Distributed generation is expected to play a significant role in remedying the many shortcomings in today’s energy market. In particular, fuel cell power generation will play a big part due to several advantages. Still, it is faced with its own challenges to tap into its potential as a solution to the crisis. The responsibilities of the Power Conditioning Unit (PCU), and thus its design, are therefore complex, yet critical to the fuel cell system’s performance and ability to meet the requirements. To this end, the dc-dc converter, considered the most critical component of the PCU for optimum performance, is closely examined. The selected converter is first modeled to gain insight into its behavior for the purpose of designing suitable compensators. MATLAB is then used to study the results using the frequency domain, and it was observed that the converter offers its own unique challenges in terms of closed-loop performance and stability. These limitations must therefore be carefully accounted for and compensated against when designing the control loops to achieve the desired objectives. Negative feedback control to ensure robustness is then discussed. The insertion of a second inner loop in Current Mode Control (CMC) offers several key advantages over single-loop Voltage Mode Control (VMC). Furthermore, the insertion of a Current Error Amplifier (CEA) in Average Current Mode Control (ACMC) helps overcome many of the problems present in Peak Current Mode Control (PCMC) whilst allowing much needed design flexibility. It is therefore well suited for this application in an attempt to improve the dynamic behavior and overcoming the shortcomings inherent in the converter. The modulator and controller for ACMC are then modeled separately and combined with the converter’s model previously derived to form the complete small-signal model. A suitable compensation network is selected based on the models and corresponding Bode plots used to assess the system’s performance and stability. The resulting Bode plot for the complete system verifies that the design objectives are clearly met. The complete system was also built in MATLAB/Simulink, and subjected to external disturbances in the form of stepped load changes. The results confirm the system’s excellent behavior despite the disturbance, and the effectiveness of the control strategy in conjunction with the derived models. To meet the demand in many applications for power sources with high energy density and high power density, it is constructive to combine the fuel cell with an Energy Storage System (ESS). The hybrid system results in a synergistic system that brings about numerous potential advantages. Nevertheless, in order to reap these potential benefits and avoid detrimental effects to the components, a suitable configuration and control strategy to regulate the power flow amongst the various sources is of utmost importance. A robust and flexible control strategy that allows direct implementation of the ACMC scheme is devised. The excellent performance and versatility of the proposed system and control strategy are once again verified using simulations. Finally, experimental tests are also conducted to validate the results presented in the dissertation. A scalable and modular test station is built that allows an efficient and effective design and testing process of the research. The results show good correspondence and performance of the models and control design derived throughout the thesis.

In this thesis a boost converter is developed to be used as a test bench in power electronics laboratory. For this purpose, first, steady-state and small-signal analyses of a boost converter are carried out, then closed loop control of the converter is developed and simulated. Then, the circuit is designed and manufactured. The test results are compared with the simulation results. Finally, an experimantal procedure is prepared to enable the students to perform the experiment in the laboratory with the test bench developed.

Due to the differences in batteries of a series-connected battery bank, the restored capacity in each battery may not be the same when being charged. In order to extend battery cycle life, the charger for the battery bank must have the capability of charging equalization. This thesis proposes a non-dissipative balance charging circuit based on buck-boost topology for a series-connected battery bank. Each battery in a battery bank is associated with a buck-boost converter. This topology can efficiently alleviate the unbalance of charge among batteries by taking off the charge from the affluently charged batteries and then allotting to those insufficient ones. To accomplish this complicated and accurate control, a digital signal processor (DSP) with sensors and interface circuits is adopted. It monitors the variations of battery voltages, activates the associated buck-boost converter, and adjusts the duty ratio of the converter to regulate the energy to be released. In virtue of the adoption of digital control kernel, the control circuit can be simple and the control flexibility can be favored. A battery bank with four series connected lead-acid batteries is used for illustrating the operating behavior and describing the operation modes of the balance charging circuit. The results of experiments convincingly advocate the applicability of the proposed approach.

This thesis proposes a single-stage high-power-factor electronic ballast with series-resonant inverter for rapid-start fluorescent lamps with zero glow current during preheating period. A buck-boost converter is integrated into the ballast as the power-factor-corrector. Two auxiliary windings are wound on the same core of the buck-boost inductor for filament heating. During the preheating period, the buck-boost converter is initiated while the series-resonant inverter is disabled by controlling the corresponding active power switches. Due to zero voltage across the lamp, the glow current can be effectively eliminated. As the filaments reach appropriate emission temperature, the series-resonant inverter is activated. The lamp is then ignited and consequently operated at the rated lamp power. Circuit analyses and experimental tests of the proposed preheating control scheme are carried out on an electronic ballast for a T8-40W rapid-start fluorescent lamp.

A single-phase, buck-boost based, dual-output AC-DC converter is studied in this thesis. The converter has two DC outputs with opposite polarities, which share the same ground with the input power line. The power stage performance, including the input filter, is studied and procedure to select power components is given. The circuit model is analyzed to develop appropriate control. Zerocrossing distortion of the source input current is addressed and a solution is proposed. Experimental results are satisfactory in that a high power factor line current results for steady-state operation.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This dissertation presents as the main contribution the design and experimental validation of a robust H2 controller applied to boost converters with variations on the parameters load resistance, input voltage and operating point duty cycle. First, a polytopic model of the plant is presented, allowing to represent all the possible variations of the parameters within intervals previously established. Design conditions for a robust H2 controller, optimal under the quadratic stability, are detailed and used, allowing to efficiently calculate the controller gains. These gains are implemented with analog circuitry and the closed-loop system is tested by means of simulation and experimental results, which show a good match and illustrate a good performance. Finally, the small perturbation rejection capacity of the closed-loop system subject to parametric variations is evaluated using the H∞ guaranteed cost. / Esta dissertação apresenta como principal contribuição o projeto e a validação experimental de um controlador robusto H2 aplicado a conversores boost com variações nos parâmetros resistência de carga, tensão de entrada e razão cíclica do ponto de operação. Primeiramente, um modelo politópico da planta é apresentado, permitindo representar todas as situações de variações possíveis dos parâmetros mencionados, dentro de intervalos previamente estabelecidos. Condições de projeto de um controlador robusto H2, ótimo sob a estabilidade quadrática, são detalhadas e utilizadas, permitindo calcular eficientemente os ganhos do controlador. Estes ganhos são implementados de forma analógica e o sistema em malha fechada é testado por meio de resultados experimentais e de simulação, que apresentam uma boa correspondência e ilustram um bom desempenho. Por fim, a capacidade de rejeição de pequenas perturbações do sistema em malha fechada sujeito a variações paramétricas é avaliada utilizando o custo garantido H∞.

High efficiency of power converters placed between renewable energy sources and the utility grid is required to maximize the utilization of these sources. Power quality is another aspect that requires large passive elements (inductors, capacitors) to be placed between these sources and the grid. The main objective is to develop higher-level high frequency-based power converter system (HFPCS) that optimizes the use of hybrid renewable power injected into the power grid. The HFPCS provides high efficiency, reduced size of passive components, higher levels of power density realization, lower harmonic distortion, higher reliability, and lower cost. The dynamic modeling for each part in this system is developed, simulated and tested. The steady-state performance of the grid-connected hybrid power system with battery storage is analyzed. Various types of simulations were performed and a number of algorithms were developed and tested to verify the effectiveness of the power conversion topologies. A modified hysteresis-control strategy for the rectifier and the battery charging/discharging system was developed and implemented. A voltage oriented control (VOC) scheme was developed to control the energy injected into the grid. The developed HFPCS was compared experimentally with other currently available power converters. The developed HFPCS was employed inside a microgrid system infrastructure, connecting it to the power grid to verify its power transfer capabilities and grid connectivity. Grid connectivity tests verified these power transfer capabilities of the developed converter in addition to its ability of serving the load in a shared manner. In order to investigate the performance of the developed system, an experimental setup for the HF-based hybrid generation system was constructed. We designed a board containing a digital signal processor chip on which the developed control system was embedded. The board was fabricated and experimentally tested. The system’s high precision requirements were verified. Each component of the system was built and tested separately, and then the whole system was connected and tested. The simulation and experimental results confirm the effectiveness of the developed converter system for grid-connected hybrid renewable energy systems as well as for hybrid electric vehicles and other industrial applications.

Lithium-ion batteries are the most are widely used as electrical storage device in various applications such as portable electronics, electric vehicles, Photovoltaic application, telecommunication etc due to the characteristics of the batterie such as high-power density, long cycling and high-power efficiency. Extensive condition monitoring of the battery should be implemented due to the usage of the battery so that there will be an increase in all the overall performance and expectancy. This research is focused on implementing an online condition monitoring on the Li-ion battery using a signal injection through a power converter. The implemented technique in this research is known as the Electrochemical Impedance Spectroscopy (EIS). The EIS is a widely known technique used in determining the internal impedance of a battery cell. The estimated impedance can be used to determine the state of charge (Soc) and State of health (SoH) of a battery. The EIS is used to characterize the electrochemical behaviour thereby monitoring the change in the impedance of the cell of the battery. The EIS technique is accomplished by sinusoidally injecting current at different frequencies and measuring the voltage response. A standard Frequency Response Analyser (FRA) is used as an offline test while the battery is disconnected from the Load. The limitation of this standard FRA analyser is that it is bulky and Expensive. Attempts have been made to migrate the techniques to online operations, each having their own challenges. For an online Implementation, the interfacing power converter is used for Signal injection to measure the impedance of the battery. This work explores the low current ripple advantage of a threelevel boost converter to implement EIS on lithium ion battery.

The master thesis deals with the development of buck-boost DC-DC converter which supplies matrix beam module. The design is focused on testing two-phase boost converter and three channel buck converter manufactured by NXP Semiconductors. Part of the design is implementation of microcontroller for converter control and communication with computer. Part of the thesis is also to design user interface on Windows platform for easy system configuration. Next thing the thesis deals with is designing load for DC-DC converter that is variable and can make different current consumption. One part of this thesis is focused to achieve the lowest conducted emissions and to maximize conducted immunity. Part of this project is production of a prototype and prototype testing.

A boost converter is one of the most efficient techniques to step up DC input voltage to a higher needed DC output voltage. The boost converter has many possible applications, such as in a photovoltaic system, hybrid car and battery charger. The proposed prototype in this report is a proof of concept that a Two-Phase Boost Converter is a possible improvement topology to offer higher efficiency without compromising any advantages readily offered by a basic boost. The prototype is designed to be able to handle up to 200 watts of output power with an input of 36 volts and an output of 48 volts. This paper goes through step-by-step the calculation, design, build and test of a Two-Phase Boost Converter. Calculations found in this paper were done on Mathcad and the simulations were done on LTSpice and Pspice. These include converter’s efficiency and other measures of converter’s performance. Advantages, disadvantages as well as possible improvements of the proposed topology will be presented. Data collected and analyzed from the prototype were done on a bench test, not through an actual application.