To fulfill the requirements of the operation in a wide power range, a parallel configuration with modular power factor correctors (PFCs) is proposed. Each PFC module is composed of a bridge-rectifier, a fly-back converter and associated passive filters. The fly-back converter is independently operated at a fixed frequency with a discontinuous inductor current. This allows the modules to achieve a high power factor and to regulate the output power with simple control. With the same duty-ratio and frequency, the total current will be distributed equally to each operating module without complex current sharing control. The operating modules are equally phase-shifted to take the advantages of the continuous current mode when operated at a higher power. Experiments were conducted to achieve a power rating of 1 kVA by operating 10 PFC modules in parallel. The duty-ratio of the operating modules is controlled by a micro-controller to regulate the output power in accordance with the load requirement. A complex programmable logic device (CPLD) is used for phase-shifting. All modules are operated in turn to share the operating cycles in a more equal manner. Experimental results demonstrate the parallel configuration can achieve the expected performances.

Operating batteries in parallel is attempted to overcome the problems with conventionally used battery bank, in which batteries are connected in series. The problems and the management with the operation of serial connected batteries are first addressed. The related topics to the parallel configuration are reviewed. Then, the parallel configuration with battery power modules is proposed. The battery power module can be realized with different dc-to-dc converters for different applications. When batteries are charged in parallel, the problem of over-charge can be avoided. With parallel operation, the discharging currents of the batteries are independently controlled but are coordinated to execute a full amount load current. This allows for scheduling the discharging profiles under different operating conditions. As a result, a sophisticated discharging profile can be realized to utilize the available stored energy in batteries. On the other hand, some of the batteries may take rest or be isolated from the system for the detections at a time. This facilitates the estimations of the state of charge (SOC) and the state of health (SOH). Moreover, the completely exhausted or damaged batteries can be isolated from the battery power supply bank without interrupting the system operation. Experiments are carried out on battery power modules with lead-acid batteries incorporating with associated buck-boost converters. The experimental results demonstrate that a more efficient utilization of battery energy can be achieved. On the other hand, a more reasonable management can be done with simple estimation methods of the SOC and the SOH.

This works applies the idea of adjustment an engine-generator, so it is possible to connect an engine-generator, or other type of a generator, to the electricity. Consequently, the machine can transform the power supply without an outage. This work concerns the complex approach, provides the descriptions of particular parts, sensors and active components of a motor-generator and includes the explanation of their function. Further research is focused on designing and drawing a plan with a choice of a control unit for the whole system. Finally, the work deals with the complex implementation and testing the machine in real operation.

This thesis deals with the steady operation and short-circuit conditions in the 110 kV network E.ON in a separate and parallel operation of nodal areas of Otrokovice substation and Sokolnice substation. The theoretical part is devoted to the calculation of steady state high-voltage systems using Newton's iterative method, transient phenomena that may occur in the power system short-circuit calculations and theories. The practical part deals with the actual calculations of steady state and short-circuit conditions in a separate and parallel operation of nodal areas Sokolnice-Otrokovice, which were calculated using the dispatching program. These calculations are then evaluated for possible use of involvement in actual operation. At the end there are suggestions on operational measures in the network 110 kV.

This dissertation presents a systematic design and demonstration of a novel solid-state DC circuit breaker. The mechanical circuit breaker is widely used in power systems to protect industrial equipment during fault or abnormal conditions. Compared with the slow and high-maintenance mechanical circuit breaker, the solid-state circuit breaker is capable of high-speed interruption of high currents without generating an arc, hence it is maintenance-free. Both the switch and the tripping unit are solid-state, which meet the requirements of precise protection and high reliability. The major challenge in developing and adopting a solid-state circuit breaker has been the lack of power semiconductor switches that have adequate current-carrying capability and interruption capability. The high-speed, high-current solid-state DC circuit breaker proposed and demonstrated here uses a newly-emerging power semiconductor switch, the emitter turn-off (ETO) thyristor as the main interruption switch. In order to meet the requirement of being a high-current circuit breaker, ETO parallel operation is needed. Therefore the major effort of this dissertation is dedicated to the development of a high-current (5000A) DC switch module that utilizes multiple ETOs in parallel. This work can also be used to develop an AC switch module by changing the asymmetrical ETOs used to symmetrical ETOs. An accurate device model of the ETO is needed for the development of the high-current DC switch module. In this dissertation a novel physics-base lumped charge model is developed for the ETO thyristor for the first time. This model is verified experimentally and used for the research and development of the emitter turn-off (ETO) thyristor as well as the DC switch module discussed in this dissertation. With the aid of the developed device model, the device current sharing between paralleled multiple ETO thyristors is investigated. Current sharing is difficult to achieve for a thyristor-type device due to the large device parameter variations and strong positive feedback mechanism in a latched thyristor. The author proposes the "DirectETO" concept that directly benefits from the high-speed capability of the ETO and strong thermal couplings among ETOs. A high-current DC switch module based on the DirectETO can be realized by directly connecting ETOs in parallel without the bulky current sharing inductors used in other current-sharing solutions. In order to achieve voltage stress suppression under high current conditions, the parasitic parameters, especially parasitic inductance in a high-current ETO switch module are studied. The Partial Element Equivalent Circuit (PEEC) method is used to extract the parasitics. Combined with the developed device model, the electrical interactions among multiple ETOs are investigated which results in structural modification for the solid-state DC switch module. The electro-thermal model of the DC switch module and the heatsink subsystem is used to identify the "thermal runaway" phenomenon in the module that is caused by the negative temperature coefficient of the ETO's conduction drop. The comparative study of the electro-thermal coupling identifies a strongly-coupled thermal network that increases the stability of the thermal subsystem. The electro-thermal model is also used to calculate the DC and transient thermal limit of the DC switch module. The high-current (5000A) DC switch module coupled with a solid state tripping unit is successfully applied as a high-speed, high-current solid-state DC circuit breaker. The experimental demonstration of a 5000A current interruption shows an interruption time of about 5 microseconds. This high-speed, high-current DC switch module can therefore be used in DC circuit breaker applications as well as other types of application, such as AC circuit breakers, transfer switches and fault current limiters. Since the novel solid-state DC circuit breaker is able to extinguish the fault current even before it reaches an uncontrollable level, this feature provides a fast-acting, current-limiting protection scheme for power systems that is not possible with traditional circuit breakers. The potential impact on the power system is also discussed in this dissertation. / Ph. D.

雲端的盛行使得人們做任何事都要透過網路，但是總會有些有心人士使用一些惡意程式來創造攻擊或通過網絡連接竊取資料。為了防止這些網路惡意攻擊，我們必須不斷檢查網路流量資料，然而現在這個雲端時代，網路的資料是非常龐大且複雜，若要檢查所有網路資料不僅耗時而且非常沒有效率。 本研究使用TensorFlow與多個圖形處理器(Graphics Processing Unit, GPU)來實作類神經網路(Artificial Neural Networks, ANN)機制，用以分析網路流量資料，並得到一個可以判斷正常與異常網路流量的偵測規則，也設計一個實驗來驗證我們提出的類神經網路機制是否符合網路流向異常偵測的時效性和有效性。 在實驗過程中，我們發現使用更多的GPU可以減少訓練類神經網路的時間，並且在我們的實驗設計中使用三個GPU進行運算可以達到網路流量異常偵測的時效性。透過該方法得到的初步實驗結果，我們提出機制的結果優於使用反向傳播算法訓練類神經網路得到的結果。 / The prosperity of the cloud makes people do anything through the Internet, but there are people with bad intention to use some malicious programs to create attacks or steal information through the network connection. In order to prevent these cyber-attacks, we have to keep checking the network traffic information. However, in the current cloud environment, the network information is huge and complex that to check all the information is not only time-consuming but also inefficient. This study uses TensorFlow with multiple Graphic Processing Units (GPUs) to implement an Artificial Neural Networks (ANN) mechanism to analyze network traffic data and derive detection rules that can identify normal and malicious traffics, and we call it Network Traffic Anomaly Detection (NTAD). Experiments are also designed to verify the timeliness and effectiveness of the derived ANN mechanism. During the experiment, we found that using more GPUs can reduce training time, and using three GPUs to do the operation can meet the timeliness in NTAD. As a result of this method, the experiment result was better than ANN with back propagation mechanism.

This master’s thesis is divided into two logical parts. The first part contains theory of calculation of steady state and short-circuits conditions within 110 kV distribution network. Newton’s method and short-circuit current calculation is also explained here. It also deals with classification and aftereffects of transient performance occurring in power networks. The second part contains practical calculation of steady flow and short-circuit conditions at parallel operation of transformers T403 and T402 in 400/110 kV transformer stations Sokolnice and Otrokovice. This calculation is done with program used by system operators called SINAUT Spectrum and consequently analyzed. This part also contains brief description of substations from this region.

IGBTs are today’s most important power-semiconductor switches in the field of medium and high power ranges. The good controllability of this device with a voltage source is advantageous. The following work investigates the IGBT at short-circuit and surge-current condition. A particular focus is put on the IGBT’s feedback on the gate-control circuit. Special modes during the short circuit are measured and explained. For example the self-turn-off mechanism during short circuit and the collector-emitter voltage-clamping capability during fast short-circuit turn-off. Measurements are done at high-voltage IGBT chips and press-pack devices. The complete IGBT output characteristic up to the breakdown point is measured. Additionally, the short circuit is investigated at the parallel and series connection of IGBTs. Supporting semiconductor simulations of a high-voltage IGBT model, that was specially constructed for this work, analyse the internal behaviour during the mentioned conditions. The impact of different IGBT designs on the short-circuit ruggedness and breakdown behaviour is shown. Solutions for protecting the device from destruction during overload condition are presented. Measurements and simulations explain the surge-current capability of an IGBT and demonstrate the benefit for the application. / IGBTs gehören zu den wichtigsten Halbleiter-Leistungsbauelementen im mittleren und oberen Leistungsbereich. Die einfache Ansteuerbarkeit durch eine Spannungsquelle ist dabei von großem Vorteil. Nachfolgende Untersuchungen beschäftigen sich mit dem IGBT-Kurzschluss und -Stoßstrom. Ein besonderes Augenmerk wird auf die Rückwirkung des IGBTs auf den Ansteuerkreis gelegt. Spezielle IGBT Modi werden gemessen und erklärt. Hierzu zählen zum Beispiel der Self-Turn-Off Mechanismus während des Kurzschlusses und die selbständige Kollektor-Emitter Spannungsbegrenzung während schnellen Kurzschlussabschaltens. Hierfür werden Messungen an Hochspannungs-IGBT Chips und Press-Pack IGBTs durchgeführt. Des Weiteren wird das komplette Ausgangskennlinienfeld des IGBTs vermessen und das Kurzschlussverhalten in der Parallel- und Reihenschaltung untersucht. Halbleitersimulationen eines Hochspannungs-IGBT Modells zeigen das interne IGBT Verhalten und unterstützen die Analyse der Messungen. Der Einfluss unterschiedlicher IGBT Designs in Bezug auf die Kurzschluss-Robustheit und das Durchbruchverhalten wird aufgezeigt. Möglichkeiten zum Schutz des IGBTs vor Zerstörung werden erörtert. Messungen und Simulationen zeigen die gute Stoßstromfestigkeit von IGBTs bei erhöhter Gatespannung auf. Davon kann die komplette Anwendung profitieren.

In the modern generation, Electric Power has become one of the fundamental needs for humans to survive. This is due to the dependence of continuous availability of power. However, for electric power to be available to the society, it has to pass through a number of complex stages. Through each stage power quality problems are experienced on the grid. Under-voltages and over-voltages are the most common electric problems experienced on the grid, causing industries and business firms losses of Billions of dollars each year. Researchers from different regions are attracted by an idea that will overcome all the electrical issues experienced in the traditional grid using Artificial Intelligence (AI). The idea is said to provide electric power that is sustainable, economical, reliable and efficient to the society based on Evolutionary Algorithms (EAs). The idea is Smart Grid. The research focused on Power Quality Optimization in Smart Grid based on improved Differential Evolution (DE), with the objective functions to minimize voltage swells, counterbalance voltage sags and eliminate voltage surges or spikes, while maximizing the power quality. During Differential Evolution improvement research, elimination of stagnation, better and fast convergence speed were achieved based on modification of DE’s mutation schemes and parameter control selection. DE/Modi/2 and DE/Modi/3 modified mutation schemes proved to be the excellent improvement for DE algorithm by achieving excellent optimization results with regards to convergence speed and elimination of stagnation during simulations. The improved DE was used to optimize Power Quality in smart grid in combination with the reconfigured and modified Dynamic Voltage Restorer (DVR). Excellent convergence results of voltage swells and voltage sags minimization were achieved based on application of multi-objective parallel operation strategy during simulations. MATLAB was used to model the proposed solution and experimental simulations. / Electrical and Mining Engineering / M. Tech. (Electrical Engineering)

IGBTs are today’s most important power-semiconductor switches in the field of medium and high power ranges. The good controllability of this device with a voltage source is advantageous. The following work investigates the IGBT at short-circuit and surge-current condition. A particular focus is put on the IGBT’s feedback on the gate-control circuit. Special modes during the short circuit are measured and explained. For example the self-turn-off mechanism during short circuit and the collector-emitter voltage-clamping capability during fast short-circuit turn-off. Measurements are done at high-voltage IGBT chips and press-pack devices. The complete IGBT output characteristic up to the breakdown point is measured. Additionally, the short circuit is investigated at the parallel and series connection of IGBTs. Supporting semiconductor simulations of a high-voltage IGBT model, that was specially constructed for this work, analyse the internal behaviour during the mentioned conditions. The impact of different IGBT designs on the short-circuit ruggedness and breakdown behaviour is shown. Solutions for protecting the device from destruction during overload condition are presented. Measurements and simulations explain the surge-current capability of an IGBT and demonstrate the benefit for the application. / IGBTs gehören zu den wichtigsten Halbleiter-Leistungsbauelementen im mittleren und oberen Leistungsbereich. Die einfache Ansteuerbarkeit durch eine Spannungsquelle ist dabei von großem Vorteil. Nachfolgende Untersuchungen beschäftigen sich mit dem IGBT-Kurzschluss und -Stoßstrom. Ein besonderes Augenmerk wird auf die Rückwirkung des IGBTs auf den Ansteuerkreis gelegt. Spezielle IGBT Modi werden gemessen und erklärt. Hierzu zählen zum Beispiel der Self-Turn-Off Mechanismus während des Kurzschlusses und die selbständige Kollektor-Emitter Spannungsbegrenzung während schnellen Kurzschlussabschaltens. Hierfür werden Messungen an Hochspannungs-IGBT Chips und Press-Pack IGBTs durchgeführt. Des Weiteren wird das komplette Ausgangskennlinienfeld des IGBTs vermessen und das Kurzschlussverhalten in der Parallel- und Reihenschaltung untersucht. Halbleitersimulationen eines Hochspannungs-IGBT Modells zeigen das interne IGBT Verhalten und unterstützen die Analyse der Messungen. Der Einfluss unterschiedlicher IGBT Designs in Bezug auf die Kurzschluss-Robustheit und das Durchbruchverhalten wird aufgezeigt. Möglichkeiten zum Schutz des IGBTs vor Zerstörung werden erörtert. Messungen und Simulationen zeigen die gute Stoßstromfestigkeit von IGBTs bei erhöhter Gatespannung auf. Davon kann die komplette Anwendung profitieren.