Virtual Instrument of Harmonics Detection Based on Neural Network Adaptive Filters

This study investigated the adaptive detection principle based on a single artificial neuron, and constructed a method for detecting harmonics using the artificial neural network technique. Based on the established method, and by comprehensively processing the obtained harmonics data using the LabVIEW software-developing environment of the virtual instrument, the harmonic waves were detected and analyzed. Finally, the analysis of current ball crusher harmonics verified that the designed system was effective

Merenje snage po standardu IEEE 1459-2010 upotrebom rezonatorskih filterskih struktura

Liberalizacijom tržišta električne energije merenje električne snage i energije u nesinusoidalnim uslovima dobilo je veliki značaj. Ta tema je još uvek predmet aktivnih rasprava, tako da ne postoji neka generalizovana teorija koja se može uzeti kao osnova za potrebe obračuna, evaluacije kvaliteta energije, detekcije izvora harmonika i kompenzacije u energetskim sistemima. Kao posledica, postojeći standardi se odnose na sinusoidalne slučajeve i ne daju definiciju reaktivne energije (i/ili snage) u nesinusoidalnim uslovima. Slično, oni ne daju specifične zahteve za tačnost i odgovarajuće uslove testiranja u prisustvu harmonijskih izobličenja. Jedini standard koji se odnosi na ovu problematiku je IEEE Std. 1459-2010 koji ne daje definiciju reaktivne snage u nesinusoidalnim uslovima. Koncept ovog IEEE standarda je baziran na razdvajanju snage na fundamentalni i nefundamentalni deo. Ovaj prilaz separacije na fundamentalni i harmonijski deo može se primeniti na najbitnije veličine i može se iskoristiti kao indikator kvaliteta. U radu je prikazana jedna efikasna algoritamska struktura za računanje električnih veličina definisanih standardom IEEE 1459-2010. Struktura se sastoji od dva dekuplovana dela. Za estimaciju spektra napona i struje korišćena je efikasna metoda bazirana na paralelnoj strukturi rezonantnih filtera sa zajedničkom povratnom vezom. U drugom delu strukture se na osnovu poznatog spektra naponskog i strujnog signala računaju komponente snage i indikatori kvaliteta na osnovu definicija datih u standardu IEEE 1459-2010. Predloženi algoritam je pogodan za primene u realnom vremenu. Realizacijom virtualnog instrumenta baziranog na PC računaru i programskom paketu LabVIEW, u cilju procene performansi algoritma, izvršene su računarske simulacije i eksperimentalna merenja i dati njihovi rezultati.This paper proposes an accurate and computationally efficient implementation of the IEEE Std. 1459-2010 for power measurements. An implementation is based on digital resonators embedded in a feedback loop. In the first algorithm stage, the unknown signal harmonic parameters are estimated. By this, the voltage and current signals are processed independently of each other. In the second algorithm stage, the unknown power components are estimated (calculated) based on estimated spectra. To demonstrate the performance of the developed algorithm, computer-simulated data and laboratory testing records are processed. Simple LabView implementation, based on the point-by-point processing feature, demonstrates techniques modest computation requirements and confirms that the proposed algorithm is suitable for real-time applications

Merenje komponenti električne snage po standardu IEEE 1459-2010

Merenje u nesinusoidalnim uslovima je u centru istraživanja i mnogo se napora ulaže da se pojam reaktivne snage star više od sedamdeset godina definiše na nov način. Postoji niz pristupa rešavanju problema definisanja snaga i/ili pokušaja koncipiranja merne instrumentacije za merenje snaga u sistemima naizmenične struje pod nesinusoidalnim uslovima. Jedini standard koji se odnosi na specifične zahteve za tačnost i odgovarajuće uslove testiranja u prisustvu harmonijskih izobličenja je IEEE Std. 1459-2010, koji ne daje definiciju reaktivne snage u nesinusoidalnim uslovima. Koncept ovog IEEE standarda je baziran na raz-dvajanju snage na fundamentalni i nefundamentalni deo. U literaturi su prisutne različite tehnike za imple-mentaciju standarda IEEE Std. 1459-2010. Ovaj standard je implementiran pomoću dva osnovna prilaza: (1) dvostepeni algoritam sa estimacijom harmonijskih spektara naponskog i strujnog signala u prvom koraku i računanjem nepoznatih komponenti snage u drugom koraku i (2) filterska implementacija kombinovana sa Clarke-Park transformacijom u slučaju trofaznog sistema. U radu je prikazana nova metoda za merenje električnih veličina definisanih standardom IEEE 1459-2010 koristeći drugi pristup. Ključni elementi su adaptivni pojasni i niskopropusni FIR filteri koji izdvajaju fundamentalnu i jednosmernu komponentu. U radu su korišćene tehnike oversemplinga i decimacionih filtera, čime se izbegavaju problemi vezani za osetljivost na zaokruživanje koeficijenata FIR kaskadnih filtera velikog reda, smanjuje obim numeričkih računanja i povećava tačnost merenja. Estimacija simetričnih komponenti vrši se pomoću matrice adaptivnih faznih korektora. U cilju procene performansi algoritma izvršene su računarske simulacije i dati njihovi rezultati.In this paper, the design and implementation of a novel recursive method for the power measurement ac-cording to the IEEE Standard 1459-2010 have been described. The most important parts are adaptive band and low-pass FIR filters that extract fundamental and dc components, respectively. In addition, by using oversampling techniques and decimation filters, coefficient sensitivity problems of the large-order FIR comb cascade structure are overridden and the parameter estimation accuracy is improved. The symmetrical components are estimated through a transformation matrix of adaptive phase shifters. The effectiveness of the proposed techniques is demonstrated by simulation results

Elektronski sistem za analizu polifaznih opterećenja baziran na FPGA

Electronic devices industry is characterized by a very dynamic growth. Such quick advancement is not recognized in other technological branches. It is exponential and it can be represented by Moore’s law, which describes long-term tendency: the number of active components integrated on circuit doubles every eighteen months, keeping constant production price. This trend stands almost fifty years, and it will stand in the near future. Moore’s law is closely related to electronic device’s properties: processor speed, memory capacity, resolution, etc. Exponential growth had immense impact on world economy and it led to significant changes in lifestyle. Consequently, electronic devices are cheaper and more available on the market. As a result, electronic equipment takes a bigger portion in overall power consumption. Electronic devices are complex circuits, consisting active semiconductor components that require direct current for polarisation. Electric energy is delivered to end users using three-phase alternating current distribution. Three-phase distribution is suitable for electric power transfer; however it cannot be directly applied to electronic circuits. Alternating current must be converted to direct current, using AC/DC power converters. Converter is electric circuit containing transformer, or switch mode power supply drawing power from the mains in pulses hence it is nonlinear. It can be analysed as two-port network with reactive and nonlinear impedance. Characterisation of power converter is performed by means of determining electrical quantities, power and power quality parameters – power factor and total harmonic distortion. In linear circuits, consisting of linear loads, the currents and voltages are sinusoidal and the power factor effect arises only from the difference in phase between the current and voltage. When nonlinear loads are present one should introduce new quantities in the calculations emanated by the harmonics and related power components. Now the power factor can be generalized to a total or true power factor where the apparent power, involved in its calculations, includes all harmonic components. This is of importance in characterization and design of practical power systems which contain non-linear loads such as rectifiers, and especially, switched-mode power supplies. Phase difference between current and voltage, as well as harmonic distortion has negative impact on distribution system. Therefore, industry standards regulate the limits (minimum) of power factor. One of the most paradigmatic examples is personal computer that typically includes switched-mode power supply (SMPS) with output power ranging from 150 W to 500 W. SMPS with passive power correction factor (PFC) can achieve power factor of about 0.7–0.75, SMPS with active PFC – up to 0.99, while SMPS without any PFC has power factor of about 0.5–0.65 in the best. Since the problem of distortion becomes ubiquitous, it can be either observed at the distribution system level, or one has to take local measurement of the properties of this kind of loads. Measurement of power factor and distortion, however, usually requires dedicated equipment. For example, use of a classical ammeter will return incorrect results when attempting to measure the AC current drawn by a non-linear load and then calculate the power factor. A true RMS multimeter must be used to measure the actual RMS currents and voltages and apparent power. To measure the real power or reactive power, a wattmeter designed to properly work with non-sinusoidal currents must be also used. Contemporary methods and algorithms for spectrum analysis are presented in this thesis. The basic definitions of parameters describing nonlinear loads in one-phase and three-phase circuits are introduced. Alternative definitions for reactive power and their calculation methods are elaborated. A new approach to polyphase load analysis is presented: system for nonlinear load characterization which is flexible, scalable, with advanced options. The solution introduced in the thesis brings all benefits of virtual instrumentation, keeping main advantage of classical instrument – determinism in measurement. The hardware component of the system is implemented using field programming gate array (FPGA) in control of data acquisition. The software part is implemented in two stages, executing on real-time operating system and general purpose operating system. Described realization provides possibility for calculating a large number of parameters that characterize nonlinear loads, which is impossible using classical instruments. This is of great importance particularly in calculation of alternate definitions of reactive power. The system is scalable; it can be upgraded in number of calculated parameters, as well as in number of independent measurement channels or functionality. The system is open; it can be modified to be a part of harmonic compensation circuitry or aimed for hardware-in-the-loop simulations. The system is flexible; it is implemented on different platforms for different purposes: as laboratory equipment for real time measurements (PXI controller equipped with PXI-7813R FPGA card and expansion chassis), as compact industrial device for real time operation (installed on programmable automation controller) or simple portable instrument equipped with computer interface. It consists of three subsystems: acquisition subsystem, real time application for parameter calculations and virtual instrument for additional analysis and data manipulation. Acquisition subsystem consists of acquisition modules for A/D conversion, FPGA circuit and interface for computer or programmable automation controller. A/D resolution is 24-bit, with 50 kSa/s sampling rate and dynamic range ±300 V for voltages and ±5 A for currents. Function of FPGA circuit is acquisition control and harmonic analysis. Real time application calculates power and power quality parameters deterministically and save calculated values on local storage. The application is executed on real time operating system. Virtual instrument for additional analysis and data manipulation represents user interface of described system. It runs on general purpose operating system, physically apart from rest of the system. Communication is achieved by TCP/IP. Parameters and values obtained by means of acquisition and calculations are presented numerically and graphically. The usage of the system is also described. Nonlinear single-phase (SMPS, LED, CFL) and three-phase loads are examined in order to present all possibilities of new system

Null detection using low resolution A/D converter

U tezi je rešavan centralni problem – detekcija nule dvobitnom stohastičkom digitalnom mernom metodom (SDMM). Formulisane su dve metode detekcije nule primenom dvobitne SDMM. Po prvoj metodi dinamička rezerva je oko 100 dB a po drugoj ne manje od 160 dB. Obe metode su proverene teorijski, simulaciono i eksperimentalno. Pored rešenja centralnog problema, dato je i nekoliko rešenja problema koji su sa njim vezani. Hipoteza ove teze – „dvobitna SDMM je u opsegu 0 % - 10% FS bolja od standardne sempling metode (SSM)“ – je potpuno potvrđena u svim razmatranim slučajevima.The main goal of this thesis was null-detection using a two-bit stochastic digital measurement method (SDMM). Two methods of null-detection, using two-bit SDMM, were formulated. Using the first method around 100 dB of dynamic reserve was achieved and using the second one no less than 160 dB. Both methods were theoretically, using simulation and experimentally confirmed. In addition to the solution of the main problem, several other related problems were also solved. The hypothesis of this thesis – “two-bit SDMM in range from 0 % - 10 % FS is better than the standard sampling method (SSM)” has been fully confirmed in all considered cases

Finansijski sistem i ekonomski rast

Finansijski sistem, kao integralni deo privrednog sistema, ima ključnu ulogu u povezivanju štednje i investicija. Stoga je nesporno važna uloga finansijskog sistema u funkcionisanju svake tržišne privrede. Osim mobilizacije i trnasfera štednje od finansijski suficitarnih ka finansijski deficitarnim subjektima, finansijski sistem uključuje funkcionisanje odgovarajućeg mehanizma kontrole korporativnog upravljanja, omogućava upravljanje rizicima imanentnim finansijskom poslovanju i olakšava razmenu dobara i usluga. Svaka od navedenih funkcija ima uticaj na akumulaciju kapitala i razvoj tehnoloških inovacija kao primarnih determinanti ekonomskog rasta. S druge strane, ekspanzija realnog sektora podrazumeva rast obima finansijskih transakcija. To dalje predstavlja osnovu za uvećanje obima i kvaliteta finansijskih proizvoda i usluga. Polazeći od različitih teorijskih modela i empirijskih rezultata, predmet istraživanja u doktorskoj disertaciji je međuzavisnost razvoja finansijskog sistema i ekonomskog rasta. S obzirom da su u tranzicionim privredama mehanizmi transfera finansijskih sredstava nedovoljno razvijeni, a tempo ekonomskog rasta spor, definisano područije istraživanja ima poseban teorijski i praktičan značaj. Shodno tome, osnovni cilj doktorske disertacije je da teorijsko-metodološki i empirijski sagleda vezu između razvoja finansijskog sistema i ekonomskog rasta. U doktorskoj disertaciji su najpre analizirani osnovni elementi finansijskog sistema. Predmet detaljne analize bile su funkcije finansijskog sistema koje objašnjavaju zbog čega se u svakoj privredi finansijskom sistemu pridaje izuzetna važnost. Analizirani su modeli finansijskog sistema, sa posebnim osvrtom na njihove prednosti i nedostake prilkom obavljanja osnovnih funkcija. Kao jedno od istraživačkih područja izdvajilo se pitanje determinanti i pokazatelja razvoja finasijskog sistema i ekonomskog rasta. Posebna pažnja posvećena je modelima koji dovode u vezu razvoj finansijskog sistema i ekonomski rast. Empirijskim istraživanjem na primeru Republike Srbije utvrđena je pozitivna korelacija između razvoja finansijskog posredovanja banaka i stope ekonomskog rasta. Takođe, otkrivena je jednosmerna kauzalna veza koja ide iz prvaca razvoja finansijskog posredovanja banaka ka stopi ekonomskog rasta. Otuda, smatra se opravdanim koncipiranje politika i strategija koje uključuju stimulisanje daljeg razvoja bankarskog sektora i podsticanje razvoja tržišta kapitala i nebankarskih finansijkih posrednika.The financial system, as an integral part of the economic system, plays a key role in linking savings and investment. Therefore, the role of the financial system in the functioning of every market economy is undoubtedly important. In addition to the mobilization and transfer of savings from entities with financial surplus to those with financial deficit, the financial system involves the functioning of appropriate corporate governance control mechanisms, enables risk management, imminent in financial operations, and facilitates the exchange of goods and services. Each of these functions has an impact on capital accumulation and development of technological innovation, as the primary determinants of economic growth. At the same time, the expansion of the real sector means increase in the volume of financial transactions. It stands for the basis for the increase in volume and quality of financial products and services. Starting from different theoretical models and empirical results, the research subject in the doctoral thesis is the correlation between financial system development and economic growth. Given that, in transition economies, mechanisms of funds transfer are insufficiently developed, and the pace of economic growth slow, the defined research area has special theoretical and practical significance. Consequently, the basic objective of the doctoral thesis is to, from the theoretical, methodological, and empirical aspects, examine the correlation between financial system development and economic growth. The doctoral thesis first analyzed the basic elements of the financial system. The subject of a detailed analysis referred to the functions of the financial system, which explain why each economy gives particular importance to the financial system. The analysis focused on the models of the financial system, with particular emphasis on their advantages and disadvantages in performing basic functions. The issue of determinants and indicators of financial system development and economic growth stood out as one of the research areas. Special attention was paid to models that connect financial system development and economic growth. Empirical research into the example of the Republic of Serbia established positive correlation between the development of financial intermediation by banks and economic growth rates. What is more, one-way causality from the development of financial intermediation by banks to the economic growth rate was revealed. Therefore, it is considered justifiable to design policies and strategies that include stimulating further development of the banking sector and encourage the development of capital markets and non-bank financial intermediaries

Synchrophasor Measurement Using Substation Intelligent Electronic Devices: Algorithms and Test Methodology

This dissertation studies the performance of synchrophasor measurement obtained using substation Intelligent Electronic Devices (IEDs) and proposes new algorithms and test methodology to improve and verify their performance when used in power system applications. To improve the dynamic performance when exposed to sinusoidal waveform distortions, such as modulation, frequency drift, abrupt change in magnitude, etc, an adaptive approach for accurately estimating phasors while eliminating the effect of various transient disturbances on voltages and currents is proposed. The algorithm pre-analyzes the waveform spanning the window of observation to identify and localize the discontinuities which affect the accuracy of phasor computation. A quadratic polynomial signal model is used to improve the accuracy of phasor estimates during power oscillations. Extensive experimental results demonstrate the advantages. This algorithm can also be used as reference algorithm for testing the performance of the devices extracting synchronized phasor measurements. A novel approach for estimating the phasor parameters, namely frequency, magnitude and angle in real time based on a newly constructed recursive wavelet transform is developed. This algorithm is capable of estimating the phasor parameters in a quarter cycle of an input signal. It features fast response and achieves high accuracy over a wide range of frequency deviations. The signal sampling rate and data window size can be selected to meet desirable application requirements, such as fast response, high accuracy and low computational burden. In addition, an approach for eliminating a decaying DC component, which has significant impact on estimating phasors, is proposed using recursive wavelet transform. This dissertation develops test methodology and tools for evaluating the conformance to standard-define performance for synchrophasor measurements. An interleaving technique applied on output phasors can equivalently increase the reporting rate and can precisely depict the transient behavior of a synchrophasor unit under the step input. A reference phasor estimator is developed and implemented. Various types of Phasor Measurement Units (PMUs) and PMU-enabled IEDs (Intelligent Electronic Devices) and time synchronization options have been tested against the standards using the proposed algorithm. Test results demonstrate the effectiveness and advantages