Adistribution system suffers from current as well as voltage-related power-quality (PQ) problems, which include poor power factor, distorted source current, and voltage disturbances. A DSTATCOM, connected at the point of common coupling (PCC), has been utilized to mitigate both types of PQ problems. When operating in current control mode (CCM), it injects reactive and harmonic components of load currents to make source currents balanced, sinusoidal, and in phase with the PCC voltages. In voltage-control mode (VCM), the DSTATCOM regulates PCCvoltage at a reference value to protect critical loads from voltagedisturbances, such as sag, swell, and unbalances. However, the advantages of CCM and VCM cannot be achieved simultaneously with one active filter device, since two modes are independent of each other. In CCM operation, the DSTATCOM cannot compensate for voltage disturbances. Hence, CCMoperation of DSTATCOMisnot useful under voltage disturbances, which is a major disadvantage of this mode of operation.
The integration of the DG with the utility distribution network offers a number of technical, environmental and economic benefits. It also gives a great opportunity for distribution utilities to improve the performance of networks by reducing its losses. The technical challenges associated with the DG can be subdivided into three categories: - The system interface to the grid. - Operation and control of the DG. - Planning and design. This work focuses on the first and second categories and aims to investigate a SVPWM algorithm for high power voltage source three level neutral point clamped inverter with operation and control system in sinusoidal mode. This technique provides the nearest switching vectors sequence to the reference vector and calculates the on-state durations of the respective switching state vectors. We used commonly know nearest three vector (NTV) approach. The calculations are only depends on the modulation index and reference vector angle. The work describes systematically the algorithm development, system analysis, DSP based implementation and extensive evaluation study to validate the modulator performance. The interfacing between the grid and DG through SVPWM
This book presents a non-destructive automated damage detection system for the Armored Vehicle Launched Bridge. The goal of the system is to automate the damage detection procedure and enable early detection of structural damage. The book covers both practical design issues and new theoretical developments in the area of non-destructive damage detection using strain energy mode shapes. Provided is a detailed description of the bridge testing in sinusoidal dwell and random burst modes of operation. The book also covers traditional and a novel non-baseline variation of the strain energy method. Also described is a fuzzy expert system that detects and localizes damage on noisy data. Investigated theoretical issues present new developments in the area of damage detection using strain energy mode shapes. An analytical study of the numerical properties of the strain energy processing allows proper selection of the sampling interval during acquisition of the displacement mode shapes, minimizing the effects of measurement noise and providing maximum sensitivity to damage, while improving the accuracy of damage location.
Cables have been frequently used in many sorts of structure such as bridges, guyed towers, cable-supported roofs, between others. From a structural point of view, cables are flexible and lightly damped and their behaviours may exhibit various dynamical problems. Early studies neglected the inherent nonlinearities of the model that are responsible for the cable vibrations, coupling mode of vibration and cable-deck interaction. In this study, the characteristic dynamic behavior in cable-stayed bridges is analyzed by taking into account the inherent nonlinearities which governs the cable response. The mathematical model consists of a hanging cable between two supports at different heights when is parametrically excited by a sinusoidal displacement in one of the anchorages. It is a simplified model of the vibrations induced by the deck to the cables that belong to a cable-stayed bridge. A parametric study of the cable response is carried out making use of the tools of the Geometric Theory for Dynamical Systems. This work belongs to a general and thorough study that has been carried out by the Departments of Civil Engineering and Mathematical Engineering at the University of Bristol.
The motivation for this book was the increase in the appearance of ferroresonance oscillation in substations. The price pressure on the operating authorities and as well on component manufacturers i.e. for instrument transformer, power transformer and grading capacitors for high-performance circuit breakers has led to gradually increasing demands on power system and components.In the IEC Dictionary the following definition can be found for ferroresonance: "a resonance of the capacitance of an apparatus with the inductance of saturable magnetic circuit of an adjacent apparatus".Ferroresonance refers to non-linear oscillations that can occur in power systems where inductive components with a ferromagnetic core, together with capacitances and an AC voltage source comprise a system capable of oscillation.In contrast to a linear resonant circuit, a circuit with non-linear inductance exhibits no well-defined resonance frequency. A sinusoidal source voltage of a fixed frequency can excite different frequencies (harmonic and subharmonic frequencies). In addition, the amplitude of the excited oscillations is not limited only by the power loss in the resonant circuit. For each oscillation mode, a resultant oscillation amplitude can be found.This book provides an overview of the undesired phenomenon of ferroresonance oscillations in high and medium voltage networks in connection with the inductive voltage transformers (VT). Ferroresonance oscillations can cause considerable damage to the VT and neighboured equipment. Because of the various forms of manifestation, cases of ferroresonance are not always recognized as such.The book is addressed to designers and operators of high voltage power installations and manufacturers of inductive voltage transformers.