F.L. Pagola

On sensitivities, residues and participations

This paper presents techniques for the evaluation and interpretation of eigenvalue sensitivities, in the context of the analysis and control of oscillatory stability in multimachine power systems. These techniques combine the numeric power of modal analysis of state-space models with the insight that can be obtained from transfer function descriptions. Relationships with tools from Selective Modal Analysis (namely, participations) are stressed. Examples of applications to a detailed multimachine power system model are given.

On sensitivities, residues and participations: applications to oscillatory stability analysis and control

Techniques are presented for the evaluation and interpretation of eigenvalue sensitivities, in the context of the analysis and control of oscillatory stability in multimachine power systems. These techniques combine the numeric power of model analysis of state-space modals with the insight that can be obtained from transfer-function descriptions. Relationships with tools from selective model analysis (namely, participations) are stressed. Examples of applications to a detailed multimachine power system model are given. >

An eigenvalue sensitivity approach to location and controller design of controllable series capacitors for damping power system oscillations

This paper presents tools and methods to study the application of controllable series capacitors for damping power system electromechanical oscillations. Two problems are discussed-location and controller design. The location of a controllable series capacitor consists of determining the series capacitor of the power system where the modulation of its series reactance will be more effective to damp out the modes of interest. It also involves the selection of the input variable to the controller. The basic design of the controller requires the design of the phase compensation network and the calculation of the controller gain. Small signal models of the power system and the corresponding eigenvalue sensitivities are used to address both problems.

Estimating the loading limit margin taking into account voltage collapse areas

This paper addresses the computation of the margin to the maximum loading limit. In the maximum loading point, the minimum singular value of the load flow Jacobian matrix becomes zero. A new generalized singular value analysis is proposed to compute this critical singular value far away of the singular point. In addition, a second order approximation of the load flow equations is formulated and used to determine the margin to the loading limit in physical terms of MW and MVAr. The proposed algorithm is computationally efficient. It is formulated so that it could consider different models for the power system components. It takes into account operating and equipment limits, such as the reactive power generator limits. The algorithm is tested in two systems: a 6-machines test system, which is a CIGRE benchmark for voltage instability studies; and the IEEE-118 buses system.

Control Design for PID Controllers Auto-Tuning Based on Improved Identification

Abstract Every auto-tuning method for PID controllers has two steps: identification of the process and design of the controller. An identification procedure to obtain two points of the frequency response of the system was presented in (Pecharroman and Pagola, 1999). This paper develops a design method based on the ITAE index. This design procedure is then related to the results of the process identification, yielding a complete auto-tuning method that gives very good results in theory and in practice. A complete test batch is used. The main contribution is that the method is valid for integrating as well as non-integrating processes.

Total least squares and discrete-time line models in HV distance protection

This paper discusses the applicability of the parameter estimation procedure known as total least squares, to the distance protection of high voltage transmission lines. The TLS based algorithm presented in the paper uses a two parameter discrete-time model for the line to be protected. The procedure is able to provide precise results (within specifications) in shorter time than other well known procedures, showing an improved dependability/security compromise. Two algorithms designed for different power line conditions, provide the procedure with adaptive behavior. Trip orders are provided in minimum time, according to the noise level in the current and voltage signals.

Decentralized Secondary Voltage Control and Pilot Bus Selection

Abstract The aim of the secondary voltage control is to maintain voltage magnitudes of several load buses, which have been selected as pilot buses, at their optimal values imposed by the tertiary voltage control. In this paper a comprehensive formulation of the secondary voltage control is presented. Centralized control matrices for an optimal proportional integral control are obtained by the minimization of a performance index. Conditions to achieve a stable closed-loop in a decentralized control scheme are stated. A systematic methodology for selecting pilot buses and for dividing the system in decentralized control areas is presented. The differences between centralized and decentralized control schemes are analyzed in a case study based on the New England 39 bus system.

The role of participation factors in reduced order eigenanalysis of large power systems

The authors present a family of variable transformations which are aimed at improving the performance of selective modal analysis (SMA) algorithms. The value of such transformations has been assessed with participation factors and participation ratios. These transformations are applied at two subsystem levels: generator and area level. It is shown that their successive application allows an important order reduction while maintaining convergence of SMA algorithms. Emphasis is on a specific feature of a family of simple and physically meaningful variable transformations: the feasibility of accumulating the participation of the modes of interest on a few state variables.<<ETX>>

Eigenvalue sensitivities for design of power system damping controllers

This paper presents a comprehensive review of methods to compute eigenvalue sensitivities in large linear dynamic systems. Sensitivities with respect to parameters of feedback controllers are of interest since they are suggested as tools for controller design in such demanding environment. These methods have been developed in the context of small-signal stability of electric power systems and the design of damping controllers. The paper also presents new results obtained in the development of expressions of eigenvalue sensitivities with respect to parameters of damping controllers of series FACTS devices.

PID AUTO-TUNING BASED ON A SECOND POINT OF FREQUENCY RESPONSE

Abstract This paper summarizes a new method for the auto-tuning of PID controllers, and extends it to take into account all the information that the process identification can give. The identification is based on two characteristic points of open-loop frequency response: the ultimate and the crossover frequencies. A 4-parameter model can be obtained and used for controller design based on the ITAE index. The main contribution is that this method makes use of all the information provided by the identification step, suppresses the need for a separation between integrating and non-integrating processes, an can address a wider set of plants.