T.T. Lie

Medium term power planning with bilateral contracts

This paper addresses the optimal management of hydropower resources on medium term. The objective is to maximize the expected revenue of a producer, and the decision variables are generation and forward contracts in each period for each scenario. Stochastic linear and nonlinear programming has been used as a framework for modeling and solution. Results are exposited for a Norwegian power producer participating in Nord Pool, the Nordic power exchange.

Price based unit commitment for Gencos in deregulated markets

Some power markets require the Gencos to bid for each individual generator rather than for a group of units. So, it may be desirable to develop unit commitment and generation schedule strategies for individual units. This paper presents a technique to optimize the unit commitment and generation schedules on the basis of the forecasted price. A methodology based on dynamic programming and enumeration has been proposed. The technique has further been extended to optimize the problem for a group of generators. The technique is explained with illustrative examples and then applied to several systems reported in the literature. The results obtained are very encouraging, comparable, if not better, than the results reported earlier in all cases. Finally, the proposed technique is quite simple and requires significantly less computational time.

Estimating economic impact of voltage sags

This paper describes a systematic approach to evaluate the technical as well as the eventual economic impacts from voltage sag disturbances from a customers perspective. It is illustrated how the influence of voltage sag problem can be evaluated from the knowledge of the system voltage sag performance and the equipment sensitivity. It also takes into consideration the role-played by each equipment towards the performance of the customers load system. This in turn allows the monetary costs of interruption to the system operation as induced by voltage sags to be readily determined. This method should be useful for conducting cost/benefit analysis when designing or improving the configuration of the load system. It is particularly useful for evaluating between alternative power quality conditioning solutions.

Profit based unit commitment in competitive markets

The unit commitment of a thermal power producer is addressed which is based on the price behavior in the spot market. The classical unit commitment objective has been redefined to a profit-maximizing objective to match the competitive market. A new method using heuristic technique in coordination with dynamic programming and nonlinear programming has been proposed to solve the unit-scheduling problem. The proposed technique is first compared with the available techniques and is subsequently applied to the profit based unit commitment (PBUC) problem. The results are compared to evaluate the performance of the proposed technique and the implications of PBUC in the competitive market are discussed.

Enhancing power engineering education through the use of design modules

This paper describes the main features of four design modules that form part of the curriculum for the final year power engineering students at the Nanyang Technological University, Singapore. Through the use of these modules, the students gain an insight into the various aspects of power engineering-including power electronics and drives-and this will hopefully help them in a better understanding of the practical aspects of power engineering, and therefore make them better engineers in the power industry. The four modules described are Generating Capacity Expansion Planning, Rectifier and DC Motor Control, Power Systems Operations Planning, and Security Enhancement using Optimal Power Flow.

Design and application of a nonlinear coordinated excitation and TCPS controller in power systems

This paper presents a new approach to thyristor controlled phase shifter (TCPS) control. We propose a nonlinear coordinated generator excitation and TCPS controller to enhance the transient stability of a power system. The proposed controller is able to control the three main parameters affecting AC power transmission: namely the excitation voltage, phase angle and reactance in a coordinated manner. The TCPS is located at the midpoint of the transmission line. A nonlinear feedback control law is proposed to linearize and decouple the power system. The design of the proposed controller is based on the local measurements only. Digital simulation results are shown to demonstrate the effectiveness of the proposed controller for the enhancement of transient stability of the power system under a large sudden fault.

Empirical dynamic oligopoly behavior analysis in electricity markets

In recent electricity markets, the market structure is more similar to oligopoly market than perfectly competitive market. As a result, market participants can increase profits through exercising strategic bidding, or it is more known as exercising market power. Recently, the concept of conjectural variation and its application to strategic bidding and market power has been introduced in oligopoly electricity market. In this paper, the method for empirically estimating the conjectural variations of firms is proposed. Through the estimates of conjectural variation of generation companies (Gencos), the market behaviors of Gencos can be analyzed. Hence, the system regulator of electricity market may recognize and curb the market power by examining the market behaviors of Gencos. On the other hand, market participants can also analyze the behavior of their rivals and make the optimal decision accordingly. An empirically investigation about dynamic market behavior of firms in an actual electricity market is presented. The null hypothesis and likelihood ratio test will be utilized to analyze the dynamic behavior of firms.