Voltage Dip mitigation in Distribution System by Using D-Statcom

A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure or a mis-operation of end user equipments. Utility distribution networks, sensitive industrial loads and critical commercial operations suffer from various types of outages and service interruptions which can cost significant financial losses. With the restructuring of power systems and with shifting trend towards distributed and dispersed generation, the issue of power quality is going to take newer dimensions. In developing countries like India, where the variation of power frequency and many such other determinants of power quality are themselves a serious question, it is very vital to take positive steps in this direction .The present work is to identify the prominent concerns in this area and hence the measures that can enhance the quality of the power are recommended. This work describes the techniques of correcting the supply voltage sag, swell and interruption in a distributed system. At present, a wide range of very flexible controllers, which capitalize on newly available power electronics components, are emerging for custom power applications. Among these, the distribution static compensator and the dynamic voltage restorer are most effective devices, both of them based on the VSC principle. A D-STATCOM injects a current into the system to correct the voltage sag, swell and interruption. Comprehensive results are presented to assess the performance of each device as a potential custom power solution The STATCOM is applied to regulate transmission voltage to allow greater power flow in a voltage limited transmission network, in the same manner as a static var compensator (SVC), the STATCOM has further potential by giving an inherently faster response and greater output to a system with depressed voltage and offers improved quality of supply. The main applications of the STATCOM are; Distribution STATCOM (D-STATCOM) exhibits high speed control of reactive power to provide voltage stabilization and other type of system control. The DSTATCOM protects the utility transmission or distribution system from voltage sag and /or flicker caused by rapidly varying reactive current demand. During the transient conditions the D-STATCOM provides leading or lagging reactive power to active system stability, power factor correction and load balancing Keywords: Distribution Static Synchronous Compensator (D-STATCOM), Voltage Dip, Distribution Syste

Incremental learning for large-scale stream data and its application to cybersecurity

As many human currently depend on technologies to assist with daily tasks, there are more and more applications which have been developed to be fit in one small gadget such as smart phone and tablet. Thus, by carrying this small gadget alone, most of our tasks are able to be settled efficiently and fast. Until the end of 20th century, mobile phones are only used to call and to send short message service (sms). However, in early 21st century, a rapid revolution of communi�cation technology from mobile phone into smart phone has been seen in which the smart phone is equipped by 4G Internet line along with the telephone service provider line. Thus, the users are able to make a phone call, send messages using variety of application such as Whatsapp and Line, send email, serving websites, accessing maps and handling some daily tasks via online using online banking, online shopping and online meetings via video conferences. In previous years, if there are cases of missing children or missing cars, the victims would rely on the police investigation. But now, as easy as uploading a notification about the loss on Facebook and spread the news among Facebook users, there are more people are able to help in the search. Despite the advantages that can be obtained using these technologies, there are a group of irresponsible people who take advan�tage of current technologies for their own self-interest. Among the applications that are usually being used by almost Internet users and also are often misused by cyber criminals are email and websites. Therefore, we take this initiative to make enhancement in cyber security application to avoid the Internet users from being trapped and deceived by the trick of cyber criminals by developing detec�tion system of malicious spam email and Distributed Denial of Services (DDoS) 377$3(53867$.1781.8781$0,1$+ iii backscatter. Imagine that a notice with a logo of Mobile Phone company is received by an email informing that the customer had recently run up a large mobile phone bill. A link regarding the bill is attached for him/her to find out the details. Since, the customer thinks that the billing might be wrong, thus the link is clicked. However, the link is directed to a webpage which displays a status that currently the webpage is under construction. Then the customer closes the page and thinking of to visit the website again at other time. Unfortunately, after a single click actually a malicious file is downloaded and installed without the customer aware of it. That malicious file most probably is a Trojan that capable to steal confidential information from victim’s computer. On the next day, when the same person is using the same computer to log in the online banking, all of a sudden find out that his/her money is lost totally. This is one of a worst case scenario of malicious spam email which is usually handled by cybersecurity field. Another different case of cybersecurity is the Distributed Denial of Services (DDoS) attack. Let say, Company X is selling flowers via online in which the market is from the local and international customer. The online business of Company X is running normally as usual, until a day before mother’s day, the webpage of Company X is totally down and the prospective customers could not open the webpage to make order to be sent specially for their beloved mother. Thus, the customers would search another company that sells the same item. The Company X server is down, most probably because of the DDoS attack where a junk traffic is sent to that company server which makes that server could not serve the request by the legitimate customers. This attack effect not only the profit of the company, but also reputation damage, regular customer turnover and productivity decline. Unfortunately, it is difficult for a normal user like us to detect malicious spam 377$ 3(53867$.1781.8781$0,1$+ email or DDoS attack with naked eyes. It is because recently the spammers and attacker had improved their strategy so that the malicious email and the DDoS packets are hardly able to be differentiated with the normal email and data packets. Once the Social Engineering is used by the spammers to create relevant email content in the malicious spam email and when a new campaign of DDoS attack is launched by the attacker, no normal users are capable to distinguish the benign and malicious email or data packets. This is where my Ph.D project comes in handy. My Ph.d is focusing on constructing a detection system of malicious spam email and DDoS attack using a large number of dataset which are obtained by a server that collect double-bounce email and darknet for malicious spam email detection system and DDoS backscatter detection system, respectively. As many up-to-date data are used during the learning, the detection system would become more robust to the latest strategy of the cybercriminal. Therefore, the scenario mentioned above can be avoided by assisting the user with important information at the user-end such as malicious spam email filter or at the server firewall. First of all, the method to learn large-scale stream data must be solved before implementing it in the detection system. Therefore, in Chapter 2, the general learning strategy of large-scale data is introduced to be used in the cybersecurity applications which are discussed in Chapter 3 and Chapter 4, respectively. One of a critical criterion of the detection system is capable to learn fast because after the learning, the updated information needs to be passed to user to avoid the user from being deceived by the cybercriminal. To process large-scale data sequences, it is important to choose a suitable learning algorithm that is capable to learn in real time. Incremental learning has an ability to process large data in chunk and update the parameters after learning each chunk. Such type of learning keep and update only the minimum information on a classifier model. 377$3(53867$.1781.8781$0,1$+ Therefore, it requires relatively small memory and short learning time. On the other hand, batch learning is not suitable because it needs to store all training data, which consume a large memory capacity. Due to the limited memory, it is certainly impossible to process online large-scale data sequences using the batch learning. Therefore, the learning of large-scale stream data should be conducted incrementally. This dissertation contains of five chapters. In Chapter 1, the concept of in�cremental learning is briefly described and basic theories on Resource Allocating Network (RAN) and conventional data selection method are discussed in this chapter. Besides that, the overview of this dissertation is also elaborated in this chapter. In Chapter 2, we propose a new algorithm based on incremental Radial Basis Function Network (RBFN) to accelerate the learning in stream data. The data sequences are represented as a large chunk size of data given continuously within a short time. In order to learn such data, the learning should be carried out incrementally. Since it is certainly impossible to learn all data in a short pe�riod, selecting essential data from a given chunk can shorten the learning time. In our method, we select data that are located in untrained or “not well-learned” region and discard data at trained or “well-learned” region. These regions are represented by margin flag. Each region is consisted of similar data which are near to each other. To search the similar data, the well-known LSH method pro�posed by Andoni et al. is used. The LSH method indeed has proven be able to quickly find similar objects in a large database. Moreover, we utilize the LSH ʼs properties; hash value and Hash Table to further reduced the processing time. A flag as a criterion to decide whether to choose or not the training data is added in the Hash Table and is updated in each chunk sequence. Whereas, the hash value of RBF bases that is identical with the hash value of the training data is used to select the RBF bases that is near to the training data. The performance results of 377$ 3(53867$.1781.8781$0,1$+ vi the numerical simulation on nine UC Irvine (UCI) Machine Learning Repository datasets indicate that the proposed method can reduce the learning time, while keeping the similar accuracy rate to the conventional method. These results indi�cate that the proposed method can improve the RAN learning algorithm towards the large-scale stream data processing. In Chapter 3, we propose a new online system to detect malicious spam emails and to adapt to the changes of malicious URLs in the body of spam emails by updating the system daily. For this purpose, we develop an autonomous system that learns from double-bounce emails collected at a mail server. To adapt to new malicious campaigns, only new types of spam emails are learned by introducing an active learning scheme into a classifier model. Here, we adopt Resource Allocating Network with Locality Sensitive Hashing (RAN-LSH) as a classifier model with data selection. In this data selection, the same or similar spam emails that have already been learned are quickly searched for a hash table using Locally Sensitive Hashing, and such spam emails are discarded without learning. On the other hand, malicious spam emails are sometimes drastically changed along with a new arrival of malicious campaign. In this case, it is not appropriate to classify such spam emails into malicious or benign by a classifier. It should be analyzed by using a more reliable method such as a malware analyzer. In order to find new types of spam emails, an outlier detection mechanism is implemented in RAN-LSH. To analyze email contents, we adopt the Bag-of-Words (BoW) approach and generate feature vectors whose attributes are transformed based on the normalized term frequency-inverse document frequency. To evaluate the developed system, we use a dataset of double-bounce spam emails which are collected from March 1, 2013 to May 10, 2013. In the experiment, we study the effect of introducing the outlier detection in RAN-LSH. As a result, by introducing the outlier detection, we confirm that the detection accuracy is enhanced on 377$3(53867$.$$1781.8781$0,1$+ average over the testing period. In Chapter 4, we propose a fast Distributed Denial of Service (DDoS) backscat�ter detection system to detect DDoS backscatter from a combination of protocols and ports other than the following two labeled packets: Transmission Control Protocol (TCP) Port 80 (80/TCP) and User datagram Protocol (UDP) Port 53 (53/UDP). Usually, it is hard to detect DDoS backscatter from the unlabeled packets, where an expert is needed to analyze every packet manually. Since it is a costly approach, we propose a detection system using Resource Allocating Network (RAN) with data selection to select essential data. Using this method, the learning time is shorten, and thus, the DDoS backscatter can be detected fast. This detection system consists of two modules which are pre-processing and classifier. With the former module, the packets information are transformed into 17 feature-vectors. With the latter module, the RAN-LSH classifier is used, where only data located at untrained region are selected. The performance of the proposed detection system is evaluated using 9,968 training data from 80/TCP and 53/UDP, whereas 5,933 test data are from unlabeled packets which are col�lected from January 1st, 2013 until January 20th, 2014 at National Institute of Information and Communications Technology (NICT), Japan. The results indi�cate that detection system can detect the DDoS backscatter from both labeled and unlabeled packets with high recall and precision rate within a short time. Finally, in Chapter 5, we discussed the conclusions and the future work of our study: RAN-LSH classifier, malicious spam email detection system and DDoS backscatter detection system

Power quality and electromagnetic compatibility: special report, session 2

The scope of Session 2 (S2) has been defined as follows by the Session Advisory Group and the Technical Committee: Power Quality (PQ), with the more general concept of electromagnetic compatibility (EMC) and with some related safety problems in electricity distribution systems. Special focus is put on voltage continuity (supply reliability, problem of outages) and voltage quality (voltage level, flicker, unbalance, harmonics). This session will also look at electromagnetic compatibility (mains frequency to 150 kHz), electromagnetic interferences and electric and magnetic fields issues. Also addressed in this session are electrical safety and immunity concerns (lightning issues, step, touch and transferred voltages). The aim of this special report is to present a synthesis of the present concerns in PQ&EMC, based on all selected papers of session 2 and related papers from other sessions, (152 papers in total). The report is divided in the following 4 blocks: Block 1: Electric and Magnetic Fields, EMC, Earthing systems Block 2: Harmonics Block 3: Voltage Variation Block 4: Power Quality Monitoring Two Round Tables will be organised: - Power quality and EMC in the Future Grid (CIGRE/CIRED WG C4.24, RT 13) - Reliability Benchmarking - why we should do it? What should be done in future? (RT 15

A Novel Intelligent Neural Network Techniques of UPQC with Integrated Solar PV System for Power Quality Enhancement

A Novel, Intelligent control of a Unified Power Quality Conditioner (UPQC), coupled with a Photovoltaic (PV) system, is proposed in this work. It enhances the decarbonizes clean energy generation and maintains Power Quality (PQ) to the grid. In PV integrated UPQC, Crow Search Algorithm (CSA) assisted Perturb and Observation (P&O) Maximum Power Point Tracking (MPPT) technique. A d-q theory-based control is employed with the assistance of a Proportional Integral (PI) controller for controlling the working of UPQC and maintaining the power quality. The dynamic working of the PV-based UPQC is evaluated based on simulation outcomes attained from MATLAB

Application of Unified Power Flow Controller to Improve the Performance of Wind Energy Conversion System

This research introduces the unified power flow controller (UPFC) as a means to improve the overall performance of wind energy conversion system (WECS) through the development of an appropriate control algorithm. Also, application of the proposed UPFC control algorithm has been extended in this research to overcome some problems associated with the internal faults associated with WECS- voltage source converter (VSC), such as miss-fire, fire-through and dc-link faults

A Review on Power Quality Improvement via Custom Power Devices

Power Quality has been said a set of electrical boundaries of the electrical supply provided under normal operating condition that allow equipment to function in its rated condition without significant loss of performance and life expectancy that do not disturb or disrupt the consumers\u27 process. Performance degradation results when the electrical power supplied to equipment is deficient. Thus power quality improvement is the main concern of present era. The problems of power quality are rising exponentially from the last few decades due to the rising demand for power and the need for their improvement is indeed a big question. The main power quality problems such as voltage sags and swells, power interruptions (short and long), voltage spike, harmonic distortion, noise have led to financial losses. To avoid huge losses and to overcome the above mentioned problems, power electronics has evolved with its new types of devices known as Custom Power Devices which are being reviewed in this paper

Unified Power Quality Conditioner: protection and performance enhancement

The proliferation of power electronics-based equipment has produced a significant impact on the quality of electric power supply. Nowadays, much of the equipment is based on power electronic devices, often leading to problems of power quality. At the same time this equipment is typically equipped with microprocessor-based controllers which are quite sensitive to deviations from the ideal sinusoidal line voltage. Conventional power quality mitigation equipment is proving to be inadequate for an increasing number of applications, and this fact has attracted the attention of power engineers to develop dynamic and adjustable solutions to power quality problems. One modern and very promising solution that deals with both load current and supply voltage imperfections is the Unified Power Quality Conditioner (UPQC). This thesis investigates the development of UPQC protection scheme and control algorithms for enhanced performance. This work is carried out on a 12 kVA prototype UPQC. In order to protect the series inverter of the UPQC from overvoltage and overcurrent during short circuits on the load side of the UPQC, the secondary of the series transformer has to be short-circuited in a reasonably short time (microseconds). A hardware-based UPQC protection scheme against the load side short circuits is derived and its implementation and effectiveness is investigated. The main protection element is a crowbar connected across the secondary of the series transformer and consisting of a pair of antiparallel connected thyristors, which is governed by a very simple Zener diode based control circuit. Also, the software-based UPQC protection approach is investigated, the implementation of which does not require additional hardware

Power quality improvement in distribution system based on dynamic voltage restorer using PI tuned fuzzy logic controller

Purpose. This article proposes a new control strategy for Dynamic Voltage Restorer (DVR) in utility grid for distribution system. The proposed DVR using PI tuned fuzzy logic scheme is based on replacement of conventional DVR and voltage sag compensation in distribution system network. The novelty of the proposed work consists in presenting an enhanced PI tuned fuzzy logic algorithm to control efficiently the dynamic voltage restorer when voltage sag is suddenly occurred. Methods. The proposed algorithm which provides sophisticated and cost-effective solution for power quality problems. Our strategy is based on tuned fuzzy control of reactive powers and also closed loop for harmonic reduction in distribution system. The proposed control technique strategy is validated using MATLAB / Simulink software to analysis the working performances. Results. The results obtained clearly show that DVR using PI tuned fuzzy logic have good performances (sag compensation, harmonic reduction) compared to conventional DVR. Originality. Compensation of voltage sag/ swell in distribution for reactive power and current harmonic reduction by using DVR based PI tuned fuzzy logic controller. Practical value. The work concerns the comparative study and the application of DVR based on PI tuned fuzzy techniques to achieve a good performance control system of the distribution system. This article presents a comparative study between the conventional DVR control and PI tuned fuzzy DVR control. The strategy based on the use of a PI tuned fuzzy controller algorithm for the control of the continuous voltage sag and harmonic for the distribution network-linear as well as non-linear loads in efficient manner. The study is validated by the simulation results based on MATLAB / Simulink software.Мета. У статті пропонується нова стратегія управління пристроєм динамічного відновлення напруги (ДВН) в мережі розподільної системи. Запропонований ДВН, що використовує схему нечіткої логіки з ПІ-налаштуванням, заснований на заміні звичайного ДВН та компенсації провалів напруги в мережі розподільної системи. Новизна запропонованої роботи полягає у поданні удосконаленого алгоритму нечіткої логіки з ПІ-налаштуванням для ефективного управління динамічним відновником напруги при раптовому виникненні провалу напруги. Методи. Запропоновано алгоритм, який забезпечує складне та економічне вирішення проблем якості електроенергії. Наша стратегія заснована на нечіткому керуванні реактивною потужністю, що налаштовується, а також на замкненому контурі для зниження гармонік в розподільній системі. Запропонована методика управління перевіряється за допомогою програмного забезпечення MATLAB/Simulink для аналізу робочих характеристик. Результати. Отримані результати чітко показують, що ДВН, який використовує нечітку логіку з ПІ-налаштуванням, має хороші характеристики (компенсація провалів, зниження гармонік) порівняно із звичайним ДВН. Оригінальність. Компенсація провалів/стрибків напруги у розподільній мережі для зниження реактивної потужності та гармонік струму за допомогою нечіткої логіки з використанням ДВН на основі контролера нечіткої логіки з ПІ-налаштуванням. Практична цінність. Робота стосується порівняльного дослідження та застосування ДВН на основі нечіткої логіки з ПІ-налаштуванням для досягнення хороших параметрів системи керування розподільною системою. У статті представлено порівняльне дослідження звичайного керуванням ДВН та нечіткого керування ДВН з ПІ-налаштуванням. Стратегія, заснована на використанні алгоритму нечіткої логіки з ПІ-налаштуванням для ефективного керування безперервним провалом напруги та гармоніками для лінійних та нелінійних навантажень розподільчої мережі. Дослідження підтверджено результатами моделювання на основі програмного забезпечення MATLAB/Simulink

Unified Power Quality Conditioner for Grid Integration of Wind Generators

A Unified Power Quality Conditioner (UPQC) is relatively a new member of the custom power device family. It is a comprehensive custom power device, with integrated shunt and series active filters. The cost of the device, which is higher than other custom power/FACTS devices, because of twin inverter structure and control complexity, will have to be justified by exploring new areas of application where the cost of saving power quality events outweighs the initial cost of installation. Distributed generation (such as wind generation) is one field where the UPQC can find its potential application. There has been a considerable increase in the power generation from wind farms. This has created the necessity for wind farms connectivity with the grid during power system faults, voltage sags and frequency variations. The application of active filters/custom power devices in the field of wind generation to provide reactive power compensation, additional fault ride through capability and to maintain Power Quality (PQ) at the point of common coupling is gaining popularity. Wind generation like other forms of distributed generation often relies on power electronics technology for flexible interconnection to the power grid. The application of power electronics in wind generation has resulted in improved power quality and increased energy capture. The rapid development in power electronics, which has resulted in high kVA rating of the devices and low price per kVA, encourages the application of such devices at distribution level. This work focuses on development of a laboratory prototype of a UPQC, and investigation of its application for the flexible grid integration of fixed and variable speed wind generators through dynamic simulation studies. A DSP based fully digital controller and interfacing hardware has been developed for a 24 kVA (12 kVA-shunt compensator and 12 kVA-series compensator) laboratory prototype of UPQC. The modular control approach facilitates the operation of the device either as individual series or shunt compensator or as a UPQC. Different laboratory tests have been carried out to demonstrate the effectiveness of developed control schemes.A simulation-based analysis is carried out to investigate the suitability of application of a UPQC to achieve Irish grid code compliance of a 2 MW Fixed Speed Induction Generator (FSIG). The rating requirement of the UPQC for the wind generation application has been investigated. A general principle is proposed to choose the practical and economical rating of the UPQC for this type of application. A concept of UPQC integrated Wind Generator (UPQC-WG) has been proposed. The UPQC-WG is a doubly fed induction machine with converters integrated in the stator and rotor circuits and is capable of adjustable speed operation. The operation of UPQC-WG under sub and super-synchronous speed range has been demonstrated. The Irish grid code compliance of the same has been demonstrated with a detailed dynamic simulation