D.T. McGillis

Intelligent-Based Approach to Islanding Detection in Distributed Generation

This paper introduces a new intelligent-based approach for detecting islanding in distributed generation (DG). This approach utilizes and combines various system parameter indices in order to secure the detection of islanding for any possible network topology, penetration level and operating condition of the DG under study. Hence, every parameter index displays characteristics for a given set of events. The proposed technique uses the data-mining technology to extract information from the large data sets of these indices after they are screened off-line via massive event analyses using network simulations. The technique is tested on a typical DG with multiple distributed resources and the results indicate that this technique can successfully detect islanding operations. In addition, this technique can also overcome the problem of setting the detection thresholds inherent in the existing techniques by optimizing their settings

Studies of bilateral contracts with respect to steady-state security in a deregulated environment

Under a deregulated environment, electricity consumers and suppliers will be permitted to establish various bilateral service contracts. The transmission company however will only have to honour and execute these bilateral contracts as far as the system design and operating conditions permit. A fundamental question is to what extent the system security could affect these contracts and what kinds of system reinforcements will be required to meet the future contract needs. This paper describes a series of studies modelling the bilateral contracts by using a transaction matrix (T). The concept of the transaction matrix is to expand the conventional load flow variables such as generations (Pg) and loads (Pd) into a 2-dimensional matrix (T). Each element of T, namely t/sub ij/, corresponds to a bilateral contract between a supplier (Pg/sub i/) and consumer (Pd/sub j/). A generalized linear programming formulation is then proposed to solve various system operation and planning problems under a deregulated environment subjected to the steady-state security constraints (e.g. generation and line flow limits). Examples are presented to illustrate how to use this formulation to maximize any bilateral contract, individual generation or groups of generations; or to minimize the necessary correction needed for a proposed transaction matrix (T/sup 0/) in order to comply with the security requirements. Other studies such as the use of Monte Carlo methods to study the behaviour of random bilateral contracts are also presented and discussed.

Mid-point siting of FACTS devices in transmission lines

Many controllers of flexible AC transmission systems (FACTS), such as the STATCOM, the unified power flow controller (UPFC), the PWM asynchronous DC link, the thyristor-controlled series capacitor (TCSC) and the PWM series static VAr compensator have stabilized AC voltage support. Thus, they can be sited at the mid-point of the transmission line, which has been proven by the late E.W. Kimbark, as the optimum location for shunt capacitor compensation. This paper points out that the ability to double the power transfer of the uncompensated line applies also to the aforementioned FACTS devices. The mid-point siting also facilitates the independent control of reactive power at both ends of the transmission line.

Studies of bilateral contracts with respect to steady-state security in a deregulated environment [of electricity supply]

Under a deregulated environment, electricity consumers and suppliers will be permitted to establish various bilateral service contracts. The transmission company however will only have to honour and execute these bilateral contracts as far as the system design and operating conditions permit. A fundamental question is to what extent the system security could affect these contracts and what kinds of system reinforcements will be required to meet the future contract needs. This paper describes a series of studies modelling the bilateral contracts by using a transaction matrix (T). The concept of the transaction matrix is to expand the conventional load flow variables such as generations (Pg) and loads (Pd) into a 2-dimensional matrix (T). Each element of T, namely t/sub ij/, corresponds to a bilateral contract between a supplier (Pg/sub 1/) and consumer (Pd/sub j/). A generalized linear programming formulation is then proposed to solve various system operation and planning problems under a deregulated environment subjected to the steady-state security constraints (e.g. generation and line flow limits). Examples are presented to illustrate how to use this formulation to maximize any bilateral contract, individual generation or groups of generations; or to minimize the necessary correction needed for a proposed transaction matrix (T/spl deg/) in order to comply with the security requirements. Other studies such as the use of Monte Carlo methods to study the behaviour of random bilateral contracts are also presented and discussed. It was concluded that the proposed methodology will be an effective tool to study the intricate relationships between the bilateral contracts and system security.

Expert systems in transmission planning

The state of the field of expert systems and knowledge engineering in transmission planning is reviewed. A detailed analysis of the goals, definition, requirements and methodology of transmission planning is presented. Potential benefits of knowledge-based applications in transmission planning are reviewed. This is followed by a thorough review of the area broken down into subareas or important related topics. The conclusions offer a number of suggestions for possible future research and development. Finally, a detailed bibliography divided into subareas is presented. >

Voltage support by distributed static VAr systems (SVS)

This paper shows that when load centers require Static VAR Systems (SVS) for regulated voltage control, the strategy of using many, small, distributed SVS located at distribution buses is more advantageous than a few large bulk SVS located at the transmission or sub-transmission bus. The advantages are (i) standby to meet N-1 reliability criterion is reduced; (ii) costly high voltage transformers are no longer needed because the SVS can be connected directly to the low voltage distribution buses; (iii) distribution-side voltage support is more effective so that the total MVAr requirement of the distributed SVS is less. Simulation studies have demonstrated that the distributed SVS units operate harmoniously together.

Probabilistic security analysis of bilateral transactions in a deregulated environment

This paper addresses one of the most critical questions in power system operation and planning in a deregulated environment, namely, how to evaluate an electricity transaction on the basis of system security, especially when numerous transactions have to be processed simultaneously. From a planning perspective, the question of how to identify the most suitable reinforcements needed to maintain system security so that all entities (e.g. producers, consumers and traders etc.) can have equal opportunity to buy or sell is also addressed. Monte Carlo simulations are used to construct a large population of random bilateral transaction matrices (BTM) simulating the market activities. Quantitative measures, termed the probabilities of secure transactions (POST), are derived from the simulation results to analyze the feasibility of transactions in terms of security. The impact of firm contracts on system security as measured by POST is also studied under different operating and planning scenarios.

The application of multi-criteria analysis to substation design

This paper presents an approach to substation design based on a multicriteria analysis. It describes the four criteria and how they are applied, first of all to the selection of credible designs and then to the evaluation of these designs to arrive at the most promising result. The substation structure is described in terms of its five composite groups and defined by the single-line diagram and the associated equipment. The process of selecting suitable configurations (single-line diagram) and associated electrical equipment is based on the multi-criteria approach. This approach is further refined to incorporate user preferences with respect to the chosen four criteria so as that the final design is representative of both the design specifications and the concerns of the user.

Fourier methods for estimating power system stability limits

This paper shows how the use of new-generation tools such as a generalized shell for dynamic security analysis can help improve the understanding of fundamental power systems behaviour. Using the ELISA prototype shell as a laboratory tool, it is shown that the signal energy of the network impulse response acts as a barometer to define the relative severity of a contingency with respect to some parameter, for instance power generation or power transfer. In addition, for a given contingency, as the parameter is varied and a network approaches instability, signal energy increases smoothly and predictably towards an asymptote which defines the networks stability limit: this, in turn, permits a comparison of the severity of different contingencies. Using a Fourier transform approach, it is shown that this behaviour can be explained in terms of the effect of increasing power on the damping component of a power systems dominant poles. A simple function is derived which estimates network stability limits with surprising accuracy from two or three simulations, provided that at least one of these is within 5% of the limit. These results hold notwithstanding the presence of many active, nonlinear voltage-support elements (i.e. generators, synchronous condensers, SVCs, static excitation systems, etc.) in the network. >

Reliability comparison of substation designs

This paper introduces the concept of reliability evaluation of substation designs in terms of the cost of lost load. To overcome the problem of dimensionality, the failure states are merged and a linear-programming approach is used to determine the LOLE by means of state-enumeration techniques. Where the single-line diagram of the substation is not symmetrical, an equivalent is constructed, thus giving rise to higher and lower values of LOLE, in other words defining an unreliability region. The average value of LOLE, called the mean evaluation of lost load (MELL), can then serve as an input to the economic comparison of alternative substation configurations.