PERFORMANCE ENHANCEMENT OF POWER SYSTEM BY STATCOM -INTEGRATED ARCHITECTURE

The paper aims to discuss the Performance Evaluation of STATCOM integrated with 118 – IEEE Test System and the Integrated Design Architecture for Efficient Management of Power System. Modern day Power System is constituted of Electrical components integrated with electronic devices and automated with Software. The components hardware and functionality is complex. To support the enhancement of the Life Cycle activities both the physical and the abstract components are modularized. The paper discusses the Key concepts of modularization, and the Life Cycle Stages. Taxonomy of Power Systems is presented. The paper presents the implementation of a modular FACTS device - STATCOM in 118Bus IEEE Test System and the results analyzed

Analysis of Electric Field Intensity in Gas Insulated Busduct

Gas insulated substations (GIS) have received great interest in the recent years. One of the advantages of GIS over conventional substations is their compactness which makes them a favourite for service in urban residential areas. These consists conductors supported on insulator inside on enclosure filled with sulphur hexafluoride (SF6) gas. The voltage withstands capability of SF6 bus duct is strongly dependent on field perturbations such as those caused by conductor surface imperfections and by conducting particle contaminants. These acquire charge due to the electric field intensity. Nearly 50 % of GIS failures are due to metallic conducting particles lifted by electric field and migrate to conductor or insulator initiating breakdown at voltages significantly below the insulation characteristics. This paper analyses the electric field intensity for different dimensional conductor and enclosures at various applied voltages in a three phase Gas Insulated Bus duct. Electric field intensity decreases with increase in diameter of enclosure

Impact of FACTS Devices on Zonal Congestion Management in Deregulated Power System

Congestion management is one of the most important issues for secure and reliable system operations in deregulated electricity market. In most cases, Independent System Operator tries to remove congestion by rescheduling output power of the generators. In this paper, transmission congestion distribution factors based on sensitivity of line real power have been proposed to identify the congestion clusters. The system operator can identify the generators from the most sensitive congestion clusters to reschedule their generation optimally to manage transmission congestion based on generator sensitivity efficiently. The role of thyristor controlled phase angle regulator and Thyristor controlled series Capacitor have been investigated for reducing the transmission congestion cost after locating it optimally in the system based on improved performance index. The effectiveness of the proposed method has been carried out on an IEEE 118 bus system and 62 bus Indian Utility System. Keywords: Congestion zones, Congestion Management, Transmission congestion distribution factors, Thyristor controlled phase angle regulator, Thyristor controlled series Capacitor, Rescheduling, Performance Index, and Sensitivity Index

ATC Enhancement With FACTS Devices Considering Reactive Power Flows Using PTDF

In the present day world power system deregulation is at its full stretch. In this deregulated environment there is a clear need for adequate computation of ATC which is currently being given at most importance. The insertion of FACTS devices in electrical systems seems to be a promising strategy to enhance ATC. In this paper, the viability and technical merits of boosting ATC using TCSC are analyzed. The methods used for determining ATC are linear methods, which are based on MVA loading of the system considering system thermal limit constraints, neglecting bus voltages and static collapse. Power Transfer Distribution Factors, commonly referred to as PTDFs, express the percentage of a power transfer that flows on a transmission facility. They are used to determine the maximum ATC that may be available across the system without violating line thermal limits. The effect of reactive power flows in line loading is not considered in linear ATC which is a major limitation. This paper describes a fast algorithm to incorporate this effect. In this paper the line post transfer complex flow is estimated based on exact circle equation and then ATC is evaluated using active power distribution factors. The effectiveness of the proposed method is successfully demonstrated on IEEE 30-Bus system.DOI:http://dx.doi.org/10.11591/ijece.v3i6.392

Over-the-Scope Clip to the Rescue! A Novel Tool for Refractory Acute Nonvariceal Upper Gastrointestinal Hemorrhage

© 2020 © 2020 The Author(s). Published by S. Karger AG, Basel. Nonvariceal upper gastrointestinal hemorrhage (NVUGIH) is more prevalent than lower gastrointestinal hemorrhage and carries a high risk of mortality in the elderly, especially those with significant cardiovascular comorbidities. Traditional endoscopic methods, such as through-the-scope clips, electrocautery, and epinephrine injection, are frequently used to control these bleeds; however, they carry a 10% risk of rebleeding, and this itself carries a mortality risk of 36%. The larger over-the-scope clips (OTSC) that were initially used for the closure of fistulas and perforations are now gradually being implemented to manage NVUGIH. To our knowledge, we present the first cases to be reported in the literature where OTSC was successfully used as salvage therapy for refractory acute upper gastrointestinal bleeders who failed traditional endoscopic management and interventional radiology-guided embolization of the bleeding artery. We also provide an up-to-date literature review on the use of OTSC and its superiority to traditional endoscopic interventions in the management of complicated NVUGIH

Space Vector Based Hybrid Random PWM Algorithm for DTC-IM Drive To Achieve Superior Waveform Quality

This paper presents a simplified space vector based hybrid random pulsewidth modulation algorithm for direct torque controlled induction motor drive to achieve superior waveform quality and reduced acoustical noise and harmonic distortion. To reduce the complexity involved in the conventional space vector approach, the proposed pulsewidth modulation (PWM) algorithm uses instantaneous sampled reference phase voltages to calculate the actual switching times of the devices. The proposed PWM algorithm modifies the time duration of application of vector V0 (000) by using a factor. By changing the value of this factor many switching sequences can be derived. The proposed PWM algorithm uses 0127, 012 and 721 switching sequences when value takes 0.5, 1 and 0 respectively. In order to achieve superior waveform quality, the harmonic analysis of these sequences is carried out using the notion of stator flux ripple and expressions are derived for mean square flux ripple in terms of imaginary switching times and modulation index. By comparing the instantaneous ripple values in each sampling time interval, the suitable sequence is selected that results in minimum current ripple. Thus, the proposed algorithm gives reduced harmonic distortion when compared with the SVPWM algorithm. As the zero state time is varied randomly according to the operating sequence, randomization effect will occur, which results in reduced dominating harmonics and hence acoustical noise when compared with the SVPWM algorithm. The simulation results validate the proposed algorithm

Space Vector Based Dual Zero-Vector Random Centered Distribution Pwm Algorithm for Direct Torque Control of Induction Motor Drive For Reduced Acoustical Noise

The direct torque control (DTC) technique has been recognized as the viable solution to achieve precise and quick torque response but it suffers from few drawbacks such as high ripple in torque, flux and stator current resulting in increased vibrations and acoustic noise. The conventional SVPWM algorithm gives good performance for control of induction motor drive, but it also produces considerable acoustical noise resulting in increased total harmonics distortion. The deterministic pulse width-modulation (PWM) method adopted in induction-motor drives causes Acoustical noise due to the switching frequency. This paper presents a novel dual zero-vector random centered distribution PWM algorithm for direct torque controlled induction motor drive. The proposed PWM algorithm uses two zero voltage vectors. When the operating modulation index is less than the critical modulation index, the proposed PWM algorithm uses V0 (000) as zero voltage vector. Otherwise, when the operating modulation index is greater than the critical modulation index, the proposed PWM algorithm uses V7 (111) as zero voltage vector. To verify the proposed PWM algorithm, a numerical simulation studies have been carried out and results are presented and compared with classical SVPWM algorithm. The simulation results confirm the effectiveness of the proposed DZRCDPWM algorithm for the considered drive. Key words: DTC, DZRCDPWM, RPWM, SVPWM, Acoustic noise

Performance of SF6 GIB under the influence of power frequency voltages

A method based on particle motion is proposed to determine the particle trajectory in Gas Insulated Substation (GIS) or Gas Insulated Busduct (GIB). In order to determine the movement of a particle in a GIB, an inner electrode diameter of 40mm and outer enclosure diameter of 137mm was considered. Aluminium and copper wires of 0.25mm/10mm and 0.25mm/12mm were considered to be present on the enclosure surface. The motion of the wire (particle) was simulated using the charge acquired by the particles, the macroscopic field that the particle site, the drag coefficient, Reynold's number and coefficient of restitution. In order to determine the random behaviour of moving particles, the calculation of movement in axial and radial directions was done at every time step using rectangular random numbers. Typically for Aluminium wire for a bus duct voltage of 100 kV RMS, the movement of the particle (0.5mm / 8mm) for 2 Sec was computed to be 18.0337mm in radial and 424.4979mm in axial directions and the movement of the particle (0.25mm / 12mm) for 2 Sec was computed to be 22.4249mm in radial and 503.618mm in axial directions. Similar calculation is extended for a typical 200 kV (RMS) Gas Insulated Busduct

Random Zero Vector Distribution PWM Algorithm for Direct Torque Control of Induction Motor Drive for Noise Reduction

The basic direct torque control algorithm gives large ripples in torque, flux and current in steady state, which results in acoustical noise and incorrect speed estimations. The conventional SVPWM algorithm gives good performance for control of induction motor drive, but it produces more acoustical noise resulting in increased total harmonics distortion. The random pulse width modulation (RPWM) techniques have become an established means for mitigation of undesirable side effects in adjustable speed ac drives in particular. Hence, to minimize these anomalies of the drive, this paper presents a random zero vector distribution (RZVDPWM) algorithm for direct torque controlled induction motor drive. The proposed random zero vector distribution PWM (RZVDPWM) algorithm distributes the zero state time between the two zero voltage vectors. To validate the proposed PWM algorithm, simulation studies have been carried out and results are presented and compared. From the results, it can be observed that the proposed RZVDPWM algorithm gives reduced acoustical noise when compared with space vector pulse width modulation (SVPWM) algorithm