Evaluation Of Available Transfer Capability Research Articles

Dynamic available transfer capability computation using a hybrid approach

In a restructured electricity market, accurate evaluation of available transfer capability (ATC) with dynamic constraints is a challenging task. An approach to determine dynamic ATC, utilising the benefits of a direct method as well as time-domain simulation method, has been developed. Structure-preserving energy function model, which retains the topology of the network, along with transient stability limit, has been used to compute dynamic ATC for bilateral as well as multilateral transactions in an electricity market. Constant impedance as well as composite models for real power loads have been considered. A new contingency severity index, which takes into account the impact of transactions on the severity of the contingencies, has been proposed to reduce the list of credible contingencies to be considered in determining the ATC. To demonstrate the effectiveness of the proposed method, it has been tested on 10-machine, 39-bus New England system and a practical 60-machine, 246-bus Indian system.

Evaluation of available transfer capability using fuzzy multi-objective contingency-constrained optimal power flow

In trying to determine the available transfer capability (ATC), this paper primarily sets out to develop a fuzzy logic approach to parallelizing contingency-constrained optimal power flow (CCOPF). This algorithm may be used by utilities to optimize economy interchange for severe contingencies analyzed without disclosing details of their operating costs to competitors. In fact, the ultimate objective of fuzzy multi-objective CCOPF (FMCCOPF) is to carry out the minimization of both the base case (pre-contingency) operating cost and the post-contingency correction times as conflicting but fuzzy goals. Besides, the Benders decomposition is applied to partition the fuzzy formulation with contingency constraints, which allows for post-contingency corrective rescheduling, motivated by the improvement of computational efficiency using parallel processing. The feasibility of the proposed method is comprehensively realized by a comparison with the conventional optimal power flow (OPF) and the CCOPF with respect to the same array of transactions, base case, and generator/line outages for the IEEE-30 bus system and the IEEE-118 bus system.

The Evaluation of Stochastic Available Transfer Capability

Due to uncertainty in bus loading, the evaluation of the available transfer capability (ATC) between two points in a network also becomes uncertain. The ATC is a measure of ‘available capacity’ in a power transmission system beyond already committed uses, i.e., beyond base case loading. A stochastic power flow algorithm can be used to help quantify and evaluate the uncertainty of the ATC. The limitations considered in the stochastic ATC algorithm are: circuit stability limits, transmission line thermal rating limits, and bus voltage magnitude limits. Transmission circuit outages, while important and also of a stochastic nature, are not considered. The analytical calculation of stochastic ATC is described and tested using the WECC 179 bus system. The analytical calculation is compared to a computationally intensive Monte Carlo calculation. The value of stochastic modeling of ATC relates to a realistic evaluation of power exchange.

Dynamic voltage stability constrained ATC calculation by a QSS approach

The evaluation of Available Transfer Capability (ATC) in deregulated power system should take into account thermal limits, transient, steady-state and dynamic angle stability as well as the voltage stability limit. The consideration of voltage stability in the determination of ATC, however, was not well researched before. On the other hand, under the power market environment, voltage instability becomes a more important consideration in many countries in recent years, especially when following a large disturbance in a heavily stressed power system over long distances. A new ATC determination scheme using Quasi-steady-state (QSS) approximation is proposed in this paper and implemented on a test system. The performance of the QSS approximation is also compared with the Full-Time-Scale (FTS) simulation. From the results, it is shown that the proposed scheme can evaluate ATC with dynamic voltage stability constraints accurately and the calculation speed is accelerated considerably to meet the real-time requirement.

Fast evaluation of available transfer capability using cubic-spline interpolation technique

This paper presents a new computationally fast and accurate method for evaluating available transfer capability (ATC) based on a curve fitting technique so-called as the cubic-spline interpolation technique. The advantage of the technique used in the computation of ATC is that it has the ability to reduce the time consuming ac power flow computations. The cubic-spline interpolation technique traces the curves of voltage magnitude and power flow variations with respect to the increase of real power transfer. ATC is then determined at the point where the voltage or power flow limits intersect the curves. Prior to the ATC evaluation, contingency ranking and selection techniques are used to define the critical lines in a system that can adversely affect the transfer capability assessment. The effectiveness of the proposed method is verified by illustrating the ATC evaluation on a practical test system. ATC results obtained from the proposed cubic-spline interpolation technique prove that the method is satisfactorily accurate and it is faster than the ATC method using the recursive ac power flow computations.

Calculation of risk and statistical indices associated with available transfer capability

A complete evaluation of available transfer capability (ATC) involves the determination of total transfer capability (TTC), transmission reliability margin (TRM) and capacity benefit margin (CBM). Due to the stochastic nature of power system behaviour, which is considered by TRM, it is important to assess ATC from a statistical and risk analysis point of view. Based on a combination of repeated AC power flow and Monte Carlo methods, risk assessment of the ATC value is described and a set of statistical indices and plots is presented, which provides important information for transmission customers, system operators and power marketers. In addition, two methods of incorporating CBM into ATC are presented and compared. Case studies with the IEEE Reliability Test System (RTS) demonstrate the effectiveness of the proposed methods, indices and plots. The impact of uncertainty, CBM and methods of incorporating CBM on ATC are also investigated.

Available transfer capability (ATC) evaluation by stochastic programming

Based on stochastic programming, from the viewpoint of operational planning, a novel methodology is proposed to evaluate the available transfer capability (ATC) of prescribed interfaces in interconnected power networks. Recognizing the uncertainties of power systems, an effective stochastic model of ATC evaluation is formulated, in which the availability of generators and circuits as well as load forecast error are considered as random variables. A hybrid method that takes advantage of both two-stage stochastic programming with recourse (SPR) and chance constrained programming (CCP) is proposed to deal with this complex problem, which includes both discrete and continuous variables. Case studies with a reduced practical system are presented. The performance clearly illustrates the effectiveness of the proposed methodology.