Este trabalho propõe a adoção de uma estrutura de controle, com base na tese de doutorado de (BUEHNER, 2010), a qual utiliza um modelo com a dinâmica inversa da planta a ser controlada, de maneira a prover a pré-alimentação da tensão de referência para o controle de um conversor de potência monofásico, modulado por largura de pulso (PWM), obtendo-se bons resultados para o rastreamento da corrente do indutor de filtro conectado à saída deste conversor de potência. No trabalho, são apresentadas outras duas estruturas de controle por pré-alimentação, responsáveis respectivamente pelo cancelamento da perturbação gerada pela tensão na saída do filtro indutivo e pelo cancelamento do erro de tensão gerado pelo tempo morto. Com o intuito de assegurar o desempenho de rastreamento da corrente, face às variações de parâmetros do processo e as imperfeições existentes no modelamento da planta real, emprega-se a estrutura de controle proporcional, em malha fechada, assegurando a robustez da estrutura de controle, facilitando-se o ajuste da malha de controle. Os resultados de simulação e obtidos experimentalmente são comparados, validando-se efetivamente a estratégia de controle proposta. / This work presents the control structure based on (BUEHNER, 2010) PhD thesis, which uses an inverse dynamic model for the plant to be controlled, providing the feedforward voltage reference to control a single-phase, pulse width modulated power converter (VSI-PWM), achieving good results for the output inductor current tracking, connected on the power converter output. Two feedforward control structures are presented, for the cancellation of the voltage disturbance generated by the output filter voltage and the cancellation of voltage error generated by the dead time implementation, respectively. In order to ensure the current tracking performance in face of process parameter variations and modeling imperfections existing in the real plant, the closed loop proportional is employed under the proposed control structure, ensuring the control robustness, and facilitating the loop gain adjustments. The simulation and experimental results are obtained and compared, effectively evaluating the proposed control strategy.

A crescente utilização de cargas sensíveis em aplicações industriais, atualmente tem levado a uma preocupação real devido aos custos provocados por interrupções e danos causados a linhas de produção automatizadas. Este trabalho apresenta uma solução baseada em sistemas de eletrônica de potência capaz de compensar Voltage Sags, Voltage Swells e distorções harmônicas de tensão, restaurando a tensão da carga a valores aceitáveis através de um transformador de injeção conectado em série entre a rede e a carga. As características de projeto para um protótipo de Restaurador Dinâmico de Tensão (DVR) são detalhadas, estratégias de controle são comparadas e uma das alternativas é implementada em um DSP (Digital Signal Processor). Finalmente, resultados experimentais de um protótipo de 5kVA são apresentados. / The increasing use of voltage sensitive loads on industrial applications has led to a real concern about interruption costs and damages on automatic production lines. This work presents a power-electronic-based device which compensates Voltage Sags, Voltage Swells and Voltage Harmonic Distortion, restoring the load voltage to acceptable values through a series connected injection transformer. The ratings and power requirements of a Dynamic Voltage Restorer (DVR) are derived, as well as its control algorithm implemented in a Digital Signal Processor (DSP). Finally, simulation and experimental results of a 5kVA prototype are presented.

O objetivo deste trabalho é analisar uma topologia de controle para a malha de tensão de um inversor para fontes de alimentação ininterruptas (UPS) com forma de onda senoidal na saída. É proposto um sistema de controle com duas malhas, uma de tensão com controlador ressonante e outra do tipo PI de corrente no qual a variável de controle é a corrente do capacitor de filtro de saída. Mais especificamente pretende-se estudar o problema de rastreamento de tensão nos inversores de UPS monofásicos, apresentando o estado da arte e uma classificação dos controladores que servem de solução para este problema específico. / This work analyses a uninterruptible power supply (UPS) inverter control scheme with sinusoidal output voltage. A two-loop control scheme is proposed; one voltage loop using a resonant controller and a PI current controller with the output capacitor filter current as control variable. A review on voltage tracking control in one-phase voltage source inverter is presented, showing the state of the art and a controller classification for this specific problem.

Este trabalho apresenta algumas estratégias de controle das malhas de rastreamento de tensão e corrente no lado CA de conversores do tipo fonte de tensão com filtro L ou LC. A topologia escolhida para o controle de tensão CA do inversor é a de duas malhas de controle em cascata: malha de tensão e malha de corrente, sendo esta última mais interna no sistema de controle. A metodologia de trabalho utilizada consiste na modelagem do sistema (sistema controlado e controladores), ajuste dos parâmetros do controlador, simulação computacional do sistema \"inversor + controlador\", implementação de alguns controladores propostos utilizando um DSP e testes em um sistema real com inversor. O estudo das técnicas de controle concentra-se inicialmente na estratégia de realimentação de dois estados no domínio de tempo contínuo, evoluindo para estratégias em tempo discreto que consideram o atraso na atuação do inversor devido ao tempo de cálculo do algoritmo de controle. Em tempo discreto, são analisados controladores preditivos para as malhas de tensão e corrente, bem como o emprego de controladores Proporcional-Integral (PI) na malha de tensão. Os dois últimos controladores são testados em um inversor PWM de baixa potência para diversos tipos de carga, com tensão de referência de inversor senoidal em 60Hz e referência contendo harmônicas. / This work presents some control strategies to achieve voltage and current tracking at the AC side of Voltage Source Converters with L or LC output filters. The topology of voltage control is the Multi-loop control with two loops: Voltage (outer loop) and Current Loop (inner loop). The proposed methodology consists in modeling the control system (plant and controllers), tuning of the controller parameters, simulating the complete system including inverter and controller, implementation of the proposed control strategies on a Digital Signal Processor (DSP) and tests in a power converter. The thesis is initially focused on a state variable continuous time controller with two states and then discrete-time strategies which consider the actuation delay due to the time required to evaluate the control algorithm are studied. In these discrete-time models, predictive controllers in voltage and current loops are analyzed, as well as the use of Proportional- Integral (PI) controllers in the Voltage Loop. These two last control topologies are tested in a low-power inverter for several load conditions with sinusoidal 60Hz inverter reference voltage and with harmonic distortion in the inverter reference voltage.

This thesis work aims at developing a model in Visual Basic for Applications and Microsoft Excel that can be used to predict temperatures in semiconductor devices for two commercial products made by Voith Hydro AB, and via simulation of the model determine the maximum current that can be conducted through the two products. The two products are called field exciters. A field exciter controls the rotor current of a generator with the help of semiconductor devices. When used in a power converter, such devices give rise to losses. A certain amount of the electrical energy passing through the converter is lost in form of heat. If the thermal energy is not dissipated, the temperature in the semiconductor device will rise. This will eventually lead to device failure when the temperature exceeds a certain temperature threshold which depends on the semiconductor material. The proposed model allows to predict these losses and the corresponding temperatures for a specified field current and ambient temperature. The model was validated experimentally. A simplified brushless excitation system was designed and constructed, temperature measurements were carried out for different field currents and later used to validate the model. This thesis concludes that the model developed in Visual Basic predicts temperatures with good results for the PWM-30A but not as good for the PWM-150A. The model simulations show that the PWM-30A can operate with a continuous current of 30 A, for a short duration of 10 seconds it can step up the current to 60 A at an ambient temperature of 50 °C. When the PWM-30A is cooled by forced convection, it can conduct a continuous current of 50 A at an ambient temperature of 50 °C. During field forcing, the PWM-30A can step up the current to 100 A for a duration of 10 seconds. It has been concluded that the PWM-150A cannot, without further testing, conduct a larger current than it was originally designed for, which is 150 A continuously at an ambient temperature of 40 °C. During field forcing it can step up the current to 240 A for 10 seconds.

Gallium Nitride (GaN) power devices have the potential to jump-start the next generation of power converters which are smaller, faster, denser, and cheaper. They are thus expected to meet the increasing 21st Century need for power density and efficiency, while at the same time reducing pollution. With the commercialisation of 600 V GaN power devices, which the industry is keen to adopt, come significant challenges. Since there are a number of such devices which are new to the power community, there is a steep learning curve involved, with dispersed information on how best to employ these devices. This work aims to solve this problem through the development of a universal GaN power device and circuit model and the formulation of design rules and guidelines. Through this contribution, designers will be able to better understand and work with these novel devices with relative ease. This will aid the need for faster adoption of GaN devices by the industry solving the barriers to commercialisation. This research demonstrates the use of machine learning (ML) algorithms for behavioural modelling of GaN power devices. Introducing ML as the key to developing a general behavioural and circuit model for GaN power devices combined with understanding, learning, customizing and successfully demonstrating it is the major contribution of this research work. This research first presents a comprehensive investigation into the parasitic effect on the GaN device switching performance. A simple process based on RF techniques is introduced to approximately extract the impedances of the GaN device to develop a behavioural model. The switching behaviour of the model is validated using simulation and double pulse test experiments at 450 V, 10 A test conditions. The developed behavioural model for Transhporm GaN HEMT is 95.2% accurate as the existing LT-spice manufacturer model, and is very much easier for power designers to handle, without the need for knowledge about the physics or geometry of the device. However, given that separate models would need to be developed for each commercial GaN device, the need for a generalized and accurate GaN behavioural model was identified, and it is this generalised model that the remainder of this thesis focuses on. In the next part of this research, a GaN platform test bench is built through bridging RF and power electronics design methodologies to achieve a gate loop and power loop inductance of around 1.8nH with switching waveforms with rise time and fall time around 2.5ns at 450V, 15A, 500KHz test conditions. The double pulse test circuits are customized using different off the shelf gate drives and analysed for collecting switching data for training the ML model. ML modelling using supervised learning is used to predict the switching voltage and current waveforms thus making it possible to construct a generic GaN black box model. Different architectures with single and multi- layer neural networks are explored for modelling. The ability to demonstrate a GaN device ML model that maps both voltage and current inputs and outputs is another characteristic and novel feature of this work. This research demonstrates different types of GaN ML models. The developed voltage and current prediction models are based on feed forward neural network (FFNN), long short-term memory unit (LSTM) and gated recurrent unit (GRU). Several parameters are quantified and compared for validating the models. They are the network architectures, parameters, training time, validation loss and error loss. The ML models are also compared with the demonstrated model of chapter 3 and existing LT-Spice manufacturer models. The results show that the author has been able to develop a GaN LSTM ML model with an error rate of 0.03, and convergence at 3s with excellent stability. The ML based modelling is then translated from GaN power devices to GaN based circuits. Among the different neural network architectures trained and tested, a multi FFNN with 5 hidden layers and 30 neurons, was found to be the best for prediction and optimization. The switching behaviour comparison results shows the benefits and value of ML modelling in opening up whole new possibilities of employing advanced control algorithms for very efficient, reliable and scalable performance of GaN power electronics systems. Finally, the findings of this work have been generalized to frame machine learning based techniques to address the need for generic modelling of power electronic devices. These solutions are presented as an information manual to researchers, engineers and students interested in benefiting from adopting machine learning for power electronics applications.

A crescente utilização de cargas sensíveis em aplicações industriais, atualmente tem levado a uma preocupação real devido aos custos provocados por interrupções e danos causados a linhas de produção automatizadas. Este trabalho apresenta uma solução baseada em sistemas de eletrônica de potência capaz de compensar Voltage Sags, Voltage Swells e distorções harmônicas de tensão, restaurando a tensão da carga a valores aceitáveis através de um transformador de injeção conectado em série entre a rede e a carga. As características de projeto para um protótipo de Restaurador Dinâmico de Tensão (DVR) são detalhadas, estratégias de controle são comparadas e uma das alternativas é implementada em um DSP (Digital Signal Processor). Finalmente, resultados experimentais de um protótipo de 5kVA são apresentados. / The increasing use of voltage sensitive loads on industrial applications has led to a real concern about interruption costs and damages on automatic production lines. This work presents a power-electronic-based device which compensates Voltage Sags, Voltage Swells and Voltage Harmonic Distortion, restoring the load voltage to acceptable values through a series connected injection transformer. The ratings and power requirements of a Dynamic Voltage Restorer (DVR) are derived, as well as its control algorithm implemented in a Digital Signal Processor (DSP). Finally, simulation and experimental results of a 5kVA prototype are presented.

Este trabalho propõe a adoção de uma estrutura de controle, com base na tese de doutorado de (BUEHNER, 2010), a qual utiliza um modelo com a dinâmica inversa da planta a ser controlada, de maneira a prover a pré-alimentação da tensão de referência para o controle de um conversor de potência monofásico, modulado por largura de pulso (PWM), obtendo-se bons resultados para o rastreamento da corrente do indutor de filtro conectado à saída deste conversor de potência. No trabalho, são apresentadas outras duas estruturas de controle por pré-alimentação, responsáveis respectivamente pelo cancelamento da perturbação gerada pela tensão na saída do filtro indutivo e pelo cancelamento do erro de tensão gerado pelo tempo morto. Com o intuito de assegurar o desempenho de rastreamento da corrente, face às variações de parâmetros do processo e as imperfeições existentes no modelamento da planta real, emprega-se a estrutura de controle proporcional, em malha fechada, assegurando a robustez da estrutura de controle, facilitando-se o ajuste da malha de controle. Os resultados de simulação e obtidos experimentalmente são comparados, validando-se efetivamente a estratégia de controle proposta. / This work presents the control structure based on (BUEHNER, 2010) PhD thesis, which uses an inverse dynamic model for the plant to be controlled, providing the feedforward voltage reference to control a single-phase, pulse width modulated power converter (VSI-PWM), achieving good results for the output inductor current tracking, connected on the power converter output. Two feedforward control structures are presented, for the cancellation of the voltage disturbance generated by the output filter voltage and the cancellation of voltage error generated by the dead time implementation, respectively. In order to ensure the current tracking performance in face of process parameter variations and modeling imperfections existing in the real plant, the closed loop proportional is employed under the proposed control structure, ensuring the control robustness, and facilitating the loop gain adjustments. The simulation and experimental results are obtained and compared, effectively evaluating the proposed control strategy.

Este trabalho apresenta algumas estratégias de controle das malhas de rastreamento de tensão e corrente no lado CA de conversores do tipo fonte de tensão com filtro L ou LC. A topologia escolhida para o controle de tensão CA do inversor é a de duas malhas de controle em cascata: malha de tensão e malha de corrente, sendo esta última mais interna no sistema de controle. A metodologia de trabalho utilizada consiste na modelagem do sistema (sistema controlado e controladores), ajuste dos parâmetros do controlador, simulação computacional do sistema \"inversor + controlador\", implementação de alguns controladores propostos utilizando um DSP e testes em um sistema real com inversor. O estudo das técnicas de controle concentra-se inicialmente na estratégia de realimentação de dois estados no domínio de tempo contínuo, evoluindo para estratégias em tempo discreto que consideram o atraso na atuação do inversor devido ao tempo de cálculo do algoritmo de controle. Em tempo discreto, são analisados controladores preditivos para as malhas de tensão e corrente, bem como o emprego de controladores Proporcional-Integral (PI) na malha de tensão. Os dois últimos controladores são testados em um inversor PWM de baixa potência para diversos tipos de carga, com tensão de referência de inversor senoidal em 60Hz e referência contendo harmônicas. / This work presents some control strategies to achieve voltage and current tracking at the AC side of Voltage Source Converters with L or LC output filters. The topology of voltage control is the Multi-loop control with two loops: Voltage (outer loop) and Current Loop (inner loop). The proposed methodology consists in modeling the control system (plant and controllers), tuning of the controller parameters, simulating the complete system including inverter and controller, implementation of the proposed control strategies on a Digital Signal Processor (DSP) and tests in a power converter. The thesis is initially focused on a state variable continuous time controller with two states and then discrete-time strategies which consider the actuation delay due to the time required to evaluate the control algorithm are studied. In these discrete-time models, predictive controllers in voltage and current loops are analyzed, as well as the use of Proportional- Integral (PI) controllers in the Voltage Loop. These two last control topologies are tested in a low-power inverter for several load conditions with sinusoidal 60Hz inverter reference voltage and with harmonic distortion in the inverter reference voltage.

O objetivo deste trabalho é analisar uma topologia de controle para a malha de tensão de um inversor para fontes de alimentação ininterruptas (UPS) com forma de onda senoidal na saída. É proposto um sistema de controle com duas malhas, uma de tensão com controlador ressonante e outra do tipo PI de corrente no qual a variável de controle é a corrente do capacitor de filtro de saída. Mais especificamente pretende-se estudar o problema de rastreamento de tensão nos inversores de UPS monofásicos, apresentando o estado da arte e uma classificação dos controladores que servem de solução para este problema específico. / This work analyses a uninterruptible power supply (UPS) inverter control scheme with sinusoidal output voltage. A two-loop control scheme is proposed; one voltage loop using a resonant controller and a PI current controller with the output capacitor filter current as control variable. A review on voltage tracking control in one-phase voltage source inverter is presented, showing the state of the art and a controller classification for this specific problem.