Glauco N. Taranto

Simultaneous tuning of power system damping controllers using genetic algorithms

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.

A Real-Time Voltage Instability Identification Algorithm Based on Local Phasor Measurements

This paper proposes a new voltage instability risk indicator based on local phasor measurements at fast sampling rate. The effectiveness of the indicator is analyzed at EHV load and ldquotransitrdquo buses. The risk criterion is based on the real-time computation of the Thevenin equivalent impedance of the classic electrical circuit given by an equivalent generator connected to an equivalent load impedance through an equivalent connecting impedance. The main contribution of the paper is the innovating algorithm utilized on the real-time adaptive identification of the Thevenin voltage and impedance equivalents. The algorithm performance is shown through a detailed sensitivity analysis. The paper presents important numerical results from the actual Italian EHV network.

Benefits of applying secondary voltage control schemes to the Brazilian system

This paper presents preliminary results of the investigations related to the prospective application of a hierarchical coordinated voltage control to parts of the Brazilian EHV network. The paper focuses on the secondary voltage control (SVC) hierarchical level, with emphasis on voltage control by power plants and synchronous condensers. The study system analyzed is the Rio de Janeiro (Rio) Area, which is an energy importing area. Results refer to a heavy load condition, typical of a hot summer day.

A knowledge-based system for supervision and control of regional voltage profile and security

This work presents a knowledge-based system for supervision and control of regional voltage profile and security using fuzzy logic. The control strategies are defined by system operators based on their experience and on off-line studies, which are translated into rules of a hierarchical fuzzy inference system (FIS). Two hierarchical levels, namely, task-oriented control level (high level) and set-point control level (low level) compose the control structure. The high-level control is comprised of a continuous FIS that updates high-side voltage set points at power plants, and a discrete FIS that switches capacitor/reactor banks at the transmission network. The low level control is comprised of automatic voltage regulators and joint var controllers at the power plants. It is presented a simulation study in the Rio de Janeiro (Rio) Area, an energy importing region part of the South/Southeastern Brazilian system.

Automatic Reconnection From Intentional Islanding Based on Remote Sensing of Voltage and Frequency Signals

This paper presents a control strategy for automatic reconnection of a microgrid after an intentional islanding. Remote signals of voltage and frequency at both sides of the coupling circuit breaker are communicated to the generating site, and used as additional signals to the voltage and speed control loops, respectively. The proposed automation strategy is simulated on a real MW-scale microgrid located at a rural area in Rio de Janeiro, Brazil, and supplied by two small hydro synchronous generators. The results show that a smooth reconnection of the microgrid to the utility grid can be achieved when the proposed automation is utilized.

A Hybrid Three-Phase Single-Phase Power Flow Formulation

This paper presents a hybrid power flow formulation unifying three-phase and single-phase (positive sequence) models. Positive sequence modeling is considered at the transmission level network and three-phase modeling is considered at the distribution level. A passive interface between these networks is proposed. The interface is based on a pi element that can represent transmission lines or transformers. The formulation allows both subsystems to be solved simultaneously using the classic Newton-Raphson method. The three-phase subsystem can either be represented in phase or sequence components. Tests in large-scale power systems indicate that the proposed hybrid formulation has the same robust convergence properties of the conventional all-single-phase or all-three-phase Newton-type methods. The use of the proposed formulation is motivated for studies where the focus of the analysis is in the unbalanced three-phase subsystem highly influenced by operating conditions in the single-phase-modeled subsystem.

Using synchrophasors for controlled islanding - A prospective application for the Uruguayan power system

Summary form only given. This paper describes two Wide-Area Protection schemes for controlled islanding of the Uruguayan electrical power system. The first scheme relies only on local signals available for distance protection relays, whereas the second scheme is based both on local and remote synchrophasor measurements. The paper compares results in terms of load shedding amount necessary to maintain system integrity, with and without the proposed protection schemes. The investigation is based on comprehensive transient stability studies using actual dynamical models. Past occurrences that led the system to widespread blackouts have motivated the investigations presented in this paper.

A comparison of classical, robust, and decentralized control designs for multiple power system stabilizers

Summary form only given as follows. Several control design techniques, namely, the classical phase compensation approach, the /spl mu/-synthesis, and a linear matrix inequality technique, are used to coordinate two power system stabilizers to stabilize a 5-machine equivalent of the South/Southeast Brazilian system. The open-loop system has an unstable interarea mode and cannot be stabilized using only one conventional power system stabilizer. Both centralized and decentralized controllers are considered. The different designs are compared and several interesting observations are provided.

Dynamic state estimation in power system using a gain-scheduled nonlinear observer

Time-optimal control of network impedances by a series capacitor has been considered to be a powerful method to enhance transient stability in power systems. A time-optimal control scheme relies on the availability of the synchronous machine angle and speed variables. However, a series capacitor will, in general, not be located near any synchronous machines, such that angle and speed variables cannot be measured locally. In this paper the authors propose a gain-scheduled nonlinear observer to provide estimates of the system states for the control design. Kalman filter design and gain scheduling techniques are used in this procedure. The method is verified by the time simulation of a single-machine infinite-bus power system and is shown to give satisfactory results.

Dynamic Transmission Capability Calculation Using Integrated Analysis Tools and Intelligent Systems

Summary form only given. This paper presents a methodology to calculate the transmission capability between two areas in a power system, considering both static and dynamic security assessment. An optimal power flow (OPF) algorithm is used to compute the transmission capability from the static point of view. The dynamic security assessment of the operating point obtained from the OPF is then evaluated. Transient, voltage and small-signal stability assessment are considered. If any dynamic security criterion is violated, additional constraints are added to the original OPF formulation, and a new and secure transmission limit is calculated. These new constraints can be very simple, such as to limit the transmitted power, or more elaborated, based on some rules obtained from an intelligent system. The results for two test systems have shown the potential benefits of the proposed methodology and the importance of considering different dynamic aspects in transmission capability calculation.