계통 연계형 인버터의 최적화된 LCL-필터 설계 기법- Optimization Design Method for LCL-filter in Grid-connected Inverter Systems -AUTHOR Seong Soo Park -Department of Space Survey Information Technology Ajou University--Dissertation for doctoral degree in engineering

 Optimization Design Method for LCL-filter in Grid-connected Inverter Systems

ABSTRACT 

Autrhor Seong Soo Park -Department of Space Survey Information Technology Ajou University

 Dissertation for doctoral degree in engineering 

This study proposes an optimized design method of LCL filter in grid connected inverter system using various pulse width modulation (PWM) methods. Recently, many contries around the world are implementing low carbon policies to prevent glob al warming. Importance of new renewable energy such as photovoltaic power , fuel cells and wind power generation is coming to the fore significantly . And also many countries are interested in the development of smart grid technology because it is necessary to develop a technology which connect s distributed power sources to power systems in order to introduce renewable energy. The Smart Grid means operating an effective power network by combining ICT (Information and Communication Te chnologies) with existing power grids. As the photovoltaic power generation and fuel cell power generation are DC power generation units , they are used in conjunction with the power grid like as electrical power system with converting DC to AC using inverter The harmonics is caused by switching control of the inverter and these harmonic components should be compiled with standard of IEEE (IEEE 519, IEEE 1547.2) and also THD (Total Harmonics Distortion) of output current should be limited to within 5 % based on this standard . For this reason, it is necessary to reduce harmonics by using filters at input and output sides of the inverter. In the past, L filter was used mainly , but drawback is increasing volume and weakness of dynamic characteristic as L filter capacity is increased. Therefore, recently LC filter or LCL filter are mainly used and various studies in terms of the filter design are under progressing. LCL filter has a combined structure with L filter and LC filter of inverter and has same characteristics with the third order low pass filter, furthermore same level of harmonics can be reduced with using only small capacity compared with L filter. However, there are some disadvantages that design is complicated and unwilling resonance might be happened. This paper proposes on optimized design method of the LCL filter based on the inverter topologies and switching methods. There is no different of design value from others in the low range of voltage modulating factor but the higher tolerance is happened, the bigger voltage modulating factor is incresead, This paper shows optimized design method related to this improvements. The simulations are carried out to verify the effectiveness of the proposed methods: 3 phase 2 level, 3 level topologies and SVPWM, DPWM switching methods for the grid connected inverter. Moreover, 3kW experimental setups are used to identify the feasibility of their methods.

LINK:  https://docsplayer.org/134883058-공학박사학위논문.html

SINGLE STAGE GRID-CONNECTED MICRO-INVERTER FOR PHOTOVOLTAIC SYSTEMS by Nikhil Sukesh-Department of Electrical and Computer Engineering--Queen’s University Kingston, Ontario, Canada-

 

SINGLE STAGE GRID-CONNECTED MICRO-INVERTER FOR PHOTOVOLTAIC SYSTEMS by Nikhil Sukesh 

 A thesis submitted to the Department of Electrical and Computer Engineering In conformity with the requirements for the degree of Master of Applied Sciences Queen’s University Kingston, Ontario, Canada 

 Abstract This thesis concentrates on the design and control of a single stage inverter for photovoltaic (PV) micro-inverters. The PV micro-inverters have become an attractive solution for distributed power generation systems due to their modular approach and independent Maximum Power Point Tracking (MPPT). Since each micro-inverter has an individual inverter section, it is essential to have small-sized power conversion units. Moreover, these inverters should provide large voltage amplification in order to connect to the utility grid because of the low voltages of the PV panels. In order to operate these inverters at high frequencies, the soft-switching of the power MOSFETs is an important criterion to minimize the switching losses during the power transfer. A novel Zero Voltage Switching (ZVS) scheme to improve the efficiency of a single stage grid-connected flyback inverter is proposed in this thesis. The proposed scheme eliminates the need for auxiliary circuits to achieve soft-switching for the primary switch. ZVS is realized by allowing the current from the grid-side to flow in a direction opposite to the actual power transfer with the help of bi-directional switches placed on the secondary side of the transformer. The negative current discharges the output capacitor of the primary MOSFETs thereby allowing turn-on of the switch under zero voltage. In order to optimize the amount of reactive current required to achieve ZVS a variable frequency control scheme is implemented over the line cycle. Thus the amount of negative current in each switching cycle is dependent on the line cycle. Since the proposed topology operates with variable frequency, the conventional methods of modeling would not provide accurate small signal models for the inverter. A modified state-space approach taking into account the constraints associated with variable switching frequency as well as the negative current is used to obtain an accurate small signal model. Based on the linearized inverter model, a stable closed loop control scheme with peak current mode control is implemented for a wide range of operation. The system incorporates the controllers for both the positive as well as negative peak of inductor current. Simulation and the experimental results presented in the thesis confirm the viability of the proposed topology.

LINK: https://qspace.library.queensu.ca/bitstream/handle/1974/7317/Sukesh_Nikhil_201207_MASC.pdf?sequence=1&isAllowed=y

MICROINVERSOR FOTOVOLTAICO NÃO ISOLADO DE DOIS ESTÁGIOS-Gustavo Carlos Knabben-Programa de Pós-Graduação em Engenharia Elétrica da Universidade Federal de Santa Catarina

 

MICROINVERSOR FOTOVOLTAICO NÃO ISOLADO DE DOIS ESTÁGIOS 

AUTOR Gustavo Carlos Knabben  Dissertação submetida ao Programa de Pós-Graduação em Engenharia Elétrica da Universidade Federal de Santa Catarina para obtenção do Grau de Mestre em Engenharia Elétrica. 

Orientador: Prof. Denizar Cruz Martins, Dr.

 Co-orientador: Prof. Roberto Francisco Coelho, Dr. 

Florianópolis 2017

 RESUMO Esta dissertação de mestrado apresenta o procedimento utilizado no projeto e construção de um protótipo de microinversor fotovoltaico, capaz de processar energia de um módulo fotovoltaico de silício cristalino de até 250 W de potência e injetá-la na rede elétrica com 220 V de valor eficaz de tensão e 60 Hz de frequência. O trabalho compreende revisão bibliográfica em microinversores comerciais, normas para conexão à rede elétrica, caracterização de geradores fotovoltaicos, topologias aplicadas a microinversores e influência das correntes de modo comum na operação desses equipamentos. Optou-se por processar a energia em dois estágios de conversão. O primeiro, cccc, é composto por um conversor Boost com célula de ganho. O segundo, cc-ca, principal foco desta dissertação, é o conversor em ponte completa com modulação dois níveis. A estratégia de controle é baseada em compensação da corrente injetada na rede elétrica, com imposição, por PLL, de uma forma de onda senoidal em fase com a tensão; regulação do barramento cc principal; técnica de MPPT; método de antiilhamento; partida suave de todo o sistema; algoritmos de proteção; e desacoplamento dos estágios cc-cc e cc-ca por filtragem ativa. A experimentação do sistema projetado e construído contou com resultados satisfatórios e de acordo com teoria e simulação. 

Palavras-chave: Microinversor. Fotovoltaico. Rede Elétrica. Controle. Ponte Completa.

LINK:https://repositorio.ufsc.br/handle/123456789/178588

High-Performance Voltage Controller Design Based on Capacitor Current Control Model for Stand-alone Inverters Byeng-Joo Byen, Jung-Muk Choe and Gyu-Ha Choe--Dept. of Electrical Engineering, Konkuk University, Korea.

High-Performance Voltage Controller Design Based on Capacitor Current Control Model for Stand-alone Inverters Byeng-Joo Byen*, Jung-Muk Choe** and Gyu-Ha Choe†

 † Corresponding Author: Dept. of Electrical Engineering, Konkuk University, Korea. (ghchoe@konkuk.ac.kr) * Dept. of Electrical Engineering, konkuk University, Korea. (cooks321@konkuk.ac.kr) ** Dept. of Electrical Computer Engineering, Virginia Polytechnic Institute and State University, USA. (jmchoe@vt.edu) 

 Abstract – This study proposes high-performance voltage controller design that employs a capacitor current control model for single-phase stand-alone inverters. The single-phase stand-alone inverter is analyzed via modeling, which is then used to design the controller. A design methodology is proposed to maximize the bandwidth of the feedback controller. Subsequently, to compensate for the problems caused by the bandwidth limitations of the controller, an error transfer function that includes the feedback controller is derived, and the stability of the repetitive control scheme is evaluated using the error transfer function. The digital repetitive controller is then implemented. The simulation and experimental results show that the performance of the proposed controller is high in a 1.5 kW singlephase stand-alone inverter prototype. 

Keywords: AC-DC converter, Digital control, Repetitive control, Capacitor current control model

LINK: http://koreascience.or.kr/article/JAKO201525961704096.pdf

Estudo comparativo de estratégias de controle para inversores de fontes ininterruptas de energia-Dissertação de Mestrado-Autor Rodrigues, Álvaro Jorge -ESCOLA POLITÉCNICA DA UNIVERSIDADE DE SÃO PAULO

 Orientador Komatsu, Wilson (Catálogo USP) 

Banca examinadoraKomatsu, Wilson (Presidente) Kaiser, Walter Marafão, Fernando Pinhabel 

Resumo Em português

Este trabalho tem como objetivo reunir, registrar, estudar e comparar as estratégias de controle utilizadas em inversores para fontes ininterruptas de energia, efetuado através de levantamento bibliográfico, englobando estratégias antigas (implementadas muitas vezes na forma analógica) e recentes (com implementação digital). É realizada comparação dos desempenhos, determinados analiticamente por modelamento e/ou por simulação computacional, entre algumas estratégias de controle. É apresentado um método para a implementação digital de um inversor monofásico para fontes ininterruptas de energia com transformador na saída. O método utilizado consiste de: Análise e modelagem dos controladores e planta, adotando-se critérios para o ajuste dos respectivos parâmetros; Simulação no modo de tempo contínuo; Roteiro da discretização para possibilitar implementação digital; Simulação em tempo discreto; Implementação em protótipo experimental. O controle é realizado com uma estratégia de múltiplas malhas, usando três malhas: uma malha interna de corrente usando controlador proporcional com compensação feedforward da perturbação da tensão de saída no controle da corrente e uma malha externa de tensão com um controlador proporcional + ressonante. Uma terceira malha de controle externa a malha de tensão é adicionada para prevenir a saturação do núcleo do transformador. O inversor é implementado através de um arranjo físico de baixa potência, possibilitando comparação dos resultados de simulação e experimentais.

Título em inglês A comparative study of control strategies in inverters for uninterruptible power supplies.

Palavras-chave em inglêsPower electronics Protection of electrical devices Switch mode power supplies

LINK:https://teses.usp.br/teses/disponiveis/3/3143/tde-20012011-102638/pt-br.php