An Investigation of Series and Parallel Configurations for Hybrid Power Amplifiers

Power Hardware-in-the-Loop (PHIL) is becoming increasingly popular for compartmentalized testing of electric power equipment in several areas such as in electric drive systems and distributed power generation systems. The fundamental idea of PHIL is to create flexible conditions for Devices under Test (DUT) to be properly assessed in real time and dynamic conditions with their rated power levels. Connected to the DUT is the Power Amplifier (PA), which is responsible for increasing the voltage and current levels, given from the Real-Time Simulator (RTS). The DUT is a physical equipment and high-complexity models are used to control the PAs to emulate necessary conditions for the DUT to be evaluated. One of the main benefits of PHIL is that it can provide a platform for conducting a number of severe tests without risking damaging the equipment that is being emulated, while testing the actual response of the DUT. It can also help with the preliminary design and performance assessment of new types of machines, drivers and controllers, thus significantly reducing the time to market of new equipment. The flexibility of PHIL is also one of its main assets, since the combination of the RTS and the PA can be used for various applications only by changing the model and/or parameters of the emulated element. This thesis will evaluate the main architectures, control strategies and PHIL applications of PAs. Linear Power Amplifiers (LPA) provide an overall great performance due to its high bandwidth but are expensive, mostly at increased power ratings. For high PAs with fast dynamic response and reduced waveform distortion, the Hybrid Power Amplifier (HPA) configuration provides a good cost-performance compromise. HPAs are built essentially with the association of a low-cost Switch Mode Power Amplifier (SMPA) and an LPA. The first configuration to be investigated is the series connected HPA intended for high voltage systems. The SMPA consists of a Cascaded H-Bridge Multilevel (CHBM) converter for increased modularity. A single-pulse per H-bridge modulation technique called Nearest Level of Control (NLC) is used for minimizing the switching losses. However, this leads to unbalanced power consumption by the H-bridges when the SMPA provides relatively low output voltages, thus compromising the reliability and power quality of the SMPA. A new modulation technique called Split-Voltage Fist-In First-Out (SV-FIFO) that mitigates this issue is proposed. Its implementation requires the use of a supplemental, but simple, control loop based on the magnitude and frequency of the reference output voltage. Experimental results are presented to validate the design approach and demonstrate the high performance achieved with SV-FIFO. The parallel connected HPA is also evaluated in this thesis. In a similar way to the series connected HPA, the LPA provides high bandwidth (BW) and active power filtering while the bulk of the power is provided by the SMPA. The SMPA is realized with a three-phase Voltage Source Converter (VSC) and three single-phase LPAs. The contribution relies on proposing a new topology and current control strategy that aims to reduce the size of the required LPA, which is costly. This is achieved by using the reference current of the HPA for the current control loop of the LPA, and the actual HPA current as the reference for the SMPA current loop. By making the bandwidth of the current loop of the LPA higher than that the SMPA one, the first provides the fast transient components and harmonic filtering while the second, the bulk of the HPA current. Additionally, this thesis also covers the evaluation of techniques for Amplitude, Phase Angle and Frequency (APAF) detection for single-phase systems. Amplitude, phase and frequency detection is a key feature for the control of the series HPA, but it is also useful for other important applications, such as the synchronization of renewable sources to Alternate Current (AC) grids, which is a largely growing practice. APAF for single-phase systems are more challenging since they require additional and more complex techniques to determine the phase angle. Usually, both single and three-phase systems are designed for a single and known frequency, usually the grid’s frequency. However, a wider range of frequencies is necessary for other applications such as HPAs. This thesis will examine two proposed techniques for APAF. The first is based on the combination of the integral and derivative actions and the second is based on the modification of a zero-crossing detection system. Both systems are discussed in detail and validated experimentally

New Three Phase Photovoltaic Energy Harvesting System for Generation of Balanced Voltages in Presence of Partial Shading, Module Mismatch, and Unequal Maximum Power Points

The worldwide energy demand is growing quickly, with an anticipated growth rate of 48% from 2012 to 2040. Consequently, investments in all forms of renewable energy generation systems have been growing rapidly due to growth rate and climate concerns. Increased use of clean renewable energy resources such as hydropower, wind, solar, geothermal, and biomass is expected to noticeably alleviate many present environmental concerns associated with fossil fuel-based energy generation. In recent years, wind and solar energies have gained the most attention among all other renewable resources. As a result, both have become the target of extensive research and development for dynamic performance optimization, cost reduction, and power reliability assurance. The performance of Photovoltaic (PV) systems is highly affected by environmental and ambient conditions such as irradiance fluctuations and temperature swings. Furthermore, the initial capital cost for establishing the PV infrastructure is very high. Therefore, it is essential that the PV systems always harvest the maximum energy possible by operating at the most efficient operating point, i.e. Maximum Power Point (MPP), to increase conversion efficiency to reach 100% and thus result in lowest cost of captured energy. The dissertation is an effort to develop a new PV conversion system for large scale PV grid-connected systems which provides 99.8% efficacy enhancements compared to conventional systems by balancing voltage mismatches between the PV modules. Hence, it analyzes the theoretical models for three selected DC/DC converters. To accomplish this goal, this work first introduces a new adaptive maximum PV energy extraction technique for PV grid-tied systems. Then, it supplements the proposed technique with a global search approach to distinguish absolute maximum power peaks within multi-local peaks in case of partially shaded PV module conditions. Next, it proposes an adaptive MPP tracking (MPPT) strategy based on the concept of model predictive control (MPC) in conjunction with a new current sensor-less approach to reduce the number of required sensors in the system. Finally, this work proposes a power balancing technique for injection of balanced three-phase power into the grid using a Cascaded H-Bridge (CHB) converter topology which brings together the entire system and results in the final proposed PV power system. The developed grid connected PV solar system is evaluated using simulations under realistic dynamic ambient conditions, partial shading, and fully shading conditions and the obtained results confirm its effectiveness and merits comparted to conventional systems. The resulting PV system offers enhanced reliability by guaranteeing effective system operation under unbalanced phase voltages caused by severe partial shading

Design and control of a multicell interleaved converter for a hybrid photovoltaic-wind generation system

The solution for the generating energy derived from non-polluting sources configures a worldwide problem, which is undetermined, complex, and gradual; and certainly, passes through the diversification of the energetic matrix. Diversification means not only having different sources converted into useful energy, like the electricity, but also decentralizing the energy generation in order to fit with higher adequacy the demand, which is decentralized too. Distributed Generation proposes this sort of development but in order to increase its penetration several technical barriers must be overpassed. One of them is related to the conversion systems, which must be more flexible, modular, efficient and compatible with the different energy sources, since they are very specific for a certain area. The present study drives its efforts towards this direction, i.e. having a system with several inputs for combining different renewable energy sources into a single and efficient power converter for the grid connection. It focuses on the design and control of an 11.7 kW hybrid renewable generation system, which contains two parallel circuits of photovoltaic panels and a wind turbine. A multicell converter divided in two stages accomplishes the convertion: Generation Side Converter (GSC) and Mains Side Converter (MSC). Two boost converters responsible for the photovoltaic generation and a rectifier and a third boost, for the wind constitue the GSC. It allows the conversion to the fixed output DC voltage, controlling individually and performing the maximum power point tracking in each input. On the other side, the single-phase 4- cell MSC accomplishes the connection to the grid through an LCL filter. This filter uses an Intercell Transformer (ICT) in the first inductor for reducing the individual ripple generated by the swicthing. The MSC controls the DC-link voltage and, by doing that, it allows the power flow from the generation elements to the network

Etude de la Commande et de l'Observation d'une Nouvelle Structure de Conversion d'Energie de type SMC (Convertisseur Multicellulaire Superposé)

Ce manuscrit apporte une contribution à la commande et à l'observation du convertisseur multicellulaire superposé (SMC). Cette nouvelle structure de conversion d'énergie, brevetée en 2001, présente des caractéristiques très intéressantes qui lui confèrent un intérêt certain pour les applications industrielles de forte puissance. Les présents travaux ont pour objet principal d'améliorer le fonctionnement des convertisseurs SMC et de montrer leur compétitivité pour ce domaine d'application. Cet enjeu est atteint de deux manières différentes mais complémentaires : en positionnant le SMC dans le domaine basse tension/forte puissance, une gamme de tension réduite par rapport à son domaine de prédilection ; en développant des techniques d'observation des tensions internes de la structure, afin de réduire son coût et d'assurer son fonctionnement optimal et sécurisé. La première partie de ce mémoire est consacrée à la présentation du fonctionnement, de la commande et des propriétés associées aux principales structures multiniveaux. Il s'agit de montrer l'intérêt que représente la topologie SMC dans les systèmes de conversion de puissance vis-à-vis des autres convertisseurs de cette famille. Nous effectuons ensuite une étude comparative des pertes, performances et coûts des topologies d'onduleurs 2 et 3 niveaux à base d'IGBT pour une application basse tension/forte puissance. L'enjeu consiste à légitimer l'utilisation du SMC à ce niveau de tension par rapport aux topologies classiques et multiniveaux concurrentes. La deuxième partie de ce manuscrit est dédiée à l'observation fine en temps réel des tensions internes de la structure SMC. Le contrôle actif de ces dernières revêt en effet un caractère important, car il conditionne la survie du convertisseur en garantissant une répartition équilibrée des contraintes en tension sur les semi-conducteurs de puissance. Cet équilibrage actif nécessite la connaissance de ces grandeurs à l'échelle de la période de découpage. La suppression des capteurs différentiels nécessaires permettrait donc de réduire de manière significative le coût global de ces structures dans le cadre d'applications industrielles. Nous présentons ainsi trois méthodes d'estimation : un reconstructeur de tension, une structure d'observation basée sur une simulation numérique en temps réel du système associée à une mesure de tension et un observateur à modes glissants. Ces techniques sont toutes validées par simulation sur des structures multicellulaires superposées à 3 cellules de commutation. L'observateur à modes glissants est également validé expérimentalement pour un onduleur SMC 7 niveaux triphasé 15kVA. Son implantation est réalisée à l'aide d'une carte numérique associant un DSP et un FPGA. ABSTRACT : This PhD Thesis deals with the control and the observation of Stacked Multicell Converters (SMC). Developed and validated within the LEEI at the beginning of years 2000, the SMC topology benefits from outstanding dynamic performances that dedicates it to medium voltage and high power applications. This manuscript tends to optimise the operation of this particular converter and to confirm its competitiveness with respect to other multilevel structures. This objective is achieved by different but complementary issues: legitimating the SMC for low voltage and high power applications and observing the flying capacitor voltages of the converter so as to reduce the topology cost and guarantee its safe and optimal operation. The first part of this thesis details the operation, the control strategy and the properties of the main multilevel topologies, in order to underline the SMC advantages for power conversion systems. A comparative study of the losses, performances and costs of IGBT-based 2 and 3-level topologies is then carried out for a particular low voltage and high power application. The main objective is to legitimate the use of the SMC converter even for this voltage range, compared to other classical and multilevel competitive structures. The second part is dedicated to the real-time observation of the SMC flying capacitor voltages. This topology indeed relies on flying capacitors so as to equally share the voltage constraint on several power switches. Balancing those internal voltages is a major issue, since it determines the lifetime of the converter. Removing the differential sensors required by the active control would result in a significant reduction of the topology cost for industrial applications. Three estimation methods are therefore introduced: a voltage reconstruction, a digital real time simulation of the converter combined with a voltage measurement and a sliding mode observer. Those techniques are validated by simulation for a 7-level Stacked Multicell Converter. The sliding mode observer is also confirmed experimentally with our 15kVA three-phase 7-level SMC prototype. Its implementation is realised using a digital board that combines a DSP and a FPGA

Electric Vehicle Efficient Power and Propulsion Systems

Vehicle electrification has been identified as one of the main technology trends in this second decade of the 21st century. Nearly 10% of global car sales in 2021 were electric, and this figure would be 50% by 2030 to reduce the oil import dependency and transport emissions in line with countries’ climate goals. This book addresses the efficient power and propulsion systems which cover essential topics for research and development on EVs, HEVs and fuel cell electric vehicles (FCEV), including: Energy storage systems (battery, fuel cell, supercapacitors, and their hybrid systems); Power electronics devices and converters; Electric machine drive control, optimization, and design; Energy system advanced management methods Primarily intended for professionals and advanced students who are working on EV/HEV/FCEV power and propulsion systems, this edited book surveys state of the art novel control/optimization techniques for different components, as well as for vehicle as a whole system. New readers may also find valuable information on the structure and methodologies in such an interdisciplinary field. Contributed by experienced authors from different research laboratory around the world, these 11 chapters provide balanced materials from theorical background to methodologies and practical implementation to deal with various issues of this challenging technology. This reprint encourages researchers working in this field to stay actualized on the latest developments on electric vehicle efficient power and propulsion systems, for road and rail, both manned and unmanned vehicles

Advance control of multilevel converters for integration of distributed generation resources into ac grid

Premi extraordinari doctorat curs 2011-2012, àmbit d’Enginyeria IndustrialDistributed generation (DG) with a converter interface to the power grid is found in many of the green power resources applications. This dissertation describes a multi-objective control technique of voltage source converter (VSC) based on multilevel converter topologies, for integration of DG resources based on renewable energy (and non-renewable energy)to the power grid. The aims have been set to maintain a stable operation of the power grid, in case of di erent types of grid-connected loads. The proposed method provides compensation for active, reactive, and harmonic load current components. A proportional-integral (PI) control law is derived through linearization of the inherently non-linear DG system model, so that the tasks of current control dynamics and dc capacitor voltage dynamics become decoupled. This decoupling allows us to control the DG output currents and the dc bus voltage independently of each other, thereby providing either one of these decoupled subsystems a dynamic response that signi cantly slower than that of the other. To overcome the drawbacks of the conventional method, a computational control delay compensation method, which delaylessly and accurately generates the DG reference currents, is proposed. The rst step is to extract the DG reference currents from the sensed load currents by applying the stationary reference frame and then transferred into synchronous reference frame method, and then, the reference currents are modi ed, so that the delay will be compensated. The transformed variables are used in control of the multilevel voltage source converter as the heart of the interfacing system between DG resources and power grid. By setting appropriate compensation current references from the sensed load currents in control circuit loop of DG link, the active, reactive, and harmonic load current components will be compensated with fast dynamic response, thereby achieving sinusoidal grid currents in phase with load voltages while required power of loads is more than the maximum injected power of the DG resources. The converter, which is controlled by the described control strategy, guarantees maximum injection of active power to the grid continuously, unity displacement power factor of power grid, and reduced harmonic load currents in the common coupling point. In addition, high current overshoot does not exist during connection of DG link to the power grid, and the proposed integration strategy is insensitive to grid overload.La Generació Distribuïda (DG) injectada a la xarxa amb un convertidor estàtic és una solució molt freqüent en l'ús de molts dels recursos renovables. Aquesta tesis descriu una técnica de control multi-objectiu del convertidor en font de tensió (VSC), basat en les topologies de convertidor multinivell, per a la integració de les fonts distribuïdes basades en energies renovables i també de no renovables.Els objectius fixats van encaminats a mantenir un funcionament estable de la xarxa elèctrica en el cas de la connexió de diferents tipus de càrregues. El mètode de control proposat ofereix la possibilitat de compensació de les components actives i reactives de la potencia, i les components harmòniques del corrent consumit per les càrregues.La llei de control proporcional-Integral (PI) s’obté de la linearització del model inherentment no lineal del sistema, de forma que el problema de control del corrent injectat i de la tensió d’entrada del convertidor queden desacoblats. Aquest desacoblament permet el control dels corrents de sortida i la tensió del bus de forma independent, però amb un d’ells amb una dinàmica inferior.Per superar els inconvenients del mètode convencional, s’usa un retard computacional, que genera les senyals de referència de forma acurada i sense retard. El primer pas es calcular els corrents de referència a partir de les mesures de corrent. Aquest càlcul es fa primer transformant les mesures a la referència estacionaria per després transformar aquests valors a la referència síncrona. En aquest punt es on es poden compensar els retards.Les variables transformades son usades en els llaços de control del convertidor multinivell. Mitjançant aquests llaços de control i les referències adequades, el convertidor és capaç de compensar la potencia activa, reactiva i els corrents harmònics de la càrrega amb una elevada resposta dinàmica, obtenint uns corrents de la xarxa de forma completament sinusoïdal, i en fase amb les tensions.El convertidor, controlat amb el mètode descrit, garanteix la màxima injecció de la potencia activa, la injecció de la potencia reactiva per compensar el factor de potencia de la càrrega, i la reducció de les components harmòniques dels corrents consumits per la càrrega. A més, garanteix una connexió suau entre la font d’energia i la xarxa. El sistema proposat es insensible en front de la sobrecarrega de la xarxaAward-winningPostprint (published version

Design and Control of Power Converters 2019

In this book, 20 papers focused on different fields of power electronics are gathered. Approximately half of the papers are focused on different control issues and techniques, ranging from the computer-aided design of digital compensators to more specific approaches such as fuzzy or sliding control techniques. The rest of the papers are focused on the design of novel topologies. The fields in which these controls and topologies are applied are varied: MMCs, photovoltaic systems, supercapacitors and traction systems, LEDs, wireless power transfer, etc

Industrial and Technological Applications of Power Electronics Systems

The Special Issue "Industrial and Technological Applications of Power Electronics Systems" focuses on: - new strategies of control for electric machines, including sensorless control and fault diagnosis; - existing and emerging industrial applications of GaN and SiC-based converters; - modern methods for electromagnetic compatibility. The book covers topics such as control systems, fault diagnosis, converters, inverters, and electromagnetic interference in power electronics systems. The Special Issue includes 19 scientific papers by industry experts and worldwide professors in the area of electrical engineering

Investigation of different methods of online impedance spectroscopy of batteries

A key challenge in a battery energy storage system is understanding the availability and reliability of the system from the perspective of the end customer. A key task in this process is recognising when a battery or a module within a system starts to degrade and then mitigating against this using the control system or battery management system. Battery characterisation parameters such as internal impedance and state of health and state of charge of the battery are a useful representation of the battery conditions. This thesis investigates the feasibility of undertaking Electrochemical Impedance Spectroscopy (EIS) methods online to generate an understanding of battery impedance. In order to perform an EIS measurement, an excitation signal of fixed frequency must be generated and the voltage and current measured and used to calculate the impedance. This thesis proposed different methods of generating a low-frequency excitation signal using hardware found in most battery systems to extract the harmonic impedance of a battery cell to aim towards a low cost on-line impedance estimation. This work focuses on producing impedance spectroscopy measurements through the power electronics system, a battery balancing system and the earth leakage monitoring system to attempt to get comparable results to off-line EIS measurements under similar conditions. To generate an excitation signal through the power electronic circuit, different control methods were used including varying; the duty cycle, the switching frequency and the starting position of the switched wave and the addition of an impulse type function. Although utilising a variable duty cycle to generate a harmonic impedance has been previously published in literature, the other techniques analysed within this these have not previously been considered. The thesis looks at the theoretical analysis of the circuits and control techniques and then follows this up with simulation and experimental studies. The results showed that all the methods investigated have the capability to generate a low frequency perturbation signal to undertake online EIS measurement. However, there are potential trade-offs, for example increased inductor ripple current. Not all of the methods produce sufficiently accurate results experimentally .However, five of the methods were used to generate EIS plots similar to those undertaken offline

Carga eletrônica ativa trifásica

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2013.Neste trabalho estão apresentados os estudos efetuados do conversor trifásico bidirecional de três níveis (NPCm), aplicado a operação como Carga Eletrônica Ativa de corrente alternada. Os esforços de corrente e de tensão são analisados, modelados e comparados com o conversor NPC, bem como as perdas dos seus dispositivos semicondutores, para variações da defasagem da corrente e do índice de modulação. Semicondutores estado da arte foram ensaiados em laboratório e utilizados nos dois conversores, tais como os modernos diodos e transistores de Carboneto de Silício (SiC), visando a análise comparativa das perdas e a obtenção de conversores de alta eficiência. São obtidos modelos para o sistema quando composto por filtros de primeira ou de terceira ordem, apresentando os problemas inerentes de cada topologia. No caso do filtro de primeira ordem, composto por um indutor, são apresentados vários resultados de simulação com o controle da corrente drenada, para diferentes frequências harmônicas, mostrando a possibilidade de ocorrência de saturação do controlador e como contorná-la. Para o caso de utilização de um filtro de terceira ordem (LCL), é proposto um sistema de controle formado por um controlador clássico, a Realimentação dos Estados (RE) e um Observador de Estados (OE). O observador é usado para obter o valor da variável a ser controlada, sem o uso de sensores, e a RE é usada para se obter uma amortização ativa das oscilações na frequência de ressonância do filtro. Neste caso, primeiro são apresentados resultados de simulação com o sistema de controle analógico, depois são analisados os problemas causados pela discretização e implementação com controladores digitais, mostrando qual a ação foi tomada para contornar tais problemas. Por fim, vários resultados experimentais com o controlador digital são apresentados, mostrando que o protótipo construído foi capaz de emular correntes com conteúdo harmônico amplo e genérico, com boa rejeição às perturbações causadas pelas alterações da tensão ou da indutância do equipamento sob teste (EST).Abstract : This work presents a study of a modified Neutral Point Clamped (here called NPCm), a bi-directional three-phase three-levels inverter, operating as an AC Active Electronic Load. First, the current and voltage stresses are analyzed, modelled and compared with the standard Neutral Point Clamped (NPC) inverter. State-of-the-art semiconductors were selected and tested in different controlled temperature of operation, in order to obtain their energy losses characteristics, like the modern silicon carbide (SiC) diodes and transistors. Later, this devices were used as main power semiconductors for both inverter topologies and their losses were compared as function of load current and modulation index variations, in order to achieve best performance on efficiency and same time establishing know how on its usage and power losses qualification. Models are obtained for the system when with first or third order filters were used, showing inherent characteristics of each topology. In the case of the first order filter with an inductor, several simulation results are presented with current control for various harmonic frequencies, showing the possible occurrence of controller saturation and how to avoid it. In the case of utilization of a third order filter (LCL type), this work proposes a digitally implemented control strategy comprising state feedback, robust observer, phase-locked loop and a linear current controller to cope with AC AEL applications. The observer is used to obtain the value of variable to be controlled, without the utilization of sensors and the state feedback is used to obtain an active damping of oscillations at the resonance frequency. First the simulations results are presented with an analog control, later is the problems caused by the digital controllers discretization and implementation are analysed, showing how the build prototype was able to control currents with broad and generic harmonic content showing good rejection of the perturbations caused by changes on voltage or inductance of the equipment under test (EUT)