Distributed energy resources (DE) with power electronics interfaces and logic control using local measurements are capable of providing reactive power related to ancillary system services. In particular, local voltage regulation has drawn much attention in regards to power system reliability and voltage stability, especially from past major cascading outages. This dissertation addresses the challenges of controlling the DEs to regulate the local voltage in distribution systems. First, an adaptive voltage control method has been proposed to dynamically modify the control parameters of a single DE to respond to system changes such that the ideal response can be achieved. Theoretical analysis shows that a corresponding formulation of the dynamic control parameters exists; hence, the adaptive control method is theoretically solid. Also, the field experiment test results at the Distributed Energy Communications and Controls (DECC) Laboratory in single DE regulation case confirm the effectiveness of this method. Then, control methods have been discussed in the case of multiple DEs regulating voltages considering the availability of communications among all the DEs. When communications are readily available, a method is proposed to directly calculate the needed adaptive change of the DE control parameters in order to achieve the ideal response. When there is no communication available, an approach to adaptively and incrementally adjust the control parameters based on the local voltage changes is proposed. Since the impact from other DEs is implicitly considered in this approach, multiple DEs can collectively regulate voltages closely following the ideal response curve. Simulation results show that each method, with or without communications, can satisfy the fast response requirement for operational use without causing oscillation, inefficiency or system equipment interference, although the case with communication can perform even faster and more accurate. Since the proposed adaptive voltage regulation method in the case of multiple DEs without communication, has a high tolerance to real-time data shortage and can still provide good enough performance, it is more suitable for broad utility applications. The approach of multiple DEs with communication can be considered as a high-end solution, which gives faster and more precise results at a higher cost

Based on sliding-mode control theory, this thesis proposes an integrated design of robust speed controller and quantized current regulator to achieve the control of inverter for BLDC motor. Moreover, using Digital Signal Processor (DSP) as well as the proposed inverter technology as the control kernel, a fully digital drive module of Brushless DC motor (BLDC) is robustly designed to achieve the high-performance speed control. Under the influence of system disturbances, the designed drive module can obtain a good tracking response for speed and current control. According to the simulation and experimental studies, the proposed hybrid control strategy can simultaneously achieve the objective for the speed and current control of BLDC motor. Compared with traditional pulse-width modulation (PWM) based PID control, the better speed control performance can be conducted by the provided approach.

Recent advances in power electronics have lead to the wide spread adoption of advanced power supplies and energy efficient devices. This has lead to increased levels of harmonic currents in power systems, degrading the performance of electrical machinery and interfering with telecommunication services. Active filters provide a solution to these problems by compensating for the distorted currents drawn by non-linear loads. Optimal methods for controlling these active filters have been determined by computer simulation and experimental implementation. Methods used for isolating the harmonic content of an unbalanced three phase load current were compared by computer simulations. A technique based on the Fast Fourier Transform (FFT) was developed as part of this work and shown to perform favourably. Notch Filtering, Sinusoidal Subtraction, Instantaneous Reactive Power Theory, Synchronous Reference Frame and Fast Fourier Transform methods were simulated. The methods shown to be suitable for compensation of three phase unbalanced loads were implemented in a Digital Signal Processor to evaluate true performance. These methods were Notch Filtering, Sinusoidal Subtraction, Fast Fourier Transform, and a High Pass Filter based method. A completely digital hysteresis current controller for a three phase active filter inverter has been developed and implemented with a Field Programmable Gate Array. This controller interfaces directly to a digital signal processor and is resistant to electromagnetic interference. Results from the experimental hardware verified that the active filter model used for simulation is accurate, and may be used for further development of harmonic isolation methods. A technique using notch filtering gives the best performance for steady loads, with the FFT based technique giving the most flexible operation for a range of load current characteristics. Novel use of the FFT based harmonic isolation technique allows selective cancellation of individual harmonics, with particular application to multiple shunt filters connected in parallel.

With worldwide growing demand for electric energy, there has been a great interest in exploring photovoltaic (PV) sources. For the PV generation system, the power converter is the most essential part for the efficiency and function performance. In recent years, there have been quite a few new transformerless PV inverters topologies, which eliminate the traditional line frequency transformers to achieve lower cost and higher efficiency, and maintain lower leakage current as well. With an overview of the state-of-the-art transformerless PV inverters, a new inverter technology is summarized in the Chapter 2, which is named V-NPC inverter technology. Based this V-NPC technology, a family of high efficiency transformerless inverters are proposed and detailly analyzed. The experimental results demonstrate the validity of V-NPC technology and high performance of the transformerless inverters. For the lower power level transformerless inverters, most of the innovative topologies try to use super junction metal oxide semiconductor field effect transistor(MOSFET) to boost efficiency, but these MOSFET based inverter topologies suffer from one or more of these drawbacks: MOSFET failure risk from body diode reverse recovery, increased conduction losses due to more devices, or low magnetics utilization. By splitting the conventional MOSFET based phase leg with an optimized inductor, Chapter 3 proposes a novel MOSFET based phase leg configuration to minimize these drawbacks. Based on the proposed phase leg configuration, a high efficiency single-phase MOSFET transformerless inverter is presented for the PV micro-inverter applications. The PWM modulation and circuit operation principle are then described. The common mode and differential mode voltage model is then presented and analyzed for circuit design. Experimental results of a 250 W hardware prototype are shown to demonstrate the merits of the proposed MOSFET based phase-le and the proposed transformerless inverter. New codes require PV inverters to provide system regulation and service to improve the distribution system stabilization. One obvious impact on PV inverters is that they now need to have reactive power generation capability. The Chapter 4 improves the MOFET based transformerless inverter in the Chapter 3 and proposed a novel pulse width modulation (PWM) method for reactive power generation. The ground loop voltage of this inverter under the proposed PWM method is also derived with common mode and differential mode circuit analyses, which indicate that high-frequency voltage component can be minimized with symmetrical design of inductors. A 250-W inverter hardware prototype has been designed and fabricated. Steady state and transient operating conditions are tested to demonstrate the validity of improved inverter and proposed PWM method for reactive power generation, high efficiency of the inverter circuit, and the high-frequency-free ground loop voltage. Besides the high efficiency inverter circuit, the grid connection function is also the essential part of the PV system. The Chapter 5 present the overall function blocks for a grid-connected PV inverter system. The current control and voltage control loop is then analyzed, modeled, and designed. The dynamic reactive power generation is also realized in the control system. The new PLL method for the grid frequency/voltage disturbance is also realized and demonstrate the validity of the detection and protection capability for the voltage/frequency disturbance. At last, a brief conclusion is given in the Chapter 6 about each work. After that, future works on device packaging, system integration, innovation on inverter circuit, and standard compliance are discussed. / Ph. D.

<p>Предложен контролни алгоритам за инвертор повезан на мрежу<br />омогућава реализацију сваког профила контролисаних електричних<br />величина који је у домену физичких могућности дистрибуираног извора.<br />Другим речима, управљачки програм не обезбеђује остваривање<br />дискретног спектра режима, као што је то до сада био случај са<br />решењима предложеним у научној литератури, већ омогућава сигурну<br />производњу произвољног профила фазних струја и напона. Показано је<br />да предложено решење задовољава најстроже релевантне законске<br />регулативе. У раду је анализиран већи број функционалности и испитан<br />је њихов утицај на процес производње електричне енергије с акцентом на<br />хаваријске режиме. Разматрана је интеракција дистрибуираних изво-ра и<br />дистрибутивне мреже у режимима са поремећајима и приложен је већи<br />број експерименталних резултата прикупљених употребом HIL окружења.</p> / <p>Predložen kontrolni algoritam za invertor povezan na mrežu<br />omogućava realizaciju svakog profila kontrolisanih električnih<br />veličina koji je u domenu fizičkih mogućnosti distribuiranog izvora.<br />Drugim rečima, upravljački program ne obezbeđuje ostvarivanje<br />diskretnog spektra režima, kao što je to do sada bio slučaj sa<br />rešenjima predloženim u naučnoj literaturi, već omogućava sigurnu<br />proizvodnju proizvoljnog profila faznih struja i napona. Pokazano je<br />da predloženo rešenje zadovoljava najstrože relevantne zakonske<br />regulative. U radu je analiziran veći broj funkcionalnosti i ispitan<br />je njihov uticaj na proces proizvodnje električne energije s akcentom na<br />havarijske režime. Razmatrana je interakcija distribuiranih izvo-ra i<br />distributivne mreže u režimima sa poremećajima i priložen je veći<br />broj eksperimentalnih rezultata prikupljenih upotrebom HIL okruženja.</p> / <p>Proposed grid-connected inverter control algorithm enables production of any<br />controlled variables&rsquo; profile that is in the domain of converter&rsquo;s physical<br />capabilities. In other words, the control program does not allow only for a<br />narrow spectrum of different working regimes to be realized, as it was the case<br />previously with the solutions proposed in the literature, but can result in a safe<br />production of arbitrary meaningful phase currents and voltages profiles. It was<br />demonstrated that the proposed solution satisfies the most stringent of the Grid<br />Codes. Furthermore, advanced functionalities not addressed in the Grid Codes<br />were also analysed and the influence of those functionalities&rsquo; application on<br />the process of the energy production during the grid faults was evaluated in<br />the dissertation. Interaction between the distributed generation units and the<br />distribution network was studied and a number of HIL experimental results are<br />provided.</p>

Με το πέρασμα των χρόνων, τα συστήματα των ανανεώσιμων πηγών ενέργειας αποκτούν ολοένα και περισσότερο μέρος στα ηλεκτρικά δίκτυα. Το ενεργειακό πρόβλημα καθώς και οι επιπτώσεις στο περιβάλλον που αυτό δημιουργεί, οδηγούν σε εναλλακτικές μεθόδους παραγωγής ηλεκτρικής ενέργειας. Αυτό σημαίνει ότι προστίθονται στο δίκτυο εξαρτήματα τα οποία πρέπει να λειτουργούν αρμονικά το ένα σε σχέση με το άλλο για τον κατάλληλο χειρισμό της ηλεκτρικής ισχύος. Τέτοια εξαρτήματα είναι η μονάδα μετατροπής ενέργειας, ο μετατροπέας, το φίλτρο στην έξοδο του μετατροπέα καθώς και άλλες μονάδες πολύπλοκες ή πιο απλές. Η διακοπτική λειτουργία του μετατροπέα καθώς και η στοχαστική διαδικασία της παραγωγής ηλεκτρικής ενέργειας από τις ανανεώσιμες πηγές, προκαλούν τάσεις και ρεύματα με ανώτερες αρμονικές. Στην παρούσα διπλωματική εργασία θα εξετάσουμε διάφορες μεδόδους ελέγχου ισχύος στην πλευρά του δικτύου, με διάφορους τύπους φίλτρων και φορτίων στην έξοδο του μετατροπέα με σκοπό να εντοπίσουμε τις ομοιότητες και τις διαφορές ανάλογα με την τοπολογία που χρησιμοποιούμε. Τα συστήματα που θα εξομοιώσουμε περιλαμβάνουν την dc διασύνδεση, έναν μετατροπέα ισχύος που λειτουργεί με την μέθοδο PWM, διάφορες τοπολογίες φίλτρων όπως RL, LC και LCL σε ισχυρό δίκτυο και τέλος με διάφορα είδη φορτίων, δηλαδή σε ασθενές δίκτυο. Οι έλεγχοι θα εφαρμοστούν στο dq σύγχρονα στρεφόμενο σύστημα αναφοράς με την συχνότητα του δικτύου, με την βοήθεια του μετασχηματισμού Park έτσι ώστε να ελέγξουμε την dc τάση διασύνδεσης και να επιτύχουμε μοναδιαίο συντελεστή ισχύος από την πλευρά του δικτύου. Τέλος θα προσομοιώσουμε τα παραπάνω συστήματα στο Simulink του Matlab και θα εξάγουμε τα αντίστοιχα συμπεράσματα από τα αποτελέσματα των προσομοιώσεων. / During the years, systems of renewable energy sources are becoming more a significant part of electrical networks. The energy problem and its impact on the environment, lead to alternative methods of electricity production. This means that components added to the network must operate harmoniously in relation one to another for proper handling of electrical power. Such components are the power conversion unit, the inverter, the filter at the output of converter units and other complex or simple devices. The switching operation of the converter and the stochastic process of producing electricity from renewable sources, can provoke voltages and currents of higher harmonic spectrum. In this paper we will examine various methods to control power injected in the utility network with different types of filters and loads on the output of the converter in order to identify similarities and differences depending on the topology used. The systems will include simulation of dc link, a power converter that operates method PWM, different filter topologies such as RL, LC and LCL and then of different load topologies. The control will be applied in modern dq rotating reference system to the grid frequency, making use of the Park transformation to control the dc link voltage and succeed unit power factor in the grid side. In conclusion, simulations of these systems will be done in Simulink of Matlab and conclusions will be drowned.

This thesis deals with analysis of electric drive parts from hybrid electric vehicle, namely interior permanent magnet synchronous motor and inverter with control. First part describes a basic theory. Further, motor and inverter computer models are shown, specified simulations are performed on this models. Results are compared with values measured on real machines from accessible literary sources.

Övertoner orsakade av varvtalsstyrda motordrifter ger problem i industrisystem. Syftet med studien är att identifiera problemen och ge rekommendationer för att undvika dem. Studien utfördes som examensjobb på KTH för konsultföretaget Ramböll. En litteraturstudie i ämnet kombinerades med elkvalitémätningar på drifter hos Sandvik Mining. Elkvalitéproblem orsakade av varvtalsstyrda motordrifter kommer till stor del av att frekvensstyrningen ger olinjärt strömuttag som, om nätet inte är tillräckligt starkt, påverkar spänningskvalitén. Problemen kan vara driftstopp, störd utrustning och ökat slitage på utrustning för att nämna några. Denna studie visar att vid ändringar i system innehållande övertoner kan framtida övertonshalter approximeras för vissa fall. För att upprätta en modell över systemet där lasten ses som en övertonsgenerator utförs mätningar före ändringen. Med vissa antaganden om nätimpedansen kan sedan beräkningar av övertonshalten i systemet efter ändring utföras. I denna studie har en förenklad modell använts för att förutse övertonshalter efter ändringar. Syftet är att visa på ett resurseffektivt sätt att approximera så att information för att förebygga problem finns vid beslutsfattande om ändringar. Elkvalitéproblem skulle kunna förebyggas i högre grad och att inte göra det är onödigt slöseri med ekonomiska, ekologiska och sociala resurser. / Harmonics caused by variable speed drives create problems in industrial systems. The purpose of this study is to identify these problems and give recommendations to avoid them. The study was conducted as a bachelor thesis at the Royal Technical University in Stockholm, Sweden for the consultant company Ramboll Energy. A literature review was combined with electrical power quality measurements on variable speed motor operations conducted at Sandvik Mining in Sandviken, Sweden. Electrical quality problems caused by variable speed drives origin mainly from frequency inverter control that gives a non-linear current usage which, if the grid is not strong enough, affects voltage quality. Examples of problems are production downtime, disruption and malfunction of equipment and increased wear of equipment. This study shows that when making changes in systems containing harmonics, future harmonic levels can be approximated in some cases. Measurements before the change provide input data to model the system, describing the load as a harmonic current generator. With some assumptions on the grid impedance, calculating an approximation on harmonic after the change is possible. This study has used a simplified model for the prediction of harmonic levels after a change in the system. The purpose is to propose a cost effective way to approximate so that information on how to prevent problems …in the decision making. Electrical power quality problems could be prevented more often and not doing that is a waste of economical, environmental and social resources.

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