Developing A Medium-Voltage Three-Phase Current Compensator Using Modular Switching Positions

The objective of this thesis is to present the context, application, theory, design, construction, and testing of a proposed solution to unbalanced current loading on three-phase four-wire systems. This solution, known as the Medium-Voltage Unbalanced Current Static Compensator or MV-UCSC, is designed to recirculate currents between the three phases of adistribution system. Through this redistribution of the currents negative- and zero-sequence current components are eliminated and a balanced load is seen upstream from the point of installation. The MV-UCSC as it operates in the distribution system is presented followed by its effect on traditional compensation equipment. The construction of the MV-UCSC as well as 13.8 kV simulations are then shown. Development of the switching positions required by the MVUCSC is then given followed by a variation on this switching position with the intent to reduce part count. Finally, the testing the 13.8 kV three-phase four-wire, neutral-point-clamped, elevenlevel, flying-capacitor-based MV-UCSC connected directly to the grid is presented

Wind Energy Management

The book "Wind Energy Management" is a required part of pursuing research work in the field of Renewable Energy at most universities. It provides in-depth knowledge to the subject for the beginners and stimulates further interest in the topic. The salient features of this book include: - Strong coverage of key topics - User friendly and accessible presentation to make learning interesting as much as possible - Its approach is explanatory and language is lucid and communicable - Recent research papers are incorporate

Resistive-type Superconducting Fault Current Limiter (RSFCL) and Its Application in Power Systems

With the rapid increase in electrical loads, a considerable percentage of global power systems have been stretched to their designed capacity, leading to a sharp rise in the fault current. High fault current levels have severe impact on power systems. They can increase the likelihood of overcurrent damage, which may destroy electrical facilities or even cause system blackout. The resistive-type superconducting fault current limiter (RSFCL) is a device that can help to mitigate the increasing level of fault currents. It can also contribute to the performance, stability and efficiency of electricity grids. In order to promote the RSFCL more effectively, it is essential to study the device itself and conduct simulations regarding the performance and applicability from the system point of view. Chapter 1 and Chapter 2 of this thesis introduced fundamentals of superconductivity and RSFCLs, respectively. In Chapter 3, a power system model was built, and the transient analysis of short-circuit currents was given. Then, the operating principle of RSFCL was explained, and a step-resistance RSFCL model was introduced. To validate the current limiting performance of the SFCL module, wind farm protection schemes were studied under various fault scenarios. After thorough analysis it was concluded that the optimal allocating strategy of SFCLs was the installation of one SFCL at the integrating point of the system model. Chapter 4 presented a comprehensive study on the performance and optimal allocation strategy of RSFCLs. The two power system models used in this chapter were built based on the UK network standard. To assess the impact of incorporating SC material properties on the performance of SFCLs, three different models were compared throughout the study. Although computing time can be reduced when step-resistance and exponential equation models were used, such simplifications led to strong overestimations of the SFCL performance and resulted in wrong conclusion of optimal installing strategies. For both power system models, the simultaneous use of three SFCLs was the best protection strategy in terms of the performance, economic efficiency and reliability of the overall grids. To draw this conclusion, all the potential combinations of two, three, four, and five SFCLs were studied under a wide number of fault scenarios and measuring strategies. In Chapter 5, a series of experiments were performed to study the magnetic field-angular dependence of the critical current of different commercial YBCO samples. We selected ten 2G-HTS tapes with broad differences in width, fabrication process, and laminar structure. The obtained I_c (B,θ) characteristics of HTS samples were applied in the simulation of RSFCLs, showing unneglectable effect on the first peak limiting performance during faults. This study is helpful to the design and simulation of RSFCLs and other HTS applications which require superconducting wires operating inside magnetic fields. In Chapter 6, we presented a High Frequency (HF) AC-assisted quench study of the YBCO conductor. The differences in quench processes triggered by HF AC field were recorded and studied. We found that AC signals of 10 kHz can trigger quench of the HTS tape. Also, the device proved to be effective at guaranteeing uniform quench of the sample. After then, we placed the experimental device in a magnet, to study whether the quench process can be accelerated by external DC magnetic field. It was found that the DC field can reduce the quench time, but its performance was dependent on the amplitude of transport current and the characteristics of HF AC signals. In addition, the angle between the DC magnetic field and the tape surface showed a huge impact on the quench time. Finally, a comprehensive field-angular dependence study about the quench time of the YBCO sample was conducted, revealing the same pattern as J_c (θ,B) dependence of the tape, but with a greater anisotropy. To summarize, this technique showed outstanding performance regarding quench acceleration and tape protection, and therefore has huge potential to be applied in RSFCLs.China Scholarship Counci

Electromagnetic fast-transients in LV networks with ubiquitous small-scale embedded generation

Small-scale embedded generation projects rated below 16A per phase are being integrated into low-voltage distribution networks in ever increasing numbers. Seen from the network operator's perspective as little more than negative load, the commissioning of such generators is subject to compliance with the Fit and Forget connection requirements of ENA Engineering Recommendation G83/1. This thesis has sought to quantify the electromagnetic switching transient implications of integrating very large volumes of embedded generation into the UK's low-voltage supply networks. Laboratory testing of a converter-interfaced PV source has been undertaken to characterise typical switching transient waveshapes, and equivalent representative source models have been constructed in EMTP-ATP. A detailed frequency-dependent travelling wave equivalent of the DNO-approved Generic UK LV Distribution network model has been developed and, by means of extensive statistical simulation studies, used to quantify the cumulative impact of geographically localised generators switching in response to common network conditions. It is found that the magnitude of generator-induced voltage and current transients is dependent on the number of concurrently switched generators, and on their relative locations within the network. A theoretical maximum overvoltage of 1.72pu is predicted at customer nodes remote from the LV transformer terminals, for a scenario in which all households have installed embedded generation. Latent diversity in switch pole closing and inrush inception times is found to reduce predicted peak transient voltages to around 25-40% of their theoretical maxima.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Electromagnetic fast-transients in LV networks with ubiquitous small-scale embedded generation

Small-scale embedded generation projects rated below 16A per phase are being integrated into low-voltage distribution networks in ever increasing numbers. Seen from the network operator's perspective as little more than negative load, the commissioning of such generators is subject to compliance with the Fit and Forget connection requirements of ENA Engineering Recommendation G83/1. This thesis has sought to quantify the electromagnetic switching transient implications of integrating very large volumes of embedded generation into the UK's low-voltage supply networks. Laboratory testing of a converter-interfaced PV source has been undertaken to characterise typical switching transient waveshapes, and equivalent representative source models have been constructed in EMTP-ATP. A detailed frequency-dependent travelling wave equivalent of the DNO-approved Generic UK LV Distribution network model has been developed and, by means of extensive statistical simulation studies, used to quantify the cumulative impact of geographically localised generators switching in response to common network conditions. It is found that the magnitude of generator-induced voltage and current transients is dependent on the number of concurrently switched generators, and on their relative locations within the network. A theoretical maximum overvoltage of 1.72pu is predicted at customer nodes remote from the LV transformer terminals, for a scenario in which all households have installed embedded generation. Latent diversity in switch pole closing and inrush inception times is found to reduce predicted peak transient voltages to around 25-40% of their theoretical maxima

Mineralogical, geochemical and microstructural characterization of fault rocks from the Koyna deep drilling project (India)

In questa tesi magistrale vengono descritte le caratteristiche mineralogiche e microstrutturali di campioni di roccia di faglia prelevati dai pozzi di perforazione profonda dell’area di Koyna, India (https://www.icdp-online.org/projects/world/asia/koyna-india/). Questa area è di eccezionale rilevanza dal punto di vista dell’attività sismica indotta dall’uomo. Infatti, nel 1967, in questa zona con bassissima sismicità naturale, a seguito della realizzazione di un invaso nei primi anni ’60 del secolo scorso, venne registrato il più violento terremoto indotto da attività antropiche (magnitudo - ML= 6.3, 177 vittime). Dal punto di vista geologico la zona è caratterizzata fino a 2 km di profondità da una pila di colate laviche basaltiche appartenenti ai Deccan Traps, una provincia magmatica formatasi 65 Ma e che copre il sottostante basamento granitico Archeano (2.8 Ga). Il basamento ospita le fratture e le faglie riattivate dalle attività antropiche. Il progetto di perforazione comprende 9 pozzi che raggiungono una profondità massima di 3500 m, ed è mirato oltre all’installazione di sismometri e altri strumenti per la misura di deformazioni, temperature, ecc., anche al campionamento delle rocce di faglia del basamento. Grazie ad una collaborazione scientifica con il Prof. Sukanta Roy, leader del progetto di perforazione di Koyna, ed Elena Spagnuolo (INGV – Roma) abbiamo a disposizione 17 campioni di rocce di faglia. Gli obiettivi della tesi sono: (1) caratterizzazione mineralogica dei campioni di roccia tramite analisi con la tecnica di diffrazione da polveri a raggi X e (2) identificazione della successione di eventi deformativi (e in particolare dell’ultima fase associata alla riattivazione delle faglie causata dall’attività antropica) mediante microscopia ottica ed elettronica ad altissima risoluzione (FEG-SEM).This master's thesis describes the mineralogical and microstructural characteristics of fault rock samples taken from deep perforation boreholes in the Koyna area, India (https://www.icdp-online.org/projects/world/asia/koyna-india/). This area is of exceptional significance from the point of view of human-induced seismic activity. In fact, in 1967, in this area with very low natural seismicity, following the construction of a reservoir in the early 1960s, the most violent human-induced earthquake was recorded (magnitude - ML= 6.3, 177 casualties). Geologically, the area is characterized by 2 km thick basaltic lava flows belonging to the Deccan Traps, a magmatic province formed 65 Ma and covering the underlying Archean granitic basement (2.8 Ga). The basement hosts fractures and faults reactivated by anthropogenic activities. The drilling project includes 9 boreholes reaching a maximum depth of 3500 m, and is aimed not only at the installation of seismometers and other instruments for measuring deformation, temperature, etc., but also at sampling the basement fault rocks. Thanks to a scientific collaboration with Prof. Sukanta Roy, leader of the Koyna drilling project, and Elena Spagnuolo (INGV - Rome) we have at our disposal 17 samples of fault rocks. The objectives of the thesis are (1) mineralogical characterization of the rock samples by analysis with the X-ray powder diffraction technique and (2) identification of the succession of deformation events (and in particular of the last phase associated with the reactivation of faults caused by anthropogenic activity) by optical and ultra-high resolution electron microscopy (FEG-SEM)