Renewable energy sources including photovoltaic cells, fuel cells, and wind turbines require converters with high voltage gain in order to interface with power transmission and distribution networks. These conversions are conventionally made using bulky, complex, and costly transformers. Multiple modules of single-switch, single-inductor DC-DC converters can serve these high-gain applications while eliminating the transformer. This work generally classifies multiple modules of single-switch, single-inductor converters as high gain DC-DC converters transformers. The gain and efficiency of both series and cascade configurations are investigated analytically, and a method is introduced to determine the maximum achievable gain at a given efficiency. Simulations are used to verify the modeling approach and predict the performance at different power levels. Experimental prototypes for both low power and high power applications demonstrate the value of multiple module converters in high gain DC-DC converters for renewable energy applications.

Conduction based compact thermal modeling of DC/DC converters, which are electronic components commonly used in military applications, are investigated. Three carefully designed numerical case studies are carried out at component, board and system levels using ICEPAK software. Experiments are conducted to gather temperature data that can be used to study compact thermal models (CTMs) with different levels of simplification. In the first (component level) problem a series of conduction based CTMs are generated and used to study the thermal behavior of a Thin-Shrink Small Outline Package (TSSOP) type DC/DC converter under free convection conditions. In the second (board level) case study, CTM alternatives are produced and investigated for module type DC/DC converter components using a printed circuit board (PCB) of an electro-optic system. In the last case study, performance of the CTM alternatives generated for the first case are assessed at the system level using them on a PCB placed inside a realistic avionic box. v Detailed comparison of accuracy of simulations obtained using CTMs with various levels of simplification is made based on experimentally obtained temperature data. Effects of grid size and quality, choice of turbulence modeling and space discretization schemes on numerical solutions are discussed in detail. It is seen that simulations provide results that are in agreement with measurements when appropriate CTMs are used. It is also showed that remarkable reductions in modeling and simulation times can be achieved by the use of CTMs, especially in system level analysis.

Due to the continuous power supply reduction, Charge Pumps, also referred to as DC-DC converters, circuits are widely used in integrated circuits (ICs) to generate high voltages for many applications, such as EEP-ROMs, Flash memories for programming and erasing of the floating gate, switched capacitor circuits, operational amplifiers, voltage regulators, LCD drivers, piezoelectricactuators, etc. A charge pump is a kind of DC to DC converter that uses capacitors as energy storage elements to create either a higher or lower voltage power source. The development of the charge pumps is motivated by ever increasing the needs for the small form factor (i.e small size and low weight), high-conversion-efficiency and low costpower management system, which is the best candidate suitable to meet the needs of continuosly shrinking portable electronic devices like MP3 players, cellular phones, PDA's. / text

Increasing power density of switch mode power supplies, by increasing their switching frequency has becoming a challenging obstacle for EMI mitigation. The passive EMI suppression technique has always been the primary solution to fulfill the EMC requirement in terms of conducted emission limits. However, the call for stringent power supplies specifications renders the passive techniques less desirable, due to their increasing size and power losses. In other words, the greater the power density of the converter, the bigger the passive filter. Other suppression techniques such as the spread spectrum frequency modulation (SSFM), and soft switching, prove to have less performance and much complex to implement. The active analog EMI filters provide the basic noise suppression technique; however, their performance is dramatically impeded at higher frequency. This solution requires an additional small size passive filter to complete the EMC spectrum for conducted emissions. Digital active filtering techniques offer advantages of flexibility, fewer external components and reduced overall size and power losses as compared to conventional passive filtering techniques. In this thesis DSP-based and FPGA-based EMI control techniques to mitigate the conducted emissions of switch mode power converters are proposed. These techniques are implemented in-lieu of the passive filtering techniques, by keeping equal or better performance. Moreover, these solutions can be configured as a stand-alone or integrated into the converter digital controller algorithm. Finally, the proposed solutions are implemented into three types of power converters, namely, a AC-DC power factor corrected converter, DC-AC micro-inverter for Photovoltaic application, and DC-DC for Electric Vehicle (EV) battery charger. Analytical, simulation and experimental results are provided to verify the proposed solutions. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2011-11-07 10:48:49.191

Multifrequency averaging is one of the widely used modeling and simulation techniques today for the analysis and design of power electronic systems. This technique is capable of providing the average behavior as well as the ripple behavior of power electronic systems. Hysteresis current control has fast response and internal current stability through controlling switches to maintain the current within a given hysteresis band of a given current command. However the state space variables in a hysteresis controlled system cannot be directly approached by multifrequency averaging method because of time varing switching frequency. In this thesis, a method of applying multifrequency averaging to hysteresis current controlled dc-dc converters is proposed. A dc-dc converter model with the application of this method has been successfully developed and validated both in simulation and experiment.

Στις μέρες μας, οι ολοένα αυξανόμενες ενεργειακές ανάγκες καθώς και οι η μόλυνση του περιβάλλοντος είναι οι κύριοι λόγοι που η χρήση των ανανεώσιμων πηγών ενέργειας στα σύγχρονα συστήματα ενέργειας έχει αυξηθεί τις τελευταίες δεκαετίες. Τα φωτοβολταϊκά συστήματα είναι μια από τις πιο συνήθεις και αποτελεσματικές ανανεώσιμων πηγών για συνδεδεμένα στο δίκτυο ή αυτόνομα συστήματα. Ο σκοπός της παρούσας εργασίας είναι η μελέτη και προσομοίωση έλεγχου σε μετατροπέα δυο βαθμίδων για σύνδεση φωτοβολταικού συστήματος. Αρχικά, θα μελετήσουμε θεωρητικά διάφορους τύπους τοπολογιών που περιλαμβάνουν αντιστροφέα, στην περίπτωση μας, θα μοντελοποιήσουμε και προσομοιώσουμε ένα DC-DC μετατροπέα σε σύνδεση αλυσίδας με έναν τριφασικό DC-AC αντιστροφέα σε ένα απομονωμένο σύστημα. Ειδικότερα θα παρουσιάσουμε θεωρητικά και πειραματικά αποτελέσματα έλεγχου της τάσης εξόδου του μετατροπέα. Το βασικό κομμάτι αυτής της εργασίας είναι τα αποτέλεσμα του ελεγκτή που είναι βασισμένος στην παθητικότητα διασύνδεσης και εκχώρηση απόσβεσης (IDA PBC). Τέλος, θα μοντελοποιήσουμε και προσομοιώσουμε τον DC-AC μετατροπέα, του οποίου ελέγχουμε την τάση εξόδου από τους γνωστούς μας σε όλους αναλογικούς-ολοκληρωτικούς (PI) ελεγκτές. / Nowadays, increased energy needs and the increasing pollution levels of the environment are the main reasons that usage of renewable energy sources to modern power systems has significantly increased in the last decades. Photovoltaic (PV) generator systems are one of the most common and efficient renewable energy applications for grid-connected or stand-alone systems. The aim of the present thesis is the study and the simulation of control of a two level power converter used in photovoltaic systems. Firstly, we will study theoretically different types of topologies that include inverters, in our case, we model and simulate a DC-DC boost power converter string connected with a three phase DC-AC inverter to a stand-alone system. Especially we will present theoretical and experimental results controlling the DC-DC converter output voltage. The basic part of this thesis are the results of the controller, which is designed following the passivity-based interconnection and damping assignment methodology (IDA PBC). Finally, we will model and simulate the DC-AC inverter, where its output voltage is controlled by the well-known, proportional-integral (PI) controllers.

Les évènements climatiques de ces dernières années ont encouragé de nombreux pays à augmenter la part des énergies renouvelables et non génératrices de gaz à effets de serre. Cependant, pour faciliter leur intégration à grande échelle, le besoin d’un super réseau européen se fait sentir. Ce nouveau réseau, principalement basé sur du courant continu sous haute tension (HVDC) nécessitera l’utilisation de convertisseurs DC-DC. Par conséquent, ce mémoire propose et étudie des topologies basées sur l’association de convertisseurs DC-DC élémentaires isolés. Il est organisé en une introduction, 3 chapitres et une conclusion. Dans l’introduction, un état de l’art est réalisé sur les technologies actuellement mises en oeuvre dans les applications HVDC. Le contexte de l’étude, lié au développement des réseaux DC interconnectés et maillés est ensuite développé. Dans le premier chapitre, des solutions basées sur l’association de convertisseurs DC DC élémentaires isolés sont étudiées puis comparées en termes de dimensionnement des éléments réactifs et de rendement. Cette étude nous a permis de sélectionner trois topologies pour la suite de notre travail. Dans le deuxième chapitre, nous évoquons tout d’abord les différentes problématiques pouvant apparaitre lors de la mise en oeuvre des solutions proposées. Dans un second temps, en prenant une ferme éolienne offshore comme cas d’application, les solutions proposées sont comparées en termes de pertes et de nombre de composants avec une topologie basée sur une association de convertisseurs modulaires multiniveaux (MMC) utilisés dans les réseaux HVDC. Le troisième chapitre présente l’étude et la mise en oeuvre de deux prototypes de convertisseur DC-DC isolés, d’une puissance de 100 kW et fonctionnant sous une tension de 1,2 kV. Ces prototypes ont permis de valider expérimentalement les performances des topologies étudiées dans le premier chapitre. Finalement, la dernière partie propose une conclusion des travaux présentés dans cette thèse. Ces travaux nous ont permis de montrer que les solutions proposées présentent un intérêt pour le cas d’application sélectionné. / The catastrophic environmental effects seen in the last couple of decades have encouraged many countries to increase the proportion of C02-free energy from renewable sources. However, for the easier integration of these energies on a large scale, the need of a European SuperGrid has emerged. This new grid, mainly based on High-Voltage- Direct-Current (HVDC) will require the use of DC-DC converters. Therefore, this manuscript proposes and studies topologies based on the association of isolated elementary DC-DC converters. It is organized in one introduction, 3 chapters and one conclusion. In the introduction, a state-of-the-art of the technologies currently used in HVDC applications is proposed. The context of the study, linked to development of the meshed DC grids, is developed afterwards. In the first chapter, solutions based on the association of elementary isolated DC-DC converters are studied and then compared in terms of reactive components sizing and efficiency. This study permitted the selection of three topologies for the rest of our work. In the second chapter, we mention the issues which may appear during the implementation of the solution. Then, by taking an offshore wind farm as application case, the solution is compared, in terms of loss and component number, with a topology based on the association of Modular Multilevel Converters (MMC) currently used in HVDC grids. The third chapter presents the study and the implementation of two 100 kW DC-DC converter prototypes, operating at 1.2 kV. These prototypes allowed the experimental validation of the performances of the topologies studied in the first chapter. Finally, the last part proposes a conclusion of the work achieved in this thesis. This work allowed it to be shown that the proposed solutions are interesting for the selected application case.

abstract: This thesis investigates different unidirectional topologies for the on-board charger in an electric vehicle and proposes soft-switching solutions in both the AC/DC and DC/DC stage of the converter with a power rating of 3.3 kW. With an overview on different charger topologies and their applicability with respect to the target specification a soft-switching technique to reduce the switching losses of a single phase boost-type PFC is proposed. This work is followed by a modification to the popular soft-switching topology, the dual active bridge (DAB) converter for application requiring unidirectional power flow. The topology named as the semi-dual active bridge (S-DAB) is obtained by replacing the fully active (four switches) bridge on the load side of a DAB by a semi-active (two switches and two diodes) bridge. The operating principles, waveforms in different intervals and expression for power transfer, which differ significantly from the basic DAB topology, are presented in detail. The zero-voltage switching (ZVS) characteristics and requirements are analyzed in detail and compared to those of DAB. A small-signal model of the new configuration is also derived. The analysis and performance of S-DAB are validated through extensive simulation and experimental results from a hardware prototype. Secondly, a low-loss auxiliary circuit for a power factor correction (PFC) circuit to achieve zero voltage transition is also proposed to improve the efficiency and operating frequency of the converter. The high dynamic energy generated in the switching node during turn-on is diverted by providing a parallel path through an auxiliary inductor and a transistor placed across the main inductor. The paper discusses the operating principles, design, and merits of the proposed scheme with hardware validation on a 3.3 kW/ 500 kHz PFC prototype. Modifications to the proposed zero voltage transition (ZVT) circuit is also investigated by implementing two topological variations. Firstly, an integrated magnetic structure is built combining the main inductor and auxiliary inductor in a single core reducing the total footprint of the circuit board. This improvement also reduces the size of the auxiliary capacitor required in the ZVT operation. The second modification redirects the ZVT energy from the input end to the DC link through additional half-bridge circuit and inductor. The half-bridge operating at constant 50% duty cycle simulates a switching leg of the following DC/DC stage of the converter. A hardware prototype of the above-mentioned PFC and DC/DC stage was developed and the operating principles were verified using the same. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

abstract: Power management circuits are employed in most electronic integrated systems, including applications for automotive, IoT, and smart wearables. Oftentimes, these power management circuits become a single point of system failure, and since they are present in most modern electronic devices, they become a target for hardware security attacks. Digital circuits are typically more prone to security attacks compared to analog circuits, but malfunctions in digital circuitry can affect the analog performance/parameters of power management circuits. This research studies the effect that these hacks will have on the analog performance of power circuits, specifically linear and switching power regulators/converters. Apart from security attacks, these circuits suffer from performance degradations due to temperature, aging, and load stress. Power management circuits usually consist of regulators or converters that regulate the load’s voltage supply by employing a feedback loop, and the stability of the feedback loop is a critical parameter in the system design. Oftentimes, the passive components employed in these circuits shift in value over varying conditions and may cause instability within the power converter. Therefore, variations in the passive components, as well as malicious hardware security attacks, can degrade regulator performance and affect the system’s stability. The traditional ways of detecting phase margin, which indicates system stability, employ techniques that require the converter to be in open loop, and hence can’t be used while the system is deployed in-the-field under normal operation. Aging of components and security attacks may occur after the power management systems have completed post-production test and have been deployed, and they may not cause catastrophic failure of the system, hence making them difficult to detect. These two issues of component variations and security attacks can be detected during normal operation over the product lifetime, if the frequency response of the power converter can be monitored in-situ and in-field. This work presents a method to monitor the phase margin (stability) of a power converter without affecting its normal mode of operation by injecting a white noise/ pseudo random binary sequence (PRBS). Furthermore, this work investigates the analog performance parameters, including phase margin, that are affected by various digital hacks on the control circuitry associated with power converters. A case study of potential hardware attacks is completed for a linear low-dropout regulator (LDO). / Dissertation/Thesis / Masters Thesis Electrical Engineering 2019

For many decades, engineers and students have heavily depended on simulation packages such as Pspice to run transit and steady-state simulation for their circuits. The majority of these circuits, such as soft switching cells, contain complicated modes of operations that require the Pspice simulation to run for a long time and, finally, it may not reach a convergent solution for these kinds of circuits. Also, there is a need for an educational tool that provides students with a better understanding of circuit modes of operation through state-plan figures and steady-state switching waveforms. The unified steady-state computer aided model proposes a simulation block that covers common unified soft-switching cells operations and can be used in topologies simulation. The simulation block has a simple interface that enables the user to choose the switching cell type and connects the developed simulation model in the desired topology configuration. In addition to the measured information that can be obtained from the circuitry around the unified simulation model, the simulation block includes some additional nodes (other than the inputs and outputs) that make internal switching cell information, such as switching voltages and currents, easy to access and debug. The model is based on mathematical equations, resulting in faster simulation times, smaller file size and greatly minimized simulation convergence problems. The Unified Model is based on the generalized analysis: Chapter 1 discusses the generalized equation concept along with a detailed generalization example of one switching cell, which is the zero current switching quasi-resonant converter ZCS-QRC. Chapter 2 presents a detailed discussion of the unified model concept, the unified model flow chart and the unified model implementation in Pspice. Chapter 3 presents the unified model applications; generating the switching cell inductor current and the switching cell capacitor voltage steady-state waveforms, the State-Plane Diagram , the feedback design using the unified model, and the chapter concludes with how the model can be used with different topologies. Finally, chapter 4 presents the summary and the future work