A series facts controller as a voltage fluctuation mitigation equipment: an experimental investigation

This research project addresses the mitigation of voltage fluctuations using a series-connected power electronics-based controller, which belongs to the family of Flexible AC Transmission Systems (FACTS) controllers. These are emerging technologies which have been under continuous development for over a decade, and are now available to the electricity supply industry world-wide, helping to ameliorate a wide range of power system phenomena, to increase power transfers and stability margins. Voltage fluctuation is a complex phenomenon affecting adversely transmission and distribution networks. Bulky fluctuating load, wind farms and large induction motor are the major sources of voltage fluctuations. As the phenomenon propagates, it interacts with other voltage fluctuations contributed by different sources, and affecting neighbouring lighting circuits, giving raise to a phenomenon termed light flicker. To ameliorate such a problem, a well-coordinated operation of advanced voltage mitigation equipment, control strategy and specialised measurements instruments are required. Considerable progress has been made in voltage fluctuations mitigation using shunt FACTS controllers. However, very little work has been reported in tackling the very complex issue of mitigation of voltage fluctuation propagating in the network using series FACTS controllers. To advance this area of research, this project addresses the design and construction of a three-phase scaled-down TCSC prototype and a voltage fluctuations experimental environment, suitable for real-time hardware-in-the-loop testing. The research work carries out a fundamental study of TCSC resonances, which are termed resonance modes. It is found that a non-explicit resonance mode at a=90° exists, and it is termed intrinsic resonance mode. For a well-designed TCSC, only the fundamental and the intrinsic resonance mode should be active. To facilitate the design, a procedure has been identified, based in the synchronisation of resonance modes. To achieve mitigation successfully, a new tailor-made TCSC control strategy, named RT-DIMR, and a flexible virtual flickermeter based on the IEC-61000-4-15 standard are thoroughly developed and integrated under the same real-time computing platform. The RT-DIMR demonstrates its capability for controlling the TCSC under different voltage fluctuation conditions. The lEC-Flickermeter provides online flicker severity indices, information which may be used to asses whether or not the electrical network has been effectively improved. The aim of this research work is to experimentally evaluate the TCSC capabilities to mitigate travelling voltage fluctuations. A scaled-down network and voltage fluctuation sources are constructed to mimic a voltage fluctuations propagation environment. A comprehensive number of experiments are carried out to test the mitigation scheme under a wide range of conditions. The robustness and effectiveness of the mitigation schemes have been thoroughly demonstrated. The newly developed TCSC prototype, scaled-down testing environment and RT-DIMR control strategy recommend themselves not only as an imaginative voltage fluctuations mitigation research tool, but also as a general advanced FACTS research tool

FC³ - 1st Fuel Cell Conference Chemnitz 2019 - Saubere Antriebe. Effizient Produziert.: Wissenschaftliche Beiträge und Präsentationen der ersten Brennstoffzellenkonferenz am 26. und 27. November 2019 in Chemnitz

Die erste Chemnitzer Brennstoffzellenkonferenz wurde vom Innovationscluster HZwo und dem Fraunhofer-Institut für Werkzeugmaschinen und Umformtechnik IWU durchgeführt. Ausgewählte Fachbeiträge und Präsentationen werden in Form eines Tagungsbandes veröffentlicht.The first fuel cell conference was initiated by the innovation cluster HZwo and the Fraunhofer Institute for Machine Tools and Forming Technology. Selected lectures and presentations are published in the conference proceedings

Robotics 2010

Without a doubt, robotics has made an incredible progress over the last decades. The vision of developing, designing and creating technical systems that help humans to achieve hard and complex tasks, has intelligently led to an incredible variety of solutions. There are barely technical fields that could exhibit more interdisciplinary interconnections like robotics. This fact is generated by highly complex challenges imposed by robotic systems, especially the requirement on intelligent and autonomous operation. This book tries to give an insight into the evolutionary process that takes place in robotics. It provides articles covering a wide range of this exciting area. The progress of technical challenges and concepts may illuminate the relationship between developments that seem to be completely different at first sight. The robotics remains an exciting scientific and engineering field. The community looks optimistically ahead and also looks forward for the future challenges and new development

Investigation of a three-phase forced-commutation series capacitor operating with variable-voltage and variable-frequency systems

PhD ThesisThis thesis investigates the use of a three-phase forced-commutation series capacitor (FCSC) for power factor correction in stand-alone variable-voltage variable-frequency (VVVF) systems. Two environmentally-friendly applications are chosen to represent the VVVF systems. The first application is a renewable energy resource as a direct drive wave energy conversion (WEC) buoys. The second application is the more electric aircraft (MEA). In such systems, permanent magnet PM generators are most commonly used. A generator-set generally consists of a three-phase generator connected directly to a conventional three-phase diode bridge rectifier for simplicity and cost reduction. Due to the high inherited inductance of the PM generators used in such applications, this configuration suffers from a poor power factor as a result of commutation overlap. Several controlled series compensator (CSC) topologies have been employed for decades in power systems where the voltage levels and frequency are fixed. However, in applications such as WEC and MEA, the voltage and frequency vary. Therefore, in this work, a variable switched capacitor is used in order to inject a capacitive reactance and therefore compensate the inductive reactance of the generator, which prevents power factor degradation. In a VVVF system, it is important to inject variable capacitive reactance since the inductive reactance changes with frequency variations. Five commonly used CSC circuits are compared and the FCSC is considered as the most suitable circuit topology which is able to cope with a range of frequency variations. This research mainly investigates the performance of the three-phase FCSC circuit when controlled by novel control strategy, in terms of power factor, output voltage, and output power under various load conditions, including constant and variable load. The harmonic content of the three-phase FCSC is also investigated in order to propose this topology for MEA power system. In an aerospace system, the power quality is required to meet high standards and harmonic distortion should not exceed the limited level set by aerospace industry authorities. Therefore, several types of conventional power factor corrector (PFC) are excluded from aerospace systems, due to the associated distortion levels. Preface Abstract iv In this thesis, a novel symmetrical duty cycle control (SDCC) scheme is proposed in order to qualify the three-phase FCSC converter to be employed in different ranges of frequency variation, including 1-3 Hz for wave energy and 50-500 Hz as part of aircraft frequencies. The approach is simple to implement, with no need for a sophisticated controller design. The switch duty cycle is a function of the supply frequency and this allows the FCSC circuit to cope with frequency variation. The modes of operation for both single and three-phase circuit topologies are presented. The three-phase FCSC circuit is designed and tested in the laboratory environment. The performance of the three-phase FCSC circuit when using SDCC is tested experimentally and assessed by comparison of its performance with that of the conventional three-phase diode bridge rectifier. Experimental and simulation results validate the capability of the three-phase FCSC- rectifier to improve the power factor to approximately unity in addition to increasing the output voltage and power at higher voltage and frequency values. However, only limited improvements are achieved at the lower values of the frequency spectrum.Ministry of Higher Education and Scientific Research of Ira