregulated electrical power market. A review of some important issues of reactive power support, Including cost analysis, reactive power pricing, valuation, is presented in this paper. An Optimal Power Flow (OFF) is used based on real time pricing theory. Two object functions are modeled respectively: minimization of network loss and minimization of total cost to supply reactive power. A real-valued Genetic Algorithm (GA) Is also used to help searching the global optimum and verify the solutions. An IEEE 30-bus system is used for the studies. © 2005 IEEE.published_or_final_versio

Comparison of Transmission Loss Allocation Methods and Prediction of Losses in Deregulated Power Systems

Transmission losses are a significant component of the amount of power to be generated in order to meet the power demand. Today, in competitive electric energy markets operating under pool-based, bilateral contracts or hybrid model, transmission losses must be allocated among the market participants

Transmission congestion management by optimal placement of FACTS devices

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 13/09/2010.This thesis describes the implementation of the Flexible AC Transmission Systems (FACTS) devices to develop a market-based approach to the problem of transmission congestion management in a Balancing Market. The causes, remedies and pricing methods of transmission congestion are briefly reviewed. Balancing Market exists in markets in which most of the trading is done via decentralized bilateral contracts. In these markets only final adjustments necessary to ensure secure system operation is carried out at a centralized Balancing Market. Each market player can participate in the Balancing Market by submitting offers and bids to increase and decrease its initially submitted active generation output. In this research a method is proposed to reduce costs associated with congestion re-dispatch in a Balancing Market by optimal placement of FACTS devices, and in particular Thyristor Controlled Phase Shifter Transformers (TCPST). The proposed technique is applicable to both Mixed Integer Linear Programming (MILP) and Mixed Integer Non-Linear Programming (MINLP). In the MILP a power system network is represented by a simplified DC power flow under a MILP structure and the Market participants' offers and bids are also represented by linear models. Results show that applications of FACTS devices can significantly reduce costs of congestion re-dispatch. The application of the method based on the MINLP creates a nonlinear and non-convex AC OPF problem that might be trapped in local sub-optima solutions. The reliability of the solution that determines the optimal placement of FACTS devices is an important issue and is carried out by investigation of alternative solvers. The behavior of the MINLP solvers is presented and finally the best solvers for this particular optimization problem are introduced. The application of DC OPF is very common in industry. The accuracy of the DC OPF results is investigated and a comparison between the DC and AC OPF is presented

A study of bilateral contracts in a deregulated power system network

One of the main objectives of deregulating the electric power industry is to introduce competition in the electricity business and prevent monopolies. The introduction of deregulation has, however, led to confusions in the areas of transmission network loss sharing and the responsibility of generation of reactive power. Because, under deregulation, the business and economic decisions in a power system are made by each individual vendor/utility in a decentralized manner. Each power producing entity operates on the principle of profit maximization by optimizing its production cost of real power, reactive power and the spinning reserve margin. Two methods have been developed to determine a generator's share of transmission loss in a deregulated power system. They are: the Incremental Load Flow Approach (ILFA) and the Marginal Transmission Loss Approach (MTLA). The ILFA employs an iterative load flow technique. The MTLA finds the transmission loss share of a generator by utilizing the marginal rate of transmission loss. Both methods are very straightforward and can be implemented by an electric utility or an Independent System Operator (ISO) with little difficulty. Results obtained from both approaches agree well. The details of the two methods along with some numerical examples have been presented in this thesis. The profit maximization objectives of any generating entity or an IPP not only depends on transmission loss allocation but also on the production levels of real power, reactive power and spinning reserve. A model for profit maximization by a generating entity or an IPP who is interested to sell both real and reactive power is developed and presented in this thesis. In many jurisdictions, a power producer has the option for selling spinning reserve in addition to real and reactive power. A profit maximization model based on the forecasted market price of real power, reactive power and spinning reserve has been developed and presented in this thesis. The model would help a producer to decide the production levels of these three commodities in order to realize the maximum profit. Zero profit conditions have been considered along with the profit maximization model to determine the minimum acceptable price vectors of these three commodities. A small test network and the IEEE 24-Bus Reliability Test System (RTS) have been utilized to conduct studies and illustrate the concepts with numerical examples

Nordic Electricity Congestion's Arrangement as a Model for Europe: Physical Constraints or Operators' Opportunity

Nordic Electricity Congestion's Arrangement as a Model for Europe: Physical Constraints or Operators' Opportunit

Impact of optimally placed VAR support on electricity spot pricing

In view of deregulation and privatization processes, electricity pricing becomes one of the most important issues. The increases in power flows and environmental constraints are forcing electricity utilities to install new VAR equipment to enhance network operation. In this thesis a nonlinear multi-objective optimization problem has been formulated to maximize both social welfare and the maximum distance to collapse point in an open power market using reactive support like Static Var Compensator (SVC). The production and consumption costs of reactive power are intended to provide proper market signals to the electricity market agents. They are included in the multi-objective Optimal Power Flow (OPF) coupled with an (N-1) contingency criterion which is based on power flow sensitivity analysis.;Considering the cost associated with the investment of VAR support, placing them at the optimal location in the network is an important issue. An index to find the optimal site for VAR support considering various technical and economical parameters based on Cost Benefit Analysis (CBA) is proposed. The weights for these parameters are computed through an Analytic Hierarchy Process (AHP). A new approach of transmission pricing calculation taking VSC-OPF based multi-objective maximization as the objective and studied the impact of SVC on it. The integrated approach is illustrated on a 6-bus and a standard IEEE 14-bus test systems and shows promising results

Market-based transmission congestion management using extended optimal power flow techniques

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 5/9/2001This thesis describes research into the problem of transmission congestion management. The causes, remedies, pricing methods, and other issues of transmission congestion are briefly reviewed. This research is to develop market-based approaches to cope with transmission congestion in real-time, short-run and long-run efficiently, economically and fairly. Extended OPF techniques have been playing key roles in many aspects of electricity markets. The Primal-Dual Interior Point Linear Programming and Quadratic Programming are applied to solve various optimization problems of congestion management proposed in the thesis. A coordinated real-time optimal dispatch method for unbundled electricity markets is proposed for system balancing and congestion management. With this method, almost all the possible resources in different electricity markets, including operating reserves and bilateral transactions, can be used to eliminate the real-time congestion according to their bids into the balancing market. Spot pricing theory is applied to real-time congestion pricing. Under the same framework, a Lagrangian Relaxation based region decomposition OPF algorithm is presented to deal with the problems of real-time active power congestion management across multiple regions. The inter/intra-regional congestion can be relieved without exchanging any information between regional ISOs but the Lagrangian Multipliers. In day-ahead spot market, a new optimal dispatch method is proposed for congestion and price risk management, particularly for bilateral transaction curtailment. Individual revenue adequacy constraints, which include payments from financial instruments, are involved in the original dispatch problem. An iterative procedure is applied to solve this special optimization problem with both primal and dual variables involved in its constraints. An optimal Financial Transmission Rights (FTR) auction model is presented as an approach to the long-term congestion management. Two types of series F ACTS devices are incorporated into this auction problem using the Power Injection Model to maximize the auction revenue. Some new treatment has been done on TCSC's operating limits to keep the auction problem linear

Allocation of transmission losses to determine tariff

The recent widespread restructuring and unbundling of the electricity industry has introduced some changes in the organization of the sector, thereby creating a more competitive environment in which each participant must bear its own cost and be responsible for its own contribution to losses in the system. The allocation of transmission losses has become an important issue as this determines how and what to charge each of the participants in the industry. This allocation is best assessed and based on their individual contributions to grid losses. Earlier methods used in loss allocation include: The Pro rata approach which arbitrarily allocates 50% each to the load and generator; the Marginal procedure allocation, which is either positive or negative; the Proportional sharing method which bases its allocation on the Kirchhoff’s current law and allocates no losses to the transmission line and the Equilateral bilateral exchange (EBE) method. Most of the other methods, such as the Game theory method, Circuit theory method, Graph theory method, and Optimization methods are either mathematically complex in operation or time-consuming. And till date, none of these methods could be used to allocate transmission losses with fairness and transparency. Currently, power loss measurements have been estimated based on ideal conditions in which there exist a balanced load and reactive power, while the inefficiency caused by distortion and the unbalanced load is not usually taken into consideration. This research introduces a novel and a fairer method of determining power losses by using the Thévenin impedance in calculating the line parameters used in the determination of power losses. Since losses associated with a transmission power line depend on the wire resistance and the line current (I2 R), the Thévenin equivalent of the system is calculated from the point of connecting each participant (generator or load), i.e. the point of common coupling, to determine the system losses without prior knowledge of the power system supply quantities. This thesis identifies the avoidable losses in the system, which participants pay for because of the inadequacy of current methods which use only reactive powers (inductive and capacitive) to determine the power losses in the allocation of losses and in the calculation of the power system tariff. This report elucidates how to estimate the losses that can be avoided by the participants. This loss is equal to the numerical power difference in the conventional power loss and the new power loss calculation method which utilizes the general power theory where two components that are orthogonal to each other, making non-active power (reactive power and distortion power) are used. This difference, which is an extra loss created by the participants, can be conserved to reduce power generation cost and tariffs. This method which was tested on a standard IEEE test system is transparent, fair and requires a comparatively short time to execute, making it suitable for decision making thus emphasizing the importance of the proposed solution

Power market analysis tool for congestion management

The privatization and deregulation of electricity markets has increased competition and electricity may be produced and consumed in amounts that would cause the transmission system to operate beyond transfer limits---the system is congested. Hence, congestion management is a fundamental transmission management problem. In this thesis, a power market analysis tool is designed for congestion management. The tool creates an interface between PowerWorld (c), a professional software tool to compute power flows, and MATLAB RTM. The tool helps in analyzing power flow results, batch-processing of large case studies, and providing the user with options to manage congestions. A graphical user interface has been designed to help the user learn and interact with the tool.;Based on the generator and load bid data, the tool performs (N-1) security analysis. In case of congestion, the user can choose one of three congestion relief methods. Transmission Line Relief Sensitivity (sensitivities of line flows to load curtailment), Economic Load Management (a product of three indices that measure (i) the sensitivity of the line flow to load curtailment, (ii) the level of customer incentive to cut down consumption, and (iii) the customer\u27s acceptable range of curtailment), and VAR Support (installment of additional VAR devices). The congestion alleviation methods are explained and tested on a six bus test system and the IEEE 24 bus Reliability Test System