Active filtering of electric power has now become a mature technology for harmonic and reactive power compensation in two-wire (single phase), three-wire (three phase without neutral), and four-wire (three phase with neutral) AC power networks with nonlinear loads. This paper presents a comprehensive review of active filter (AF) configurations, control strategies, selection of components, other related economic and technical considerations, and their selection for specific applications. It is aimed at providing a broad perspective on the status of AF technology to researchers and application engineers dealing with power quality issues. A list of more than 200 research publications on the subject is also appended for a quick reference.

A review of active filters for power quality improvement

Facts Controllers in Power Transmission and Distribution

The application of superconducting magnet energy storage (SMES) to the stabilization of a power system with long-distance bulk power transmission lines which has the problem of poorly damped power oscillations is presented. Control schemes for stabilization using SMES capable of controlling active and reactive power simultaneously in four quadrant ranges are proposed. The effective locations and the necessary capacities of SMES for power-system-stabilizing control are discussed in detail. Results of numerical analysis and experiments in an artificial power-transmission system demonstrate the significant effect of the control by SMES on the improvement of power-system oscillatory performance. >

Application of superconducting magnet energy storage to improve power system dynamic performance

The use of a damping torque technique to examine the efficacy of various control signals, for reactive power modulation of a midpoint-located static VAr system (SVS) in enhancing the power transfer capability of long transmission lines is considered. A new auxiliary signal, the computed internal frequency (CIF), is proposed which synthesizes the internal voltage frequency of the remote generator from electrical measurements at the SVS bus. It is demonstrated that this signal is far superior to other conventional auxiliary control signals in that it allows full utilization of the network transmission capacity. The damping torque results are correlated with those obtained from eigenvalue analysis. >

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Damping torque analysis of static VAR system controllers

The design of a robust controller for a static VAr compensator (SVC) to improve the damping of a power system is presented. The main contributions of the paper are to formulate and to solve the power system damping control problem using robust optimization techniques, and to synthesize the controller with explicit consideration of the system operating condition variations. Nonlinear simulations using the PSCAD/EMTDC software packages have been conducted to evaluate the performance of the closed-loop system. The results have indicated that the designed controller can provide positive damping to the system under a wide range of operating conditions.

Robust SVC controller design for improving power system damping

This paper concerns the application of static reactive compensators (SVCs) to Power transmission systems. Emphasis is placed on stability, and it is shown that SVCs can provide significant benefits in terms of increased transient stabilty liisand improved damping for synchronizing power flow oscillations. The paper includes descriptions Of static VAR compensators, with technical and economic comparisons of different compensators. An SVC system study model is presented which includes provision for modulating reactive compensation in response to a variety of system functions. Study procedures are illustrated which relate sYstem stability objectives to general specifications of SVCs, indluding their locations, regulating slopes, peak reactive power requirements, and modulation control.

Static Reactive Compensation for Power Transmission Systems

The philosophy and design of a subsynchronous oscillation (SSO) relay are discussed. The relay utilizes a unique technique for detecting extremely low magnitudes of subsynchronous current. Special logic is used to determine if the currents represent a potential danger to a turbine-generator. A procedure for selecting relay settings is described.

E. R. Taylor

Papers

Static Reactive Compensation for Power Transmission Systems

A Subsynchronous Oscillation Relay - Type SSO