L.T.G. Lima

Bio: L.T.G. Lima is an academic researcher. The author has contributed to research in topics: Electric power system & Transfer function. The author has an hindex of 5, co-authored 6 publications receiving 555 citations.

Determination of suitable locations for power system stabilizers and static VAr compensators for damping electromechanical oscillations in large scale power systems

Abstract: Efficient algorithms are presented for the solution of two important problems in the area of damping control of electromechanical oscillations in large-scale systems. The proposed algorithms allow the determination of: the most suitable generators for installing power system stabilizers; the most suitable buses in the system for placing static VAr compensators in order to damp the critical modes of oscillation. These algorithms involve the calculation of transfer function residues and represent an important extension of the powerful methodology described by V. Arcidiaconos et al. (see IEEE Trans. Power Apparatus and Systems, vol.PAS-99, p.769-78, 1980), whose use was up to now restricted to power systems of limited size. A major advantage of this methodology is that there is no limitation on the degree of modeling of the power system being studied. >

Computing dominant poles of power system transfer functions

Abstract: This paper describes the first algorithm to efficiently compute the dominant poles of any specified high order transfer function. As the method is closely related to Rayleigh iteration (generalized Rayleigh quotient), it retains the numerical properties of global and ultimately cubic convergence. The results presented are limited to the study of low frequency oscillations in electrical power systems, but the algorithm is completely general.

Efficient methods for finding transfer function zeros of power systems

Abstract: The authors describe algorithms suited to the efficient calculation of both proper and nonproper transfer function zeros of linearized dynamic models for large interconnected power systems. They also described an improvement to the well-known AESOPS algorithm, formulating it as an exact transfer function zero finding problem which was efficiently solved by a Newton-Raphson iterative scheme. Large power system results are presented. >

Fast small-signal stability assessment using parallel processing

Abstract: Small-signal stability assessment of large power systems is presently obtained on sequential computers through the partial eigenanalysis of sparse matrices. This paper describes the implementation of a power system eigenanalysis computer code, of production level, into an advanced parallel processing machine. Eigenvalues are calculated by the lop-sided simultaneous iteration algorithm implemented on a parallel computer, Intel iPSC/860. Results are presented for two practical power system models, showing the large speed-ups obtained through parallel computation. >

Control strategies for multiple static VAr compensators in long distance voltage supported transmission systems

Abstract: The authors address the small-signal stability and control problems associated with a long distance voltage supported AC transmission system. Linear techniques are used for the control design of multiple static volt-ampere reactive (VAr) compensators along the transmission system. Different voltage control strategies are investigated and additional stabilizing signals are designed using frequency response techniques. A new centralized control strategy is proposed and its performance is shown to be superior to the traditional individual bus voltage control. Linear time responses to step disturbances are included to illustrate the performance of the different control strategies investigated. >

Design of Wide-Area Damping Controllers for Interarea Oscillations

Abstract: This paper develops a systematic procedure of designing a centralized damping control system for power grid interarea oscillations putting emphasis on the signal selection and control system structure assignment. Geometric measures of controllability/observability are used to select the most effective stabilizing signals and control locations. Line power flows and currents are found to be the most effective input signals. The synthesis of the controller is defined as a problem of mixed H 2/H infin output-feedback control with regional pole placement and is resolved by the linear matrix inequality (LMI) approach. A tuning process and nonlinear simulations are then used to modify the controller parameters to ensure the performance and robustness of the controller designed with linear techniques. The design process is tested on the New England 39-bus ten-machine system.

Wide-area measurement-based stabilizing control of power system considering signal transmission delay

Abstract: Recent technological advances in the area of wide-area measurement systems (WAMS) has enabled the use of a combination of measured signals from remote locations for centralized control purpose. The transmitted signals can be used for multiple swing mode damping using a single controller. However, there is an unavoidable delay involved before these signals are received at the controller site. To ensure satisfactory performance, this delay needs to be taken into account in the control design stage. This paper focuses on damping control design taking into account a delayed arrival of feedback signals. A predictor-based H/sub /spl infin// control design strategy is discussed for such time-delayed systems. The concept is utilized to design a WAMS-based damping controller for a prototype power system using a static var compensator. The controller performance is evaluated for a range of operating conditions.

Voltage stability analysis using static and dynamic approaches

Abstract: The authors discuss voltage stability analysis of power systems using static and dynamic techniques. Using a small test system, results of time domain simulations are presented to clarify the phenomenon of voltage instability and to better understand modeling requirements. The same system is then analyzed using a static approach in which modal analysis is performed using system conditions, or snapshots, which approximate different stages along the time domain trajectory. The results obtained using the dynamic and static methods are compared and shown to be consistent. >

Simultaneous tuning of power system damping controllers using genetic algorithms

Abstract: This paper presents a method that simultaneously tune multiple power system damping controllers using genetic algorithms (GAs). Damping controller structures are assumed to be fixed consisting basically of lead-lag filters. The tuning method takes robustness into consideration as it guarantees system stabilization over a prespecified set of operating conditions. Modified GA operators are used in the simultaneous optimization of both phase compensations and gain settings for the stabilizers. The method is applied for global PSS tuning to the well-known New England system and to the coordinated tuning of 22 PSSs in a 1762-bus modified equivalent South-Southeastern Brazilian system.