Identification and modelling of two phase dc-dc boost converter based on autoregressive moving average with exogenous, output-error and transfer function model structures

This research presents the identification and modelling of a two-phase DC-DC boost converter based on the autoregressive moving average with exogenous (ARMAX), output-error (OE) and transfer function (TF) model structures for low-voltage applications. The goals that led to this study were to reduce the time taken to design the controller and analyse the output of constant Kp and Ki generated from the auto tuning method. A two-phase boost converter employs as 180-degree phase shift from each phase to drive the power switch. This research focused more on the system identification approach to generate mathematical models from the open-loop response. The generated models were from the TF, ARMAX and OE model structures. The mathematical models were generated from the pulse-width modulation (PWM) input and voltage output of the two-phase boost converter itself in the time domain data. After the best model order was found to replace the two�phase boost converter with a mathematical model, the controller design took place. Some closed-loop blocks were designed for the mathematical models in MATLAB/Simulink software, which were also used to perform the auto-tuning of the proportional-integral (PI) controller. However, tuning methods such as the Ziegler-Nichols and the Cohen-Coon methods are more time-consuming. After the best values for constants Kp and Ki were determined, the values were used in the real hardware to analyse the output responses. The findings showed that Kp and Ki from the TF model showed 19% overshoot compared with those of the ARMAX and OE models, which were 25.36% and 24.6%, respectively. All of the output responses from the different Kp and Ki values resulted in less than 5% ripple voltage. It can be concluded that the best model from the system identification approach was the TF system model, since it had the lowest overshoot and the lowest percentage of output voltage rippl

A review on non-isolated low-power DC-DC converter topologies with high output gain for solar photovoltaic system applications

The major challenges of the high-gain DC–DC boost converters are high-voltage stress on the switch, extreme duty ratio operation, diode reverse-recovery and converter efficiency problems. There are many topologies of high-gain converters that have been widely developed to overcome those problems, especially for solar photovoltaic (PV) power-system applications. In this paper, 20 high-gain and low-power DC–DC converter topologies are selected from many topologies of available literature. Then, seven prospective topologies with conversion ratios of >15 are thoroughly reviewed and compared. The selected topologies are: (i) voltage-multiplier cell, (ii) voltage doubler, (iii) coupled inductor, (iv) converter with a coupled inductor and switch capacitor, (v) converter with a switched inductor and switched capacitor, (vi) cascading techniques and (vii) voltage-lift techniques. Each topology has its advantages and disadvantages. A comparison of the seven topologies is provided in terms of the number of components, hardware complexity, maximum converter efficiency and voltage stress on the switch. These are presented in detail. So, in the future, it will be easier for researchers and policymakers to choose the right converter topologies and build them into solar PV systems based on their needs

Estudo comparativo de dois conversores Boost quadrático com comutação suave monochaveados para aplicação de rastreamento de máxima potência em sistemas fotovoltaicos

This paper makes a comparative study of two Soft Single Switched Quadratic Boost Converters (SSS1 and SSS2) focused on Maximum Power Point Tracking (MPPT) of a PV array using Perturb and Observe (P&O) algorithm. The proposed converters maintain the static gain characteristics and dynamics of the original converter with the advantage of considerably reducing the switching losses and Electromagnetic Interference (EMI). It is displayed the input voltage Quadratic Boost converter modeling; qualitative and quantitative analysis of soft switching converters, defining the operation principles, main waveforms, time intervals and the state variables in each operation steps, phase planes of resonant elements, static voltage gain expressions, analysis of voltage and current efforts in semiconductors and the operational curves at 200 W to 800 W. There are presented project of PI, PID and PID + Notch compensators for MPPT closed-loop system and resonant elements design. In order to analyze the operation of a complete photovoltaic system connected to the grid, it was chosen to simulate a three-phase inverter using the P-Q control theory of three-phase instantaneous power. Finally, the simulation results and experimental with the necessary comparative analysis of the proposed converters will be presented.Conselho Nacional de Desenvolvimento Científico e TecnológicoTese (Doutorado)Este trabalho faz um estudo comparativo de dois conversores Boost Quadrático monochaveados suavemente (Soft Single Switched – SSS1 e SSS2) com foco na aplicação de rastreamento de máxima potência (Maximum Power Point Tracking - MPPT) de um arranjo fotovoltaico utilizando a técnica P&O (Perturb and Observe). Os conversores propostos mantêm as características de ganho e dinâmica do conversor original, com a vantagem de reduzir consideravelmente as perdas por comutação e por irradiação de ruídos eletromagnéticos (EMI). É apresentada a modelagem do conversor Boost Quadrático para controle da tensão de entrada, a análise qualitativa e quantitativa dos conversores com comutação suave, contemplando os princípios de operação, principais formas de onda teóricas, expressões para cálculo dos intervalos de tempo e das variáveis de estado em cada etapa de operação, os planos de fase dos elementos ressonantes, o equacionamento do ganho estático de tensão, a análise dos esforços de tensão e corrente nos semicondutores e as curvas de operação do conversor na faixa de 200 W a 800 W. São apresentados roteiros de projeto para compensadores PI, PID e PID+Notch para o sistema MPPT em malha fechada e os roteiros de dimensionamento dos elementos ressonantes das células de auxílio à comutação. Com o intuito de analisar o funcionamento de um sistema fotovoltaico completo conectado à rede, escolheu-se simular um Inversor Trifásico utilizando a teoria P-Q de controle de potências instantâneas trifásicas. Por fim, serão apresentados os resultados de simulação e experimentais com as devidas análises comparativas entre os conversores propostos

High step up DC-DC converter topology for PV systems and electric vehicles

This thesis presents new high step-up DC-DC converters for photovoltaic and electric vehicle applications. An asymmetric flyback-forward DC-DC converter is proposed for the PV system controlled by the MPPT algorithm. The second converter is a modular switched-capacitor DC-DC converter, it has the capability to operate with transistor and capacitor open-circuit faults in every module. The results from simulations and tests of the asymmetric DC-DC converters have suggested that the proposed converter has a 5% to 10% voltage gain ratio increased to the symmetric structures among 100W – 300W power (such as [3]) range while maintaining efficiency of 89%-93% when input voltage is in the range of 25 – 30 V. they also indicated that the softswitching technique has been achieved, which significantly reduce the power loss by 1.7%, which exceeds the same topology of the proposed converter without the softswitching technique. Moreover, the converters can maintain rated outputs under main transistor open circuit fault situation or capacitor open circuit faults. The simulation and test results of the proposed modularized switched-capacitor DC-DC converters indicate that the proposed converter has the potential of extension, it can be embedded with infinite module in simulation results, however, during experiment. The sign open circuit fault to the transistors and capacitors would have low impact to the proposed converters, only the current ripple on the input source would increase around 25% for 4-module switched-capacitor DC-DC converters. The developed converters can be applied to many applications where DC-DC voltage conversion is alighted. In addition to PVs and EVs. Since they can ride through some electrical faults in the devices, the developed converter will have economic implications to improve the system efficiency and reliability

Otimização meta heurística e controle baseado no modelo interno aplicados em sistemas de geração fotovoltaica conectados à rede elétrica monofásica

This paper presents the study, development and application of new control techniques for photovoltaic power generation systems, connected to single-phase power grid in order to improve the efficiency of these systems in relation to control methods typically used. The work is divided into two main parts, which are related to tracking the maximum power point (Maximum Power Point Tracking - MPPT) and then the internal controller of boost quadratic converters - side of the photovoltaic panels - as well as the controllers the voltage inverter, the side of the single-phase mains. The first part of the work is the development of a heuristic goal algorithm for MPPT, which is based on the method of simulated annealing (Simulated Annealing - SA) and aims at determining the overall maximum point, seeking out solutions in a close vicinity, so as to prevent the docking local maxima in the curve of power output of the photovoltaic array, thereby improving the utilization of energy in partial shading situations. The second part presents the design of controllers based on internal model (Internal Model Control - IMC) with 1 degree of freedom (1 Degree of Freedom - 1 DOF) applied, first, the DC-DC Boost Quadratic converter, used for MPPT, and thereafter, a voltage inverter with LCL filter connected to the single phase power supply operating in current injection mode. A mathematical modeling of both converters and analyzed the compensation of internal feedback to the voltage inverter system corresponding to the disconnection of the mains voltage through the power strategy a head (feedforward). A basis of comparison for the performance analysis of IMC-1DOF converter is aiming at, is also applied to the current injection system, Proportional-Resonant Controller (P + Res). They are presented computer simulation and experimental results of both controllers, which allow you to check the system performance in low and non-linear local load network situation.Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorTese (Doutorado)Este trabalho apresenta o estudo, desenvolvimento e aplicação de novas técnicas de controle aos sistemas de geração de energia fotovoltaica, conectados à rede elétrica monofásica, visando a melhoria da eficiência destes sistemas em relação aos métodos de controle tipicamente utilizados. O trabalho é dividido em duas partes principais, as quais estão relacionadas ao rastreamento do ponto de máxima potência (Maximum Power Point Tracking – MPPT) e, depois, ao controlador interno dos conversores boost-quadrático – lado dos painéis fotovoltaicos – assim como aos controladores do inversor de tensão, no lado da rede elétrica monofásica. A primeira parte do trabalho consiste no desenvolvimento de um algoritmo de meta heurística para o MPPT, o qual é baseado no método do recozimento simulado (Simulated Annealing - SA) e tem como objetivo a determinação do ponto de máximo global, buscando soluções fora de uma vizinhança próxima, de modo a evitar o atracamento em máximos locais da curva de potência de saída do arranjo de painéis fotovoltaicos, melhorando, assim, o aproveitamento da energia em situações de sombreamento parcial. A segunda parte do trabalho apresenta o projeto de controladores baseados no modelo interno (Internal Model Control – IMC) com 1 grau de liberdade (1 Degree of Freedom – 1 DOF) aplicados, primeiramente, ao conversor CC-CC Boost Quadrático, utilizado para o MPPT, e, posteriormente, a um inversor de tensão com filtro LCL, conectado à rede elétrica monofásica, operando no modo de injeção de corrente. É apresentada a modelagem matemática de ambos os conversores e analisada a compensação da realimentação interna ao sistema do inversor de tensão, correspondente ao desacoplamento da tensão da rede, através da estratégia de alimentação à frente (Feedforward). Visando-se uma base de comparação, para a análise de desempenho do conversor IMC – 1DOF, também é aplicado ao sistema de injeção de corrente, o controlador Proporcional-Ressonante (P+Res). São apresentados resultados de simulação computacional e experimentais de ambos os 8 controladores, os quais permitem verificar o desempenho do sistema em situação de rede fraca e carga local não-linear

Isolated Single-stage Power Electronic Building Blocks Using Medium Voltage Series-stacked Wide-bandgap Switches

The demand for efficient power conversion systems that can process the energy at high power and voltage levels is increasing every day. These systems are to be used in microgrid applications. Wide-bandgap semiconductor devices (i.e. Silicon Carbide (SiC) and Gallium Nitride (GaN) devices) are very promising candidates due to their lower conduction and switching losses compared to the state-of-the-art Silicon (Si) devices. The main challenge for these devices is that their breakdown voltages are relatively lower compared to their Si counterpart. In addition, the high frequency operation of the wide-bandgap devices are impeded in many cases by the magnetic core losses of the magnetic coupling components (i.e. coupled inductors and/or high frequency transformers) utilized in the power converter circuit. Six new dc-dc converter topologies are propose. The converters have reduced voltage stresses on the switches. Three of them are unidirectional step-up converters with universal input voltage which make them excellent candidates for photovoltaic and fuel cell applications. The other three converters are bidirectional dc-dc converters with wide voltage conversion ratios. These converters are very good candidates for the applications that require bidirectional power flow capability. In addition, the wide voltage conversion ratios of these converters can be utilized for applications such as energy storage systems with wide voltage swings

Conversores CC-CC básicos não-isolados quadráticos de três níveis

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.Este trabalho introduz uma nova célula de comutação formada por dois diodos, dois interruptores comandados, dois indutores e um capacitor. Conectada adequadamente aos terminais de uma fonte de tensão (entrada) e de uma carga, as três principais topologias dos conversores CC-CC básicos não-isolados são concebidas: buck, boost e buck-boost. A célula de comutação proposta, juntamente com uma modulação apropriada dos dois interruptores, atribui aos conversores duas características muito importantes: em nenhum instante a tensão sobre cada interruptor atinge o maior valor envolvido na conversão (entrada no buck e saída no boost) ou a soma das tensões de entrada e saída (buck-boost), e o ganho estático varia com o quadrado da razão cíclica, tornando-os atrativos em ganhos altos, especialmente o conversor boost. Além disso, o fato de haver dois interruptores acrescenta aos conversores um grau de liberdade a mais em relação às topologias convencionais, representado pelo parâmetro a. Para cada conversor foi realizada uma análise teórica detalhada, incluindo etapas de operação, ganho estático ideal, principais formas de onda, ondulação de corrente nos indutores e de tensão nos capacitores, bem como a característica externa, matemática e graficamente. Os três conversores foram montados e as principais formas de onda adquiridas a fim de validar a teoria apresentada

High gain non-isolated DC-DC converter topologies for energy conversion systems

PhD ThesisEmerging applications driven by low voltage level power sources, such as photovoltaics, batteries and fuel cells require static power converters for appropriate energy conversion and conditioning to supply the requirements of the load system. Increasingly, for applications such as grid connected inverters, uninterruptible power supplies (UPS), and electric vehicles (EV), the performance of a high efficiency high static gain power converter is of critical importance to the overall system. Theoretically, the conventional boost and buck-boost converters are the simplest non-isolated topologies for voltage step-up. However, these converters typically operate under extreme duty ratio, and severe output diode reverse recovery related losses to achieve high voltage gain. This thesis presents derivation, analysis and design issues of advanced high step-up topologies with coupled inductor and voltage gain extension cell. The proposed innovative solution can achieve significant performance improvement compared to the recently proposed state of the art topologies. Two unique topologies employing coupled inductor and voltage gain extension cell are proposed. Power converters utilising coupled inductors traditionally require a clamp circuit to limit the switch voltage excursion. Firstly, a simple low-cost, high step-up converters employing active and passive clamp scheme is proposed. Performance comparison of the clamps circuits shows that the active clamp solution can achieve higher efficiency over the passive solution. Secondly, the primary detriment of increasing the power level of a coupled inductor based converters is high current ripple due to coupled inductor operation. It is normal to interleaved DC-DC converters to share the input current, minimize the current ripple and increase the power density. This thesis presents an input parallel output series converter integrating coupled inductors and switched capacitor demonstrating high static gain. Steady state analysis of the converter is presented to determine the power flow equations. Dynamic analysis is performed to design a closed loop controller to regulate the output voltage of the interleaved converter. The design procedure of the high step-up converters is explained, simulation and experimental results of the laboratory prototypes are presented. The experimental results obtained via a 250 W single phase converter and that of a 500 W interleaved converter prototypes; validate both the theory and operational characteristics of each power converter.Petroleum Technology Development Fund (PTDF) Nigeri

Conversores CC-CC com elevada taxa de conversão estática

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Elétrica, Florianópolis, 2014.Nesse trabalho é introduzida uma nova família de Conversores CC-CC com elevada taxa de conversão estática. Tais conversores tem origem a partir dos Conversores CC-CC básicos convencionais (Buck, Boost, Buck-Boost, Zeta, Cúk e Sepic), no qual inserindo a célula básica de comutação proposta no trabalho, é possível tornar esses conversores convencionais em conversores com elevada taxa de conversão estática, gerando os Conversores Propostos. A célula de comutação responsável por gerar a família de Conversores Propostos possui apenas semicondutores passivos, o que é uma vantagem para essas topologias. Além disso, a família de Conversores Propostos possui a vantagem de ser simétrica, isso possibilita a reflexão dos componentes superiores, gerando os componentes inferiores das novas estruturas. Essa reflexão é uma característica importante nas topologias propostas, pois reduz os esforços de tensão em seus interruptores. Seguindo a nomenclatura básica, os conversores propostos são chamados de: Duplo Buck Quadrático, Duplo Boost Quadrático, Duplo Buck-Boost Quadrático, Duplo Zeta Quadrático, Duplo Cúk Quadrático e Duplo Sepic Quadrático. Dos sete Conversores Propostos no trabalho, somente um não é originado pela célula básica de comutação. Este Conversor é chamado de Duplo Buck Quadrático Básico, e foi importante para consolidar os estudos dos Conversores CC-CC com elevada taxa de conversão estática. Algumas análises como etapas de operação em condução contínua, ganho estático e característica externa são apresentadas para todos os conversores propostos. Para provar as análises teóricas, os resultados experimentais em malha aberta são apresentados para o Conversor Duplo Buck Quadrático Básico, e em malha aberta, malha fechada e malha fechada com desequilíbrio de carga para o Conversor Duplo Boost Quadrático.<br