Investigation of TCSC and SSSC Controller Effects on the Power System

Abstract Electrical power systems have been growing due to the increased demand and various loads and it is getting more and more difficult to provide stability and control. It is possible to increase line transmission capacities and to control these systems by providing reactive power compensation. In the recent years, FACTS (Flexible Alternative Current Transmission System) devices have been used as reactive power compensation elements. The study utilized rapid responding TCSC (Thyristor Controlled Series Capacitor) and SSSC (Static Synchronous Series Compensator) FACTS devices that are formed by power electronics elements. The effects of these devices on voltage stability, on the powers carried on the lines and the losses that occur on the lines were investigated with the simulation and its results

Internal and external determinants of export performance: Insights from Algeria

The internationalization of small and medium‐sized enterprises (SMEs) has been the focus of numerous studies. However, while the attention has thus far been on SMEs operating in developed countries, firms evolving in a developing context, including Africa, have been largely neglected. To address this, and drawing on a dual resources‐based and network‐based view, this study simultaneously investigates the importance of internal and external resources for firms’ export performance and regularity in the context of North African SMEs. Using a sample of Algerian exporters, the study reveals the superiority of discrete resources for boosting export performance and export regularity. These findings provide directions to Algerian SME managers and policymakers as to important factors driving the internationalization process in the developing Algerian context

Crowbar hardware design enhancement for fault ride through capability in doubly fed induction generator-based wind turbines

A crowbar circuit used in doubly fed induction generator (DFIG)-based wind turbines protects the system during transient stability. However, in a large power system, crowbar protection may be insufficient due to over-voltage and inrush currents occurring during balanced and unbalanced faults. Hence, in this study, a crowbar circuit was enhanced for fault ride through capability against balanced and unbalanced faults in a DFIG. The stator and rotor dynamic modeling used a crowbar hardware circuit design with rotor active impedance. Electromotive force voltages were used for the stator-rotor dynamics in the DFIG. Furthermore, crowbar resistance units were designed to meet the fault ride through DFIG requirement. The DFIG behaviors with and without the crowbar hardware circuit design were compared. The balanced and unbalanced faults were also compared in terms of behavior. Results showed that the circuit design of the crowbar hardware enabled the system to promptly become stable and eliminated the oscillations. (C) 2020 ISA. Published by Elsevier Ltd. All rights reserved.WOS:0005714625000012-s2.0-85085073130PubMed: 3242361

Enhancement of new rotor resistance unit for doubly fed induction generator-based wind turbines

It is very important to obtain smooth power and limit over-currents in grid-connected doubly fed induction generator (DFIG)-based wind turbines. Therefore, the rotor resistance unit can be used for power and over-currents control in DFIG. However, it may be insufficient to reduce oscillations in large power systems. This study aims to develop a new rotor resistance unit for low voltage ride through (LVRT) capability in DFIG. Moreover, electromotive-force (emf) models have been also developed in the stator and rotor circuit. The stator emf model of the simulation study was developed in the DFIG for accuracy and speed, while the rotor emf model was developed for over-current occurring in transient situations. In using the new rotor resistance unit and the stator-rotor emf, it was observed that the system stabilized in a short time, and the oscillations formed by the balanced and unbalanced faults on the grid side were damped.WOS:0006424539000042-s2.0-8509861737

Hybrid control approach for low-voltage ride-through capability in doubly-fed induction generator-based wind turbines

Grid-connected doubly-fed induction generator (DFIG)-based wind turbines are very sensitive to voltage dip problems that occur in grid side. Therefore, different low-voltage ride-through (LVRT) capability methods are used to decrease the voltage dip problems. In this study, it is aimed to present a hybrid control approach to provide LVRT capability in DFIG. Moreover, it is aimed to develop electromotive-force (emf) models in a stator-rotor circuit. The rotor emf model is used to compensate for the voltage dip and reduce the oscillations while using the stator emf model to ensure the ease of calculation and accuracy of the simulation study. In the results, this paper is reporting that the hybrid control approach proposed in this study has given yield effective and better results in comparison with those of the conventional DFIG model.WOS:0006443282000062-s2.0-8510004235

Novel active-passive compensator-supercapacitor modeling for low-voltage ride-through capability in DFIG-based wind turbines

Low-voltage ride-through is important for the operation stability of the system in balanced- and unbalanced-grid-fault-connected doubly fed induction generator-based wind turbines. In this study, a new LVRT capability approach was developed using positive-negative sequences and natural and forcing components in DFIG. Besides, supercapacitor modeling is enhanced depending on the voltage-capacity relation. Rotor electro-motor force is developed to improve low-voltage ride-through capability against not only symmetrical but also asymmetrical faults of DFIG. The performances of the DFIG with and without the novel active-passive compensator-supercapacitor were compared. Novel active-passive compensator-supercapacitor modeling in DFIG was carried out in MATLAB/SIMULINK environment. A comparison of the system behaviors was made between three-phase faults, two-phase faults and a phase-ground fault with and without a novel active-passive compensator-supercapacitor modeling. Parameters for the DFIG including terminal voltage, angular speed, electrical torque variations and d-q axis rotor-stator current variations, in addition to a 34.5 kV bus voltage, were investigated. It was found that the system became stable in a short time and oscillations were damped using novel active-passive compensator-supercapacitor modeling and rotor EMF.WOS:0004902298000022-s2.0-8507449521

The functional independence measure in spinal cord injured patients: Comparison of questioning with observational rating

Functional independence measure (FIM) is becoming widely used for all aspects of disabling diseases including spinal cord injury (SCI). It is recommended that it is rated by trained clinicians familiar with the patients. We aimed to compare the ratings of those patients who were questioned with those who were observed in a simulated environment