On Deep Machine Learning Based Techniques for Electric Power Systems

This thesis provides deep machine learning-based solutions to real-time mitigation of power quality disturbances such as flicker, voltage dips, frequency deviations, harmonics, and interharmonics using active power filters (APF). In an APF the processing delays reduce the performance when the disturbance to be mitigated is tima varying. The the delays originate from software (response time delay) and hardware (reaction time delay). To reduce the response time delays of APFs, this thesis propose and investigate several different techniques. First a technique based on multiple synchronous reference frame (MSRF) and order-optimized exponential smoothing (ES) to decrease the settling time delay of lowpass filtering steps. To reduce the computational time, this method is implemented in a parallel processing using a graphics processing unit (GPU) to estimate the time-varying harmonics and interharmonics of currents. Furthermore, the MSRF and three machine learning-based solutions are developed to predict future values of voltage and current in electric power systems which can mitigate the effects of the response and reaction time delays of the APFs. In the first and second solutions, a Butterworth filter is used to lowpass filter the\ua0 dq\ua0 components, and linear prediction and long short-term memory (LSTM) are used to predict the filtered\ua0 dq\ua0 components. The third solution is an end-to-end ML-based method developed based on a combination of convolutional neural networks (CNN) and LSTM. The Simulink implementation of the proposed ML-based APF is carried out to compensate for the current waveform harmonics, voltage dips, and flicker in Simulink environment embedded AI computing system Jetson TX2.\ua0In another study, we propose Deep Deterministic Policy Gradient (DDPG), a reinforcement learning (RL) method to replace the controller loops and estimation blocks such as PID, MSRF, and lowpass filters in grid-forming inverters. In a conventional approach it is well recognized that the controller tuning in the differen loops are difficult as the tuning of one loop influence the performance in other parts due to interdependencies.In DDPG the control policy is derived by optimizing a reward function which measure the performance in a data-driven fashion based on extensive experiments of the inverter in a simulation environment.\ua0Compared to a PID-based control architecture, the DDPG derived control policy leads to a solution where the response and reaction time delays are decreased by a factor of five in the investigated example.\ua0Classification of voltage dips originating from cable faults is another topic addressed in this thesis work. The Root Mean Square (RMS) of the voltage dips is proposed as preprocessing step to ease the feature learning for the developed\ua0 LSTM based classifier. Once a cable faults occur, it need to be located and repaired/replaced in order to restore the grid operation. Due to the high importance of stability in the power generation of renewable energy sources, we aim to locate high impedance cable faults in DC microgrid clusters which is a challenging case among different types of faults. The developed Support Vector Machine (SVM) algorithm process the maximum amplitude and\ua0 di/dt\ua0 of the current waveform of the fault as features, and the localization task is carried out with\ua0 95 %\ua0 accuracy.\ua0Two ML-based solutions together with a two-step feature engineering method are proposed to classify Partial Discharges (PD) originating from pulse width modulation (PWM) excitation in high voltage power electronic devices. As a first step, maximum amplitude, time of occurrence, area under PD curve, and time distance of each PD are extracted as features of interest. The extracted features are concatenated to form patterns for the ML algorithms as a second step. The suggested feature classification using the proposed ML algorithms resulted in\ua0 95.5 %\ua0 and\ua0 98.3 %\ua0\ua0 accuracy on a test data set using ensemble bagged decision trees and LSTM networks

Анализ гармонического состава токов и напряжений дуг в дуговой сталеплавильной печи с использованием математической модели

This paper analyzes how the relative effective total odd and even current and voltage harmonics of an electric arc in a furnace correlate with the thermal time constant of the arc, with the valve effect, and with the asymmetrical operation. The furnace circuit model was used to theorize upon the effectiveness of using even harmonics data to diagnose the charge melting stage during initial melting; and odd harmonics to analyze the late stages. The results of mathematical modeling helped draw guidelines for the design of the charge melting diagnosis unit to be part of the electrical parameters control system; the unit design depends on the furnace type. The results could be of use in research of better control algorithms for electric arc furnaces and lade furnaces with a focus on reducing the energy costs of producing molten steel.В рамках данного исследования выполнен анализ зависимости относительных действующих значений суммарных чётных и нечётных гармоник токов и напряжений электрических дуг дуговой сталеплавильной печи от величины тепловой постоянной времени дуги, вентильного эффекта, а также несимметричных режимов. С использованием математической модели электрического контура печи теоретически обоснована эффективность применения информации о чётных гармониках для решения задач диагностики стадии плавления шихты на начальной стадии расплавления и нечётных гармониках на стадии доводки. На базе полученных в ходе математического моделирования результатов сформированы рекомендации по формированию структуры блока диагностики стадии плавления металлошихты в составе системы управления электрическим режимом в зависимости от типа электросталеплавильного агрегата. Полученные результаты обладают потенциалом к применению в исследованиях, направленных на разработку усовершенствованных алгоритмов управления электрическим режимом дуговых сталеплавильных печей и установок ковш-печь с целью снижения энергозатрат на производство жидкой стали

Malzeme Üretiminde Siber Güvenlik

Industry 4.0, a new industry revolution, is happening now and several developed countries are leading the path. Internet of things (IoT) is also encompassed by Industry 4.0. In the future, more devices in factories are to be connected to Ethernet or Internet. However, this makes the companies, devices and researchers vulnerable to cyber-attacks. Recently, some cyber-attacks which have happened to some companies or countries verify the danger. Sintering systems and furnaces are used for research by universities and for series manufacturing by factories. Arc furnaces and induction furnaces are also commonly used devices in metal factories. A sintering system, an arc furnace or an induction furnace which is connected to Internet or Ethernet may also be under cyber-attack threat. The danger may be prevented by taking necessary precautions. In this study, these threeproduction systems are first briefly introduced and then inspected assuming that they have been connected to internet and examined with considering cyber-attack point of view. Some basic solutions against cyber-attacks to the aforementioned devices are suggested.Yeni bir endüstri devrimi olan Endüstri 4.0 günümüzde yaşanmakta ve özellikle bazı gelişmiş ülkeler bu_x000D_ alanda öncü çalışmalar ortaya koymaktadır. Nesnelerin İnterneti (IoT) Endüstri 4.0 tarafından kapsanan önemli_x000D_ bir altyapıdır. Gelecekte, fabrikalardaki daha fazla cihazın Ethernet veya İnternet üzerinden çalışmalarını_x000D_ sürdürmesi öngörülmektedir. Bunun kurum ve fabrika ortamındaki cihazları ve verileri siber saldırılara karşı_x000D_ savunmasız bırakabileceği açıktır. Son zamanlarda, farklı ülkelerden farklı kurumlarda yapılan bazı siber_x000D_ saldırılar tehlikeyi doğrulamaktadır. Çeşitli malzeme sinterleme sistemleri ve fırınlar üniversiteler tarafından_x000D_ araştırma yapmak ve fabrikalar tarafından seri imalat yapmak için kullanılırlar. Ark fırınları ve endüksiyon_x000D_ fırınları da metal fabrikalarında yaygın olarak kullanılan cihazlardır. Internet veya ethernet'e bağlı bir sinterleme_x000D_ sistemi, bir ark ocağı veya bir indüksiyon ocağı da siber saldırı tehdidi altında olabilir. Bu noktada gerekli_x000D_ önlemler alınarak tehlike önlenebilir. Bu çalışmada, bu üç üretim sistemi ilk öncelikle kısaca tanıtılmış ve daha_x000D_ sonra internete bağlı oldukları dikkate alınarak siber saldırı bakış açıları ile incelenmişlerdir. Çalışmada,_x000D_ belirtilen cihazlara karşı olası siber saldırılara yönelik çözümler önerilmektedir.Yeni bir endüstri devrimi olan Endüstri 4.0 günümüzde yaşanmakta ve özellikle bazı gelişmiş ülkeler bu alanda öncü çalışmalar ortaya koymaktadır. Nesnelerin İnterneti (IoT) Endüstri 4.0 tarafından kapsanan önemli bir altyapıdır. Gelecekte, fabrikalardaki daha fazla cihazın Ethernet veya İnternet üzerinden çalışmalarını sürdürmesi öngörülmektedir. Bunun kurum ve fabrika ortamındaki cihazları ve verileri siber saldırılara karşı savunmasız bırakabileceği açıktır. Son zamanlarda, farklı ülkelerden farklı kurumlarda yapılan bazı siber saldırılar tehlikeyi doğrulamaktadır. Çeşitli malzeme sinterleme sistemleri ve fırınlar üniversiteler tarafından araştırma yapmak ve fabrikalar tarafından seri imalat yapmak için kullanılırlar. Ark fırınları ve endüksiyon fırınları da metal fabrikalarında yaygın olarak kullanılan cihazlardır. Internet veya ethernet'e bağlı bir sinterleme sistemi, bir ark ocağı veya bir indüksiyon ocağı da siber saldırı tehdidi altında olabilir. Bu noktada gerekli önlemler alınarak tehlike önlenebilir. Bu çalışmada, bu üç üretim sistemi ilk öncelikle kısaca tanıtılmış ve daha sonra internete bağlı oldukları dikkate alınarak siber saldırı bakış açıları ile incelenmişlerdir. Çalışmada, belirtilen cihazlara karşı olası siber saldırılara yönelik çözümler önerilmektedir

Power Quality

Electrical power is becoming one of the most dominant factors in our society. Power generation, transmission, distribution and usage are undergoing signifi cant changes that will aff ect the electrical quality and performance needs of our 21st century industry. One major aspect of electrical power is its quality and stability – or so called Power Quality. The view on Power Quality did change over the past few years. It seems that Power Quality is becoming a more important term in the academic world dealing with electrical power, and it is becoming more visible in all areas of commerce and industry, because of the ever increasing industry automation using sensitive electrical equipment on one hand and due to the dramatic change of our global electrical infrastructure on the other. For the past century, grid stability was maintained with a limited amount of major generators that have a large amount of rotational inertia. And the rate of change of phase angle is slow. Unfortunately, this does not work anymore with renewable energy sources adding their share to the grid like wind turbines or PV modules. Although the basic idea to use renewable energies is great and will be our path into the next century, it comes with a curse for the power grid as power fl ow stability will suff er. It is not only the source side that is about to change. We have also seen signifi cant changes on the load side as well. Industry is using machines and electrical products such as AC drives or PLCs that are sensitive to the slightest change of power quality, and we at home use more and more electrical products with switching power supplies or starting to plug in our electric cars to charge batt eries. In addition, many of us have begun installing our own distributed generation systems on our rooft ops using the latest solar panels. So we did look for a way to address this severe impact on our distribution network. To match supply and demand, we are about to create a new, intelligent and self-healing electric power infrastructure. The Smart Grid. The basic idea is to maintain the necessary balance between generators and loads on a grid. In other words, to make sure we have a good grid balance at all times. But the key question that you should ask yourself is: Does it also improve Power Quality? Probably not! Further on, the way how Power Quality is measured is going to be changed. Traditionally, each country had its own Power Quality standards and defi ned its own power quality instrument requirements. But more and more international harmonization efforts can be seen. Such as IEC 61000-4-30, which is an excellent standard that ensures that all compliant power quality instruments, regardless of manufacturer, will produce of measurement instruments so that they can also be used in volume applications and even directly embedded into sensitive loads. But work still has to be done. We still use Power Quality standards that have been writt en decades ago and don’t match today’s technology any more, such as fl icker standards that use parameters that have been defi ned by the behavior of 60-watt incandescent light bulbs, which are becoming extinct. Almost all experts are in agreement - although we will see an improvement in metering and control of the power fl ow, Power Quality will suff er. This book will give an overview of how power quality might impact our lives today and tomorrow, introduce new ways to monitor power quality and inform us about interesting possibilities to mitigate power quality problems. Regardless of any enhancements of the power grid, “Power Quality is just compatibility” like my good old friend and teacher Alex McEachern used to say. Power Quality will always remain an economic compromise between supply and load. The power available on the grid must be suffi ciently clean for the loads to operate correctly, and the loads must be suffi ciently strong to tolerate normal disturbances on the grid

Анализ качества электроэнергии при стабилизации активной мощности дуговой сталеплавильной печи с помощью статического тиристорного компенсатора

The paper presents the key findings of studying the quality of electricity at the buses of an electric steel-making complex as affected by a static var compensator (SVC) running a novel control algorithm designed to improve the electric performance of an electric arc furnace (EAF) by stabilizing its active power at an optimal value. Analysis of how an SVC runs this algorithm reveals a considerable degradation of voltage quality compared to experiments with conventional algorithms. For detailed evaluation of SVC effects on the quality of electricity (QE), the research team ran an SVC in active-power mode and computed the QE values characterizing slow voltage deviations, non-sinusoidality, imbalance, and fluctuation; the values were compared against those attained by the reactive power- or voltage-controlled compensator. Experimentation used the mathematical model of an existing EAF-120-SVC unit, which was developed and run in MATLAB Simulink. To enable the SVC to sustain a constant active EAF power while also keeping the QE values sufficiently high, the paper proposes a structure of additional voltage and reactive power coefficient constraints, voltage balancing, and flicker suppression.Приведены основные результаты исследования качества электроэнергии на шинах электросталеплавильного комплекса в случае работы статического тиристорного компенсатора (СТК) по новому алгоритму управления, предназначенному для улучшения электрических характеристик дуговой сталеплавильной печи (ДСП) за счет стабилизации ее активной мощности на оптимальном уровне. Анализ особенностей работы СТК в данном режиме показал значительное ухудшение характеристик напряжения по сравнению с опытами, в которых компенсатор функционировал по классическим алгоритмам. Для проведения подробной оценки негативного влияния СТК на качество электроэнергии (КЭ) при его работе по активной мощности рассчитаны показатели КЭ, характеризующие медленные изменения, несинусоидальность, несимметрию и колебания напряжения, и проведено их сравнение с результатами экспериментов с управлением компенсатора по реактивной мощности и напряжению. Опыты проводились на математической модели действующего электросталеплавильного комплекса «ДСП-120-СТК», разработанной в приложении Simulink математического пакета MATLAB. Для обеспечения требуемых значений показателей КЭ при функционировании СТК в режиме поддержания постоянной активной мощности ДСП разработаны структуры дополнительных блоков ограничения по напряжению и коэффициенту реактивной мощности, симметрирования напряжений и подавления фликера

Impedance analysis of harmonic resonance in HVDC connected Wind Power Plants

During the last years the development of HVDC connected offshore wind power plants increased. As the first wind farms of this type were commissioned, an unexpected phenomenon occurred. Electrical harmonic resonance in offshore AC grid led to outages of the HVDC transmission system. The thesis introduces the phenomenon and compare different methods of its analysis. The study focuses on harmonic frequencies identification excited through the resonance phenomena between the elements within WPP's inner AC network. The analysis includes observations from three tested topology cases by different methods: frequency sweep and harmonic resonance modal analysis. The comparison is performed for diverse converter models: voltage source based, current source based and nonlinear impedance model obtained by harmonic linearization method. The results of the analysis are verified by the outcome attained in DIgSILENT Power Factory software. The study also includes the stability analysis based on Nyquist criterion and interpreted in Bode diagrams. Furthermore, the result of investigation exposes the clues for possible subsequent implementation of harmonic filters as well as for beneficial control of converters. Feasible measures for resonance mitigation from literature are described and proposed