Transmission Reactive Power Research Articles

An Economic Based Approach for Optimal and Secure Reactive Power Provision in Deregulated Environments

In deregulated electricity markets, reactive power provision is one of the most important ancillary services which is vital for reliable and secure operation of the system. In all electricity markets, economic issues play an important role in market scheduling. This paper presents an algorithm to find optimal reactive power market schedule. The proposed algorithm seeks to minimize a novel three-component payment function which precisely considers economic issues in the market. Two first parts of this function are reactive power provision cost and transmission loss payment. Moreover, another important part of this payment function, which has not considered in the time of reactive power market clearing in literature, is transmission charge payment. As it is shown in simulation results, this term of the function can importantly impact on final reactive power market schedule and consequently on total market payment and final market schedule. Furthermore, due to significant impact of reactive power on system voltage stability, the algorithm tries to schedule reactive power market with an adequate voltage security margin. Sequential quadratic programming is employed to clear the algorithm which is a nonlinear constrained optimization problem. The proposed algorithm is applied on IEEE-24 bus test system with satisfactory results.

Reactive power market management considering voltage control area reserve and system security

This paper presents a new algorithm to optimize reactive power procurement through commercial transactions considering system voltage security. The proposed algorithm minimizes reactive power provision and transmission loss costs in addition to maximizing system voltage security margin through a multiobjective function. In order to maintain the voltage profile of power system during sever contingencies or due to load uncertainty, all voltage control areas (VCA) of the system are detected and then optimal reactive power reserve is provided for each VCA during the market settlement. A four-stage multiobjective mathematical programming method is proposed to settle the reactive power market. The proposed algorithm has been applied on IEEE-RTS test system. The simulation results show the effectiveness of the proposed algorithm for reactive power market management.

Stochastic reactive power market with volatility of wind power considering voltage security

While wind power generation is growing rapidly around the globe; its stochastic nature affects the system operation in many different aspects. In this paper, the impact of wind power volatility on the reactive power market is taken into account. The paper presents a novel stochastic method for optimal reactive power market clearing considering voltage security and volatile nature of the wind. The proposed optimization algorithm uses a multiobjective nonlinear programming technique to minimize market payment and simultaneously maximize voltage security margin. Considering a set of probable wind speeds, in the first stage, the proposed algorithm seeks to minimize expected system payment which is summation of reactive power payment and transmission loss cost. The object of the second stage is maximization of expected voltage security margin to increase the system loadability and security. Finally, in the last stage, a multiobjective function is presented to schedule the stochastic reactive power market using results of two previous stages. The proposed algorithm is applied to IEEE 14-bus test system. As a benchmark, Monte Carlo Simulation method is utilized to simulate the actual market of given period of time to evaluate results of the proposed algorithm, and satisfactory results are achieved.

Sensitivity Measure for Electric Power Load Dispatch Problem

This study performed sensitivity analysis of a multi-objective thermal power dispatch problem and explored a solution methodology exploiting the quality measure approach, which verifies that the non-inferior solutions are uniformly scattered in the objective space. The multi-objective thermal power dispatch problem having non-commensurable objectives, such as operating cost and minimal emissions, is undertaken to meet the systems' real and reactive power demands within generators' capacity constraints. Real and reactive power transmission line flows are obtained from generalized Z-bus distribution factors and are restricted within prescribed limits for the secure operation of a power system. A sensitivity measure is incorporated as a dispersion index to be minimized in order to investigate the effects of random variations in the model parameters of the optimal solution. A non-linear programming problem provides the framework for examining the objectives along with constraints in a weighted sum form of the multi-objective problem. The best objective weights are evaluated by conventional statistical measures, which characterize the correlation coefficients matrix evolution. A quality measure approach is exploited to compare the relative quality of a different set of non-inferior solutions before presenting it to the decision-maker for a final decision. The validity of the proposed method is demonstrated on a 30-bus IEEE power system.

Compound filter-compensating arrengement

A new structure of a compound filter-compensating device is proposed. The developed filter advantages are: automatic variation of higher harmonics compensating parameters with minimal loss of electrical energy at reactive power transmission and electric voltage maintaining at a required level.

Relative electrical distance concept for evaluation of network reactive power and loss contributions in a deregulated system

With the liberalisation of electricity market it has become very important to determine the participants making use of the transmission network. Transmission line usage computation requires information of generator to load contributions and the path used by various generators to meet loads and losses. In this study relative electrical distance (RED) concept is used to compute reactive power contributions from various sources like generators, switchable volt-amperes reactive (VAR) sources and line charging susceptances that are scattered throughout the network, to meet the system demands. The transmission line charge susceptances contribution to the system reactive flows and its aid extended in reducing the reactive generation at the generator buses are discussed in this paper. Reactive power transmission cost evaluation is carried out in this study. The proposed approach is also compared with other approaches viz., proportional sharing and modified Y-bus. Detailed case studies with base case and optimised results are carried out on a sample 8-bus system. IEEE 39-bus system and a practical 72-bus system, an equivalent of Indian Southern grid are also considered for illustration and results are discussed.

Reactive power cost allocation by using a value-based approach

This study proposes a value-based approach to allocate the cost of reactive power production/absorption and the useful VAr reserve provided by the generators. Reactive power support can be segregated into two broad categories: the utilised component of the support and the reactive power reserve component for system security. The utilised reactive power capacity can be decomposed further into the support required for meeting the reactive power loads and that required to meet additional reactive power transmission losses for the MW load shipment. A value-based sensitivity approach has been utilised to compute utilisation factors (UFs) for allocation of the cost of reactive power production/absorption and reserve provision. This method provides transparency in determining the relative utilisation and supply of reactive power by sources to the customers. System operator (SO) can utilise this method for allocation of the cost incurred by the reactive power providers to the load serving entities. Case studies on five-bus test system, IEEE 24-bus reliability test system (RTS) and 75-bus Indian system demonstrate the proposed approach.

Development of a mathematical model for reactive power transmission costs in electric power systems

Development of a mathematical model for reactive power transmission costs in electric power systems

GENETIC-FUZZY-BASED POWER SCHEDULING TECHNIQUE FOR MULTIOBJECTIVE LOAD DISPATCH PROBLEM

The paper proposes the utility of a genetic algorithm (GA) to search for the active and reactive power scheduling for a multiobjective load dispatch problem. Fuzzy decision-making methodology has been applied to decide the fitness function corresponding to each string of active and reactive power generations. All the participating objectives are minimized simultaneously if they attain the maximum satisfaction of their respective membership function and act as fitness function for the generation schedule represented by the string of population. Fuzzy-based number of functional operating constraints, such as equality constraints to ensure real and reactive power balance and inequality constraints for real and reactive power flow through transmission lines, are included as penalties in the fitness function, which guarantee the optimal solution searched by genetic-fuzzy method. The real and reactive power transmission line flows are obtained with the help of generalized Z-bus distribution factors (GZBDF). The validity of the proposed method has been demonstrated on a 25-node sample system comprising five generators.

Reactive power pricing: a conceptual framework for remuneration and charging procedures

A new electrical sector regulation is being implemented in different countries all over the world. The new regulation stresses the role of competitive markets for the procurement and remuneration of ancillary services. Among these services stand the ones associated with reactive power supply and transmission network voltage control in order to maintain the required system security levels. The object of this paper is twofold. On one hand, reactive power supply and voltage control services, which today are bundled, are decomposed in two types: (i) voltage profile management and reactive dispatch, and (ii) voltage regulation. A theoretical approach based on marginal pricing is proposed in order to clarify the principles to remunerate the suppliers and to charge the consumers of these services. On the other hand, a practical organization of reactive supply and voltage service markets is presented to be implemented in a competitive environment.

Wheeling rates of reactive power flow under marginal cost pricing

Wheeling is the transmission of electrical power and reactive power from a seller to a buyer through a transmission network owned by a third party. The wheeling rate is an area of intense research in view of increased deregulation. This paper uses a wheeling rate based on marginal cost pricing and implemented using a modification of the optimal power flow (OPF). A case study based on the IEEE 30-bus system illustrates the magnitudes and ranges that wheeling rates might have in different circumstances. Special attention is paid to reactive wheeling, which cannot be analyzed with a DC model used by previous authors. The ratio of wheeling rates between real and reactive flow shows the importance of the latter. The paper also discusses the significance of this for the trade-off between paying for reactive wheel or investing in compensating plant.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pricing reactive power conveyance

The transmission of electrical power and reactive power from a seller to a buyer through a transmission network obviously has cost implications. The costs incurred are of interest to transmission system owners in view of the increased interest in deregulation in recent years. The paper provides a theory of an ideal conveyance rate based on marginal cost pricing theory. An analysis is made of the marginal cost of reactive transportation using a modification of the optimal power flow algorithm, followed by a case study illustrating the magnitudes and ranges that reactive transportation rates may take on under different circumstances. The ratio of marginal prices between real and reactive power conveyance shows that the costs of reactive power transport is of as much interest because of its impact on real power transport as in itself.

Reactive Power and System Operation—Incipient Risk of Generator Constraints and Voltage Collapse

Starting from the basic physical meaning of reactive power in an alternating current network and its consequences in a simple "source-sink" system (generator and load) the basic criteria are derived explaining why:-transmission of reactive power is difficult and, anyhow, not very efficient;-lack of enough and sufficiently decentralised reactive power sources can cause operating problems in a power system, starting with undervoltage and excessive voltage-drop problems, leading to generator problems and eventually ending up with voltage collapse situations spreading throughout the whole system;-most actual SCADA programs in network control centers don't alert soon enough for this potential risk (not included either in most network - planning - programs).To counter this potentially risky situation some improvements are illustrated to-improve the adequate planning of efficient voltage support sources and of their efficient controls;-improve the awareness of the incipient risks of voltage collapse for the network operators (preventive security control) and even for the network planners through adequate algoritms;-induce adequate preventive measures to avoid those risks through actions on the system and on the generators (capability curves);-provide adequate system automation to block or stop generalized voltage collapse.Disturbance experience and applied subsequent measures will illustrate the theoretical developments