sábado, 28 de dezembro de 2013
SURFANDO NA WEB ENCONTREI ESTE LIVRO DE TRANSFORMADORES ELETRICOS NO SIGUENTE LINK :
sexta-feira, 27 de dezembro de 2013
segunda-feira, 23 de dezembro de 2013
A Book which deals exclusively with the theory and design of alternating current transformers is not likely to meet the requirements of a College text to the same extent as if its scope were broadened to include other types of electrical machinery. On the other hand, the fact that there may be a limited demand for it by college students taking advanced courses in electrical engineering has led the writer to follow the method of presentation which he has found successful in teaching electrical design to senior students in the school of Electrical Engineering at Purdue University. Stress is laid on the fundamental principles of electrical engineering, and an attempt is made to explain the reasons underlying all statements and formulas, even when this involves the introduction of additional material which might be omitted if the needs of the practical designer were alone to be considered.
Photovoltaic energy applications: state-of-the-art and perspectives Plenary Sessions BRASIL POWER ELECTRONICS CONFERENCE 2013
Photovoltaic energy applications: state-of-the-art and perspectives(Download Presentation)
Prof. Roberto Ziles, Ph.D.
University of São Paulo, Brazil
Oct. 31th, Thursday, 8:30 am - 10:00 am
The lecture devotes attention to the current situation of photovoltaic energy applications, discussing aspects such as the PV market characterization, technologies, costs and trends.
The lecture also describes the main configurations of photovoltaic systems and their integration into the national context, as well as major advances made in the country to provide the integration of distributed generation photovoltaic systems.
Roberto Zilles received his PhD in Telecommunications Engineering with specialty in Photovoltaic Systems from “Universidad Politecnica de Madrid” (1993) and the degree of “Livre Docência” with emphasis in renewable energy from São Paulo State University (2006). Currently, he is an Associate Professor and head of Scientific Division of Energy and Environment, Institute of São Paulo State University. Dr. Zilles is an Editorial Board member of “Progress in Photovoltaics: Research and Applications” journal, head of Brazilian Photovoltaic Energy Association, and vice head of Amazon National Institute of Science and Renewable Energy Technologies.
domingo, 22 de dezembro de 2013
sábado, 21 de dezembro de 2013
A New Three-Phase Parallel Active Power Filter
with Outages and PCC Voltage Compensation
Under the supervision of
Prof. DONG-SEOK HYUN, Ph.D.
Dept. of Electrical Engineering
The Graduate School of Hangyang University
This paper is a research on a new three-phase parallel active
power filter with outages and PCC voltage compensation under the
utility problems caused by the proliferation of non-linear loads such
as harmonics, increment of reactive power, voltage variation, and
blackouts. For these purposes, this paper presents (i) the optimal
design of parallel active power filter (ii) the modified PWM
modulation strategy which can operate the power conversion
system by using the single current sensor (iii) the detection method
of negative sequence and control scheme under the unbalanced load
condition (iv) the control method of constant PCC voltage (v) UPS
control method caused by blackouts in typical distribution systems
and the relations of each scheme.
In a design method of the parallel active filter, an analytic model
on active filter is proposed. For this purpose, control circuit, power
circuit, IGBT drive, and design method of the passive filter are
proposed. In a modified PWM modulation strategy, a technique for
reconstructing converter line currents using the information from a
single current sensor in the DC-link of a converter and comparative
evaluation of the performance of single sensor control techniques in
the DC-link for voltage-source PWM converters is presented. And
when 3f input currents cannot be reconstructed, three methods to
acquire the DC-link current are also proposed.
Design of Advanced Voltage Controller for
Three-Phase UPS inverters
Under the supervision of
Prof. DONG-SEOK HYUN, Ph.D.
Dept. of Electrical Engineering
The Graduate School of Hanyang University
Inverter system, which uses LC component as the output filter, is essential for a UPS (Uninterruptible Power supply), UPQC (Universal Custom Power Conditioner) and PCS (Power Conditioning System) for the photovoltaic power system. This paper presents DSP (Digital Signal Processor) controlled voltage controller for a 3-phase UPS inverter, which is able to compensate the voltage distortions due to unbalanced and nonlinear loads. The paper discussed the problem of conventional control schemes for the compensation of voltage distortion when they are applied to UPS inverter, and proposes advanced synchronous reference frame control scheme which is able to overcome the problem. In order to solve the problem of low damping ratio of LC filter, the inverter current feed-forward compensator including the selection of the feed-forward gain is proposed. And the digital filter for a compensation of the voltage distortion due to unbalanced and nonlinear loads is also proposed, which makes PI controllers in the synchronous reference frame are able to operate with DC values even under nonlinear and unbalanced load, likewise ensures PI controllers are able to provide zero steady state error. In order to improve the practical usability of the proposed scheme in the paper, the realization of the PLL and the parallel operation, which are essential for UPS, using the proposed controller is also presented. Especially, this paper shows that the feed-forward compensation of the inverter current and the PWM synchronization method proposed in the paper ensures a high precise load-sharing performance in parallel operation of inverter system. The effectiveness of the proposed scheme has been investigated and verified in digital simulation. This thesis also investigates the digital implementation of the proposed systems and all of the related theoretical concepts and control systems have been verified in experimental prototype of the UPS systems.
sexta-feira, 20 de dezembro de 2013
3 Replacing a junior electrician cross arm on 10KV line and tie on a porcelain line (power) 4 with a digital multimeter to determine power transistor using a digital multimeter pin 5 to determine the three small power transistor 6 pin electrical degrees
quinta-feira, 19 de dezembro de 2013
CHINA ATERIZOU COM SUCESSO SUA PRIMEIRA SONDA ESPACIAL NÃO TRIPULADA NA LUA,CHINA E APENAS O TERCEIRO PAIS A POUSAR NA LUA,SEGUINDO OS EUA E A ANTIGA UNIÃO SOVIETICA,QUE TANTO REALIZOU AS TAREFAS DECADAS ATRAS. "E UMA CONQUISTA DIGNA DE RESPEITO",DISSE JOHN LOGSDON,PROFESSOR EMERITO DA UNIVERSIDADE DE GEORGE WASHINGTON,QUE HA MUITO TEM MONITORADO POLITICA ESPACIAL.
'CHANG-3 E IMPRESSIONANTE COMO O PRIMEIRO POSSO NA LUA EM QUASE QUATRO DECADAS,CAINDO EM UM LUGAR QUE NÃO FOI EXPLORADO E USANDO INSTRUMENTAÇÃO CIENTIFICA RELATIVAMENTE AVANÇADA.
terça-feira, 17 de dezembro de 2013
Analysis of the Internal Electrical Characteristics of Electronic Power Transformers Yang Yi*, Cheng-Xiong Mao*, Dan Wang†, and Ji-Ming Lu**
Abstract The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC–DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC–DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations,and experiments confirm the theoretical analysis of the subunit of EPT.
New Isolated Single-Phase AC-DC Converter for Universal Input Voltage Ming-Rong Lee*, Lung-Sheng Yang†, and Chia-Ching Lin*
Modeling and Control Method for High-power Electromagnetic Transmitter Power Supplies Fei Yu† and Yi-ming Zhang*
Modeling and Control Method for High-power Electromagnetic Transmitter Power Supplies Fei Yu† and Yi-ming Zhang* †*College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing, China
Study on the Influence of Distribution Lines to Parallel Inverter Systems Adopting the Droop Control Method Xuan Zhang*, Jinjun Liu*, Zhiyuan You†, and Ting Liu*
Study on the Influence of Distribution Lines to Parallel Inverter Systems Adopting the Droop Control Method Xuan Zhang*, Jinjun Liu*, Zhiyuan You†, and Ting Liu* *†Dept. of Electronic Engineering, Xi’an Jiaotong University, Xi'an, China Abstract This paper takes into account the influence of the different impedances of distribution lines on power distribution among inverters when the inverters are paralleled with the droop control method. The impact of distribution lines on the power distribution of inverters can be divided into two aspects. Firstly, since the distributed generators are in low voltage grids, there is resistive impedance in the distribution lines, which will cause control coupling and reduce system stability. The virtual negative resistive impedance of inverters is adopted in this paper to neutralize the resistive element of distribution lines and thus make the distribution line impedance purely inductive. Secondly, after solving the resistive impedance problem, the difference in the inductive impedance value of distribution lines due to the low density of distributed generators will cause an unequal share of reactive power. With regards to this problem, modification is put forward for the droop control strategy to share the reactive power equally. The feasibility of the design is validated by simulation and experimental results.
Control Method for Reducing the THD of Grid Current of Three-Phase Grid-Connected Inverters Under Distorted Grid Voltages
Control Method for Reducing the THD of Grid Current of Three-Phase Grid-Connected Inverters Under Distorted Grid Voltages Thanh-Vu Tran*, Tae-Won Chun†, Hong-Hee Lee*, Heung-Geun Kim**, and Eui-Cheol Nho*** *†Dept. of Electrical Engineering, University of Ulsan, Ulsan, Korea **Dept. Of Electrical Engineering, Kyungpook National University, Daegu, Korea ***Dept. of Electrical Engineering, Pukyong National University, Busan, Korea
Abstract This paper proposes a control method for reducing the total harmonic distortion (THD) of the grid current of three-phase grid-connected inverter systems when the grid voltage is distorted. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for the minimum point of the THD. Both the gain and angle of the compensation voltage at the minimum point of the THD of the grid current are derived with the variation of cut-off frequencies of the hardware LPF. Simulation and experimental results show the validity of the proposed control methods.
The Effect of Transformer Leakage Inductance on the Steady State Performance of Push-pull based Converter with Continuous Current Qian Chen†, Trillion Q. Zheng*, Yan Li*, and Tiancong Shao*
The Effect of Transformer Leakage Inductance on the Steady State Performance of Push-pull based Converter with Continuous Current Qian Chen†, Trillion Q. Zheng*, Yan Li*, and Tiancong Shao* †*School of Electrical and Engineering, Beijing Jiaotong University, Beijing, China Abstract As a result of the advantages such as high efficiency, continuous current and high stability margin, push-pull converter with continuous current (PPCWCC) is competitive for battery discharge regulator (BDR) which plays an important role in power conditioning unit (PCU).Leakage inductance yields current spike in low-ripple current of PPCWCCs. The operating modes are added due to leakage inductance. Therefore the steady state performance is affected, which is embodied in the spike of low-ripple current. PPCWCCs which are suitable for BDR can be separated into three types by current spike characteristics. Three representative topologies IIs1, IIcb2 and Is3 are analyzed in order to investigate the factors on the magnitude and duration of spike. Equivalent current sampling method (ECSM) which eliminates the sampling time delay and achieves excellent dynamic performance is adopted to prevent the spike disturbance on current sampling. However, ECSM reduces the sampling accuracy and telemetry accuracy due to neglecting the spike. In this paper, ECSM used in PPCWCCs is summarized. The current sampling error is analyzed in quality and quantity, which provides the foundation for offsetting and enhancing the telemetry accuracy. Finally, current sampling error rate of three topologies is compared by experiment results, which verify the theoretical analysis.
Design of an LCL-Filter for Three-Parallel Operation of Power Converters in Wind Turbines Hae-Gwang Jeong*, Dong-Keun Yoon**, and Kyo-Beum Lee†
of Power Converters in Wind Turbines
Hae-Gwang Jeong*, Dong-Keun Yoon**, and Kyo-Beum Lee†
†*Department of Electrical and Computer Engineering, Ajou University, Suwon, Korea
**Research Group, LG Innotek Co., Ltd., Ansan, Korea
This paper proposes a design scheme for an LCL-filter used for the three-parallel operation of the power converters in high-capacity wind turbines. The designs of the power devices and grid connected filter are difficult due to the high level voltages and currents in huge-capacity wind turbines. To solve these problem, this paper presents three-parallel operation and LCL-filter design techniques optimized by parallel operation. Furthermore, the design of an inverter side inductance of the LCL-filter is discussed in detail considering the switching modulation method. Simulation and experimental results demonstrate the validity of the designed filter and wind turbines.
segunda-feira, 16 de dezembro de 2013
Parallel Operation of Three-Phase Four wire UPS using Droop Control ( Hyunseob Kim․Jungho Han․Joong-Ho Song )
* Main author：Dept. of Railway Electrical and
Signaling Engineering, Seoul National
University of Science and Technology,
Candidate of MS
** Corresponding author：Dept. of Electrical and
Information Engineering, Seoul National
University of Science and Technology,
A new droop control method which can be applied to 3-phase 4-wire uninterruptible power supply is
proposed in this paper. The droop control method for parallel operation is very attractive one as UPS
parallel operation can be carried out without any data communication devices provided among UPS
systems connected, but it reportedly shows a PnP(plug-and-play) problem. A basic reason why a
circulating current could flow among parallel-connected UPS systems is clearly investigated as well
when droop-controlled-ups systems are operated in the manner of PnP. The proposed algorithm is
deduced from the investigated result and is basically structured to keep a balanced frequency and
balanced voltage profile against power variation. This paper shows that balanced parallel operation of
droop control method can be obtained under unbalanced load as well as balanced load conditions .when PnP operation is needed and load change occurs.
Power Factor Correction of Single-phase Boost Converter for Low-cost Type UPS Configuration Jong-Chan Park․Jin-Geun Shon
Power Factor Correction of Single-phase Boost Converter for Low-cost Type UPS Configuration 박 종 찬*․손 진 근† (Jong-Chan Park․Jin-Geun Shon) The Transactions of the Korean Institute of Electrical Engineers Vol. 62P, No. 3, pp. 145～150, 2013
Abstract -A novel AC to DC PWM converters with unity input power factor are proposed to overcome the above shortcoming. The main function of these converters is to shape the input line current to force it exactly in phase with the input AC voltage. Therefore, the input power factor can be improved to near unity and the input current harmonics can be eliminated. In this paper, half-bridge converter with two active switches and two diodes are utilized for low-cost type UPS configuration. By having only two semiconductors in the current path at any time, losses can be reduced over the conventional boost topology. Also, this converter provides controllable dc-link voltage, high power factor, and low cost type converter by simple power circuits. Simulation results show that the proposed half-bridge converter/inverter control technique can be applied to single-phase low-cost type UPS systems successfully.
LLC Resonant Converter design for Uninterruptible Power Supply Battery
Kwang-Min Yoo1, Seung-Joo Kim1, Kyoung-Dong Kim1, Seung-Hee Park1, Yong-Seop Byeon,
Seung-Beom Lim, and Jun-Young Lee
Kwang-Min Yoo1, Seung-Joo Kim1, Kyoung-Dong Kim1, Seung-Hee Park1, Yong-Seop Byeon,
Seung-Beom Lim, and Jun-Young Lee
A Controller Design for a Stability Improvement of an On-Board Battery Charger Hae-Gwang Jeong* and Kyo-Beum Lee†
Hae-Gwang Jeong* and Kyo-Beum Lee†
Corresponding Author: Department of Electrical and Computer
Engineering, Ajou University, Suwon, Korea. (email@example.com)
* Dept. of Electrical and Computer Engineering, Ajou University,
Suwon, Korea. (firstname.lastname@example.org)
Received: May 27, 2013; Accepted: June 7, 2013
Abstract – This paper proposes the controller design for a stability improvement of an on-board
battery charger. The system is comprised of a power factor correction (PFC) circuit and phase shift
full-bridge DC-DC converter. The PFC circuit performs the control of the DC-link voltage and the
input power factor. The DC-DC converter regulates the voltage and the current in the battery using the
DC-link voltage. This paper proposes the design method of PI controller for the PFC circuit using a
small signal model. The analysis and design of a type-three controller for the DC-DC converter is also
presented. A simulation and experiment has been performed on the on-board battery charger and their
results are presented to verify the validity of the proposed system.
A Three-Phase High Frequency Semi-Controlled Battery Charging Power Converter for Plug-In Hybrid Electric Vehicles
Battery Charging Power Converter for Plug-In
Hybrid Electric Vehicles
Mahmoud M. Amin and Osama A. Mohammed†
† Dept. of Electrical and Computer Eng., Florida International University, Florida, United States
This paper presents a novel analysis, design, and implementation of a battery charging three-phase high frequency semicontrolled
power converter feasible for plug-in hybrid electric vehicles. The main advantages of the proposed topology include
high efficiency; due to lower power losses and reduced number of switching elements, high output power density realization, and
reduced passive component ratings proportionally to the frequency. Additional advantages also include grid economic utilization
by insuring unity power factor operation under different possible conditions and robustness since short-circuit through a leg is not
possible. A high but acceptable total harmonic distortion of the generator currents is introduced in the proposed topology which
can be viewed as a minor disadvantage when compared to traditional boost rectifiers. A hysteresis control algorithm is proposed
to achieve lower current harmonic distortion for the rectifier operation. The rectifier topology concept, the principle of operation,
and control scheme are presented. Additionally, a dc-dc converter is also employed in the rectifier-battery connection. Test results
on 50-kHz power converter system are presented and discussed to confirm the effectiveness of the proposed topology for PHEV
A Study on the Hot Spot Temperature in 154kV Power Transformers Dong-Jin Kweon†, Kyo-Sun Koo*, Jung-Wook Woo* and Joo-Sik Kwak*
Dong-Jin Kweon†, Kyo-Sun Koo*, Jung-Wook Woo* and Joo-Sik Kwak*
Abstract – The life of a power transformer is dependent on the life of the cellulose paper, which
influenced by the hot spot temperature. Thus, the determination of the cellulose paper’s life requires
identifying the hot spot temperature of the transformer. Currently, however, the power transformer
uses a heat run test is used in the factory test to measure top liquid temperature rise and average
winding temperature rise, which is specified in its specification. The hot spot temperature is calculated
by the winding resistance detected during the heat run test. This paper measures the hot spot
temperature in the single-phase, 154kV, 15/20MVA power transformer by the optical fiber sensors and
compares the value with the hot spot temperature calculated by the conventional heat run test in the
factory test. To measure the hot spot temperature, ten optical fiber sensors were installed on both the
high and low voltage winding; and the temperature distribution during the heat run test, three
thermocouples were installed. The hot spot temperature shown in the heat run test was 92.6℃ on the
low voltage winding. However, the hot spot temperature as measured by the optical fiber sensor
appeared between turn 2 and turn 3 on the upper side of the low voltage winding, recording 105.9℃.
The hot spot temperature of the low voltage winding as measured by the optical fiber sensor was 13.3℃
higher than the hot spot temperature calculated by the heat run test. Therefore, the hot spot factor (H)
in IEC 60076-2 appeared to be 2.0.
Implementation of a High Efficiency Grid-Tied Multi-Level Photovoltaic Power Conditioning System Using Phase Shifted H-Bridge Modules
Multi-Level Photovoltaic Power Conditioning
System Using Phase Shifted H-Bridge Modules
Jong-Pil Lee†, Byung-Duk Min**, and Dong-Wook Yoo*
†*Power Conversion Research Center, Korea Electrotechnology Research Institute, Changwon, Korea
**Green Power Co. Ltd, Suwon, Korea
This paper proposes a high efficiency three-phase cascaded phase shifted H-bridge multi-level inverter without DC/DC
converters for grid-tied multi string photovoltaic (PV) applications. The cascaded H-bridge topology is suitable for PV
applications since each PV module can act as a separate DC source for each cascaded H-bridge module. The proposed phase
shifted H-bridge multi-level topology offers advantages such as operation at a lower switching frequency and a lower current
ripple when compared to conventional two level topologies. It is also shown that low ripple sinusoidal current waveforms are
generated with a unity power factor. The control algorithm permits the independent control of each DC link voltage with a
maximum power point for each string of PV modules. The use of the controller area network (CAN) communication protocol for
H-bridge multi-level inverters, along with localized PWM generation and PV voltage regulation are implemented. It is also
shown that the expansion and modularization capabilities of the H-bridge modules are improved since the individual inverter
modules operate more independently. The proposed topology is implemented for a three phase 240kW multi-level PV power
conditioning system (PCS) which has 40kW H-bridge modules. The experimental results show that the proposed topology has good performance.
domingo, 15 de dezembro de 2013
E.-H. Kim J.-M. Kwon B.-H. Kwon
Department of Electronic and Electrical Engineering, Pohang University of Science and Tech, Republic of Korea
Abstract: A transformerless three-phase on-line uninterruptible power supply (UPS) is proposed. The proposed
UPS is composed of a rectifier, an inverter and a battery charger/discharger. The rectifier regulates a DC-link
voltage and performs power factor correction. On the other hand, the inverter provides a regulated sinusoidal
output voltage and has the current-limiting capability for an impulsive load. The battery charger/discharger
reduces the number of battery and supplies the power demanded by the load in the event of the input
power failure or abrupt decrease of the input voltage. Since both neutral lines of the input and output
voltages are connected at the centre of the DC-link, the need for an isolation transformer is eliminated and
the size, weight and cost of the system are significantly reduced. Additionally, new control algorithms of the rectifier, the charger/discharger and the inverter are proposed.
In this thesis, electronic ballast with power factor correction for high intensity discharging (HID) lamp is presented. The proposed topology is a two-stages circuit that requires only one switch and one inductor for each stage. Power factor correction (PFC) stage is boost dc-to-dc converter operating in continuous conduction mode (CCM) to achieve low total harmonic distortion (THD) and proper output characteristics over a wide range of load (10% ~ 90% full load).
This control implementation for against broken lamp can be easily implemented with the proposed circuitry. The high-frequency supply the lamp is given by the flyback converter. Input AC voltages ranges from 90V~260V are allowable for our system with a low DC bus voltage below 450V. It is suitable for electronic ballast with medium power HID lamp. The topologies could work under the circumstance of two 250W fluorescent lamps at 66 KHz switching frequency.
A STUDY OF CHARGING EQUALIZATION AND DISCHARGING POWER MANAGEMENT FOR SERIES AND PARALLEL CONNECTED BATTERY PACK
AND DISCHARGING POWER MANAGEMENT FOR SERIES AND
PARALLEL CONNECTED BATTERY PACK
研 究 生： 蔡志明 Jr-Ming Tsai
指導教授： 李清元教授 Prof. Ching-Yuan Lee
Master Thesis Department of Electrical Engineering Tatung University
The object of this paper is to research the methodology of charging equalization and
discharging power management of the series and paralleled connected battery sets under the
considerations of the safety, economics and practicality to improve the overall battery sets
efficiency. The battery management system used the isolation method to ensure the charging
equalization of batteries; and to protect from the abnormal situation during discharging of the
series-connected battery sets. As for the parallel-connected battery sets, this paper proposes
a multi-mode chopper. It will enable to control and distribute the output current from each
The serial and parallel connection scheme uses two batteries as the smallest unit. The number of batteries may be expanded at will. The system performs the charging and discharging tests of the serial and parallel connected GS LC18650 1800mAh lithium battery sets. Finally, a single-chip microprocessor, PIC16F877 is use to implement the control method of the proposed system. Via the experimentation, it proofs that the methods can performs its feasibility and good characteristics as anticipated.
LINK FULL THESIS
sexta-feira, 13 de dezembro de 2013
domingo, 8 de dezembro de 2013
segunda-feira, 2 de dezembro de 2013
domingo, 1 de dezembro de 2013
AVALIAÇÃO DAS INSTALAÇÕES ELÉTRICAS DE CENTRO CIRÚRGICO. ESTUDO DE CASO: HOSPITAL UNIVERSITÁRIO DA UFMS.
UNIVERSIDADE FEDERAL DE MATO GROSSO DO SUL
PROGRAMA DE PÓS-GRADUAÇÃO EM ENGENHARIA
AVALIAÇÃO DAS INSTALAÇÕES ELÉTRICAS DE
ESTUDO DE CASO: HOSPITAL UNIVERSITÁRIO
Dissertação submetida à
Universidade Federal de Mato Grosso do Sul
como parte dos requisitos para a
obtenção do grau de Mestre em Engenharia Elétrica
JOÃO CESAR OKUMOTO
http://repositorio.cbc.ufms.br:8080/jspui/bitstream/123456789/646/1/João Cesar Okumoto.pdf