dq-based individual phase control of three-phase four-wire PWM rectifier for UPS Kim,SeungHo Dept. of Electrical Engineering Graduate School of Industry and Engineering Seoul National University of Science and Technology

ABSTRACT
dq-based individual phase control of three-phase four-wire PWM rectifier for UPS Kim,Seung Ho Dept. of Electrical Engineering Graduate School of Industry and Engineering Seoul National University of Science and Technology ABSTRACT Recently, the power quality sensitive loads such as computer and communications are so increased that the power supply with good power quality has come to the fore. However, it is possible that the public grid is interrupted by unexpected fault. Therefore, the UPS(uninterruptible power supply) has become an alternative solution to solve this problem. Generally, the UPS consist of a rectifier, a battery, and a PWM inverter and recently they use IGBT PWM rectifier to reduce input THDi and improve the input power factor. In this configurations the three-phase four-wire input UPS is widely used to eliminate the transformers in the UPS system. The aims of control algorithm for the IGBT PWM rectifier in three-phase four-wire UPS is a unity power factor. The SVM(space vector modulation) is one of the most popular and preferable PWM scheme because it reduces the commutation losses and harmonics in the output voltage, and has higher modulation index than SPWM(sinusoidal PWM) but they need a 3D SVM to control three-phase four-wire PWM rectifier and have some difficulties like as selection of inductance of input inductor and controls the neutral current. To improve this problem the another control algorithm which controls each phase individually has been suggested but this control algorithm use analog based control so ir's so sensitive and unstable. So another new algorithm which is added d-q control to control algorithm which controls each phase individually is suggested and it can control stably and can reduce neutral current too. This can be seen by computer simulation and experimental result.

Power Quality Improvement of Single-Phase Grid-Connected Photovoltaic Inverter - Trung-Kien Vu- Department of Information and Communications Engineering, Graduate School of Chungnam National University

A Dissertation for the Degree of Doctor of Philosophy
Power Quality Improvement of Single-Phase
Grid-Connected Photovoltaic Inverter
Department of Information and Communications Engineering
Graduate School
Chungnam National University
By
Trung-Kien

ABTRACT

The economical and environmental impacts of fossil fuels have forced society to investigate sustainable solutions. The interest has focused on the renewable energy sources since the green and clean benefits. Consequently, investments in research and development in the field of power electronics have increased proportionally, especially in high voltage and high power grid-connected systems. The distributed power generation (DG) systems are becoming more common as the need for electric power increases because of taking advantage of using different energy sources such as wind and solar. A few examples are hybrid cars, solar houses or hospitals in remote areas where providing clean, efficient and reliable electric power is critical to the loads. In such systems, the power is distributed from the source side to the load side via power electronic converters in the system. At low and medium power applications, the task is often left to single-phase inverters where they are the only interface between sources connected to dc bus and loads connected to an ac bus. This dissertation investigates the power quality improvements to properly regulate the power flow between renewable source and the utility network. The control method for single-phase inverters used in low and medium power DG systems is based on (and also takes the advantage of) the well-known d-q transformation (which is mostly employed for three-phase converters’ analysis and control design). The transformation requires at least two independent phases for each state variable in the system; thus a second phase must be created. This virtual-phase can be done by DSP implementation, hence there is no need for additional hardware in the system, making it more attractive and cost effective method. The Proportional-Resonant (PR) controller based current control scheme, compared with conventional Proportional-Integral (PI) controller, not only provides a superior transient response but also provides a zero steady-state error as well as a high disturbance rejection and a low output current THD under grid-tie mode operation. The entire controller can be implemented in a DSP digital control board which is becoming more common in power electronics converters within the past decade. Special attention is given to systems which demand a third-order LCL-filter as interface between inverter and grid. This filter configuration is widely employed in high power systems, in which the switching frequency is typically limited by the switching devices. The LCL-filter has the ability to reduce the level of harmonic distortion with less inductance, compared with the first-order L filter. On the other hand, it introduces undesirable characteristics, such as resonance, that must be compensated by the controller. Another issues related to the switching devices such as IGBT, MOSFET and others have very high switching frequency above tens of kilohertz. A blank-time is needed to avoid the conduction overlap of two switching devices in the same leg. This blank-time causes the phase error, output voltage distortions and fundamental voltage drop, which degrade the control performance and hence, may cause the power loss during generation process. Comparative analysis and design procedures of conventional PI and PR controller for current control technique have been presented. Furthermore, an output low-pass LCL-filter design procedure and a dead-time compensation method for a 3kW single-phase grid-connected full-bridge PV VSI have also been introduced in this study with the final results are implemented in a DSP TMS320F2812 based digital controller board.

Output Filter Design of Grid-Connected Inverter for High Power Offshore Wind Power System Kwangwoon graduate Department of Electrical Engineering Kim Dong

Abstract
Output Filter Design of Grid-Connected Inverter for High Power Offshore Wind Power System The output filter design for high power grid-connected inverter of offshore wind-turbine has many limitations such as low switching frequency, allowable DC-voltage, and the component volume and weight. In addition, the injected harmonic current into the grid is constrained by various grid connection requirements. This paper compared and weighed with several harmonic regulations and suggested the optimal design procedure of the output filter compliance with the grid code using spectrum analysis of inverter output voltage that contains harmonics. In this paper, the output filter of grid connected inverter for 7MVA offshore wind power system is designed to meet the BDEW harmonic currents limits and the IEEE 519-1992 requirements. The performance of the designed output filter is validated by extensive simulations using Matlab/Simulink.

Design of CLC Filter for Flyback Inverter of Grid-Connected Photovoltaic Systems Yesl Shin Electrical and Computer Engineering Graduate School Ajou University

Abstract
Yesl Shin
Electrical and Computer Engineering Graduate School Ajou University

This paper proposes a design of CLC filter which is the output filter of a flyback type current source inverter (CSI) for a photovoltaic system. This applied inverting system is micro-inverter, so the capacity and size of the entire system is critical factor for system evaluation. The proposed CLC filter consists of a conventional CL filter and an additional capacitor. The CLC filter guarantees the same or better performance about the reduction of current ripple than that of the CL filter. In such a case, the CLC filter is composed of the capacitor and the inductor with smaller capacity than the components of the CL filter. It can help the applied micro-inverter to be smaller size and cost less. For the advanced stability of output CL filters, the effect of passive damping methods for the CL filter is analyzed according to the resistive damping’s location. Among these damping methods, the one which has low power consumption is applied to the CLC filter and the effect of this method is also analyzed. A simulation and experiment are conducted to verify the performance of the proposed CLC filter and the validity of passive damping method.

SOLAR PHOTOVOLTAIC ENERGY GENERATION AND CONVERSION —FROM DEVICES TO GRID INTEGRATION by HUIYING ZHENG Department of Electrical & Computer Engineering in the Graduate School of The University of Alabama

SOLAR PHOTOVOLTAIC ENERGY GENERATION AND CONVERSION
FROM DEVICES TO GRID INTEGRATION
by
HUIYING ZHENG
A DISSERTATION
Submitted in partial fulfillment of the requirements
for the degree of Doctor of Philosophy
in the Department of Electrical & Computer Engineering
in the Graduate School of
The University of Alabama

LINK FULL THESIS

http://www.opal-rt.com/sites/default/files/technical_papers/SOLAR%20PHOTOVOLTAIC%20ENERGY%20GENERATION%20AND%20CONVERSION.pdf

Control Techniques for the Maximization of Power Converter Robustness and Efficiency in a Parallel Photovoltaic Architecture by David Charles Jones University of Colorado

Control Techniques for the Maximization of
Power Converter Robustness and Efficiency in
a Parallel Photovoltaic Architecture

by
David Charles Jones
B.S., Bradley University, 1985
M.S., University of Illinois, 1986
A thesis submitted to the
 Faculty of the Graduate School of the
University of Colorado in partial fulfillment
of the requirement for the degree of
Doctor of Philosophy
Department of Electrical Engineering-2013

FULL THESIS
http://media.proquest.com/media/pq/classic/doc/3003257911/fmt/ai/rep/NPDF?_s=sN5itq%2B4XsrpsD8SCePCM1vTBSw%3D

Harmonics in Large Offshore Wind Farms by Łukasz Hubert Kocewiak Faculty of Engineering, Science and Medicine at Aalborg University

ABSTRACT
The number of wind turbines with full converters in the MW range used in large offshore wind farms is rapidly increasing. They are connected through a widespread MV cable network with practicably no consumption and connected to the transmission system by long HV cables. This represents new challenges to the industry in relation to understanding the nature, propagation and effects of harmonics. Recently, the wind power sector is rapidly developing. This creates new challenges to the industry, and therefore more and more research projects, including harmonic analyses especially focused on wind power applications, are conducted and that is why the project was initiated and successfully developed.
LINK FULL THESIS
http://vbn.aau.dk/files/62660098/lukasz_kocewiak.pdf

Eletromagnetismo 01 - Curso de Graduação em Engenharia Eletrônica da UNIVERSIDADE FEDERAL PERNAMBUCO-BRASIL Prof. Eduardo Fontana -CURSO COMPLETO 18 VIDEOS

Eletromagnetismo 01 - Curso de Graduação em Engenharia Eletrônica da UNIVERSIDADE FEDERAL PERNAMBUCO-BRASIL Prof. Eduardo Fontana -CURSO COMPLETO 18 VIDEOS

http://www.ufpe.br/fontana/es203
Departamento de Eletrônica e Sistemas da UFPE 


2014.02 - Eletromagnetismo 1 - 6a. Edição

A1 - 18/09/2014	A2 - 22/09/2014	A3 - 25/09/2014
A4 - 06/10/2014	A5 - 09/10/2014	A6 - 13/10/2014
A7 - 16/10/2014	A8 - 27/10/2014	A9 - 30/10/2014
A10 - 10/11/2014	A11 - 13/11/2014	A12 - 17/11/2014
A13 - 27/11/2014	A14 - 01/12/2014	A15 - 01/12/2014
A16 - 15/12/2014	A17 - 18/12/2014	A18 - 19/01/2015

ADVANCED INVERTER CONTROL FOR UNINTERRUPTIBLE POWER SUPPLIES AND GRID-CONNECTED RENEWABLE ENERGY APPLICATIONS By Shuai Jiang Michigan State University

ADVANCED INVERTER CONTROL FOR UNINTERRUPTIBLE POWER

SUPPLIES AND GRID-CONNECTED RENEWABLE ENERGY

APPLICATIONS

By

Shuai Jiang

A DISSERTATION

Submitted to

Michigan State University

in partial fulfillment of the requirements

for the degree of

Electrical Engineering – Doctor of Philosophy

2013

ABSTRACT
ADVANCED INVERTER CONTROL FOR UNINTERRUPTIBLE POWER SUPPLIES AND GRID-CONNECTED RENEWABLE ENERGY APPLICATIONS By Shuai Jiang
The advancement of digital signal processors (DSPs) and programmable logic devices in modern power electronics systems offer great control flexibility and capability, providing attractive features particularly for applications in which complex control tasks are involved. This dissertation investigates some DSP based advanced control algorithms for pulse-width modulation (PWM) inverter applications, in particular, voltage regulated inverters connected with AC loads and current regulated inverters connected with utility grids. Uninterruptible power supply (UPS) is a typical example of voltage regulated inverter applications. It is widely used to supply high quality, continuous and disturbance-free AC power to critical loads such as medical equipments, computers and communication systems. A good UPS system requires not only excellent steady state performances in terms of voltage regulation and total harmonic distortions (THD) regardless of unknown load disturbances but also a fast transient response during load step change. In this dissertation, a three-phase four-wire AC-DC-AC double conversion UPS system is first studied. Multi-loop control strategies are designed to regulate the system input currents, DC voltages, and output voltages. Next, study will deep dive into a DC-AC three-phase UPS inverter. A high performance repetitive controller (RC) for the voltage regulated three-phase inverter is proposed. The proposed control algorithm can eliminate all the periodic distortions and guarantees a high quality sinusoidal output voltage under unknown and severely distorted loads. A novel 4th-order linear phase infinite-impulse-response (IIR) filter is first used in the RC such that harmonic distortions up to the 19th order are rejected. In order to achieve fast response during step load transient while still maintaining the low THD feature, a modified synchronousframe approach with significantly reduced delay is later proposed and investigated. Grid-connected inverters utilizing renewable energy sources (e.g., photovoltaic, wind, fuel cell, etc.) are growing rapidly in recent years along with the constantly growing global demand for electricity. A grid-connected inverter injects a synchronously regulated sinusoidal current to the utility grid with required low THD and high power factor. Using an LCL filter in such a system has been recognized as a small size low cost solution due to its -60dB/dec high frequency attenuation. In this dissertation, a high-resonance-frequency LCL filter with minimal size and cost requirement is designed. A proportional plus repetitive control hybrid strategy is then proposed to achieve very low THD current regulation and high power factor.
 FULL THESIS LINK:
http://etd.lib.msu.edu/islandora/object/etd%3A2193/datastream/OBJ/view

POWER CONVERTER SYSTEMS FOR HVDC TRANSMISSION INTEGRATED WITH WIND FARM Yeungnam University Department of Electrical Engineering AUTHOR Thanh Hai Nguyen

Ph.D. Thesis
POWER CONVERTER SYSTEMS FOR HVDC TRANSMISSION INTEGRATED WITH WIND FARM
 Advisor: Professor Dong-Choon Lee Presented as Ph.D. Thesis 2013 June Graduate School of Yeungnam University Department of Electrical Engineering Control and Electric Machinery ∙ Power Conversion Major
Author :Thanh Hai Nguyen

Abstract In this thesis, a novel power converter system for high-voltage direct current (HVDC) transmission integrating the offshore wind farm (WF) into the grid is proposed, in which a hybrid of a twelve-pulse diode rectifier (12P-DR) and a voltage-source converter (VSC) is employed. For this topology, the 12P-DR is capable of delivering a part of wind farm power, the rest of which is absorbed by the wind farm VSC (WFVSC) since the WFVSC is controlled and operated as a voltage source of a constant frequency. Also, the current at the PCC becomes almost sinusoidal since the WFVSC functions as an active power filter for the 11th- and 13th-order harmonic current components. By virtue of the diode rectifier, the voltage rating of the diode rectifier and the VSC is reduced by configuring them in series connection. Then, the cost and power loss of HVDC converters is reduced compared with the case of the conventional fully-rated VSC, whereas the performance is kept almost the same. By a simple VSC with two levels, the efficiency of the proposed HVDC converter is about 99.07% high, compared with 98.4% in the fully-rated VSC system, and the cost of power semiconductor devices including the gate drivers in the HVDC converter system is about 53.47% compared with that of in the VSC-based HVDC links. In addition, to improve the performance and the efficiency of the power converter system for HVDC links, the modular multilevel converter (MMC) is utilized instead of the simple 2-level VSC, in which the efficiency of the proposed HVDC system is about 99.27% compared with 99.0% and 98.4% of the HVDC transmission systems based on the fully-rated capacity of the MMC and the neutral-point clamped (NPC) multilevel converter, respectively. For integrating the HVDC transmission system with the distorted and unbalanced voltage of the network, a novel control scheme for the grid-side converter of the HVDC transmission systems based on a composite observer is proposed to mitigate the grid current distortions due to unbalanced and distorted grid voltage conditions for the gridconnected PWM converter. The composite observers can extract the fundamental and harmonic components of the grid voltages and currents precisely without any magnitude reduction or phase delay. Then, the positive- and negative-sequence components are separated from the fundamental components by all-pass filters. The grid current components are regulated by a multi-loop harmonic current controller, in which the positive-sequence component is regulated by PI (proportional-integral) controllers and the negative-sequence and harmonic components are regulated by PR controllers. This approach allows the unbalanced and distorted components in the grid current to be eliminated from the system. For the wind farm operation, a control strategy to smooth the output power of the wind farm before delivering to the grid is also proposed, in which the inertial effect of the wind turbines and coordinated operation of individual wind turbines (WT) are utilized. A two-level control scheme is applied to control the wind farm, which consists of a high-level control for the wind farm and low-level controls for individual WTs. The power references of the wind farm and each wind turbine generator are produced by the high-level controller, whereas the individual WTs are controlled to produce the power as their commands by the low-level controllers. With the control scheme, the output power of the WF is smoothened, even though the output powers of individual WTs are fluctuated. For this control strategy, when the reference power is lower than the available power, some of individual wind turbines are operated in the kinetic energy charge operation by increasing the turbine speeds. Then, some of individual wind turbines release the power by reducing the turbine speed, when the power command is higher than the available power. The PSCAD/EMTDC simulation results for a 500-MW HVDC transmission system integrating the wind farm into the grid have been shown to verify the validity of the proposed scheme. Also, the experimental tests have been carried out for the laboratoryscaled system of the HVDC link and wind turbine system.