Modeling and Analysis of PFC with Appreciable Voltage ripple to achieve Fast Transient Response

The design of an active Power Factor Corrector (PFC) leads to slow transient response in this type of converter. The reason for this  is due to  compensator placed in the output-voltage feedback loop is frequently designed to have narrow bandwidth to filter the voltage ripple of twice the line frequency obtaining from the PFC output voltage. This feedback loop is designed with this filtering effect because a relatively high ripple would cause considerable distortion in the reference line current feedback loop and line current. However, if the bandwidth of the compensator in the voltage loop is relatively wide, the transient response of the PFC range is improved. As a significance of the voltage ripple at the output of the compensator, both the static and the dynamic behaviors of the PFC change in comparison with no voltage ripple on the control signal. This paper presented, the static behavior of a PFC with appreciable voltage ripple in the output-voltage feedback loop using two parameters: the amplitude of the relative voltage ripple (k) on the control signal and its phase lag angle ( ).The total power processed by the PFC depends on these parameters, which do not vary with the load and which determine the Total Harmonic Distortion (THD) and the Power Factor (PF) at the input of the power factor correction converter. Finally, the results are verified by MATLAB/ Simulink simulation. Key words: Modeling, AC-DC boost converter, PFC controller, Power supplies

Design and Development of Sensorless Vector Control of Switched Reluctance Motor using Fuzzy Logic Controller

Switched reluctance motor (SRM) drive has gained popularity in high-performance motion control applications where high speeds and soft torque are required. Nevertheless, presence of flux harmonics in the air gap results in unattractive torque ripples. The torque ripples deteriorate the performance of the high-performance drive applications. In this paper the speed of the SRM drive is controlled by using sensorless vector control. Flux in the motor is estimated by an estimator and the switching of the inverter is modulated by the vector control. To reduce the ripples in the torque, fuzzy logic controller is used. Rule based fuzzy controller is developed by considering error and change in error as inputs. The proposed system is validated by changing the load of the drive. Results obtained are found be acceptable and torque ripples are minimized significantly

Design and Development of Sensorless Vector Control of Switched Reluctance Motor using Fuzzy Logic Controller

980-984Switched reluctance motor (SRM) drive has gained popularity in high-performance motion control applications where high speeds and soft torque are required. Nevertheless, presence of flux harmonics in the air gap results in unattractive torque ripples. The torque ripples deteriorate the performance of the high-performance drive applications. In this paper the speed of the SRM drive is controlled by using sensorless vector control. Flux in the motor is estimated by an estimator and the switching of the inverter is modulated by the vector control. To reduce the ripples in the torque, fuzzy logic controller is used. Rule based fuzzy controller is developed by considering error and change in error as inputs. The proposed system is validated by changing the load of the drive. Results obtained are found be acceptable and torque ripples are minimized significantly

MATLAB-Simulink environment based power quality improvement in photovoltaic system using multilevel inverter

Introduction. In this world of technical advancement, conventional resources are at the stage of destruction. To avoid such problems, we are going to use an alternative energy source namely solar by photovoltaic effect. The demand for multilevel inverters increased as they are used for different dynamic (high) voltage and dynamic (high) power appliances as they are capable of producing the output wave shape with low total harmonic distortion. Novelty. A new multilevel inverter is used in adding a (bidirectional) two way switch in between the capacitor and a traditional H-bridge module. This produces a better sine wave. By series connection of these two H-bridge modules, nine levels output voltage including zero is possible. The purpose of the proposed topology is reduction in the number of switches and it gives the good result with comparatively less power loss when it is compared with the other normal basic traditional inverters of the same output quality. Methods. In this paper, sinusoidal pulse width modulation technique is used for the working of the switches in the multilevel inverter. The results are verified by using simulation and also experimental setup is done. From the results it is observed that the proposed topology with reduced number of switches gives lower electromagnetic interference, lower harmonic distortion. Practical value. The total harmonic distortion value in the simulation is 14.4 % and practically it is 13.8 %.Вступ. У світі технічного прогресу звичайні ресурси перебувають у стадії руйнації. Щоб уникнути таких проблем, ми збираємося використати альтернативне джерело енергії, а саме сонячну енергію з фотоелектричним ефектом. Попит на багаторівневі інвертори збільшився, оскільки вони використовуються для різних динамічних (високих) напруг та динамічних (високих) потужностей, оскільки вони здатні формувати вихідну форму хвилі з низьким гармонічним загальним спотворенням. Новизна. Новий багаторівневий інвертор використовується для додавання двостороннього перемикача між конденсатором і традиційним модулем Н-моста. Це дає найкращу синусоїду. При послідовному з’єднанні двох модулів Н-моста можливо дев’ять рівнів вихідної напруги, включаючи нуль. Метою запропонованої топології є зменшення кількості перемикачів, що дає хороший результат при порівняно менших втратах потужності порівняно з іншими традиційними звичайними інверторами з такою ж вихідною якістю. Методи. У цій статті для роботи перемикачів у багаторівневому інверторі використовується метод широтно-імпульсної синусоїдальної модуляції. Результати перевіряються за допомогою моделювання, а також виконується експеримент. З результатів видно, що пропонована топологія зі зменшеною кількістю перемикачів дає менші електромагнітні перешкоди, менші гармонійні спотворення. Практична цінність. Сумарне значення гармонійних спотворень при моделюванні складає 14,4 %, а практично – 13,8 %

Increased levels of inflammatory cytokines in the female reproductive tract are associated with altered expression of proteases, mucosal barrier proteins, and an influx of HIV-susceptible target cells.

CAPRISA, 2016.Abstract available in pdf

Distinct genital tract HIV-specific antibody profiles associated with Tenofovir gel.

CAPRISA, 2016.Abstract available in PDF file

Genital inflammation undermines the effectiveness of tenofovir gel in preventing HIV acquisition in women.

CAPRISA, 2018.Abstract available in pdf

Goertzel Algorithm Based Islanding Detection Method Based on Small Second Order Harmonic Component for Grid Integrated PV Systems

782-787In modern power system many challenges have beenoccur when the distribution generation (DG) integrating to the power grid. One of the major challenges is islanding phenomena, which occurs when the power grid disconnected from the distribution system and disconnected power line still supplied by the DG system. This unintentional phenomenon must be detected to prevent the damage to equipment and hazardous effects to the workers. Active methods have small non-detection zone (NDZ). This paper proposes a new islanding detection method (IDM) based on injecting the harmonic component and monitoring the changes in power system by reducing the islanding detection time and zero crossing effect of the system. A new algorithm is introduced to detect islanding condition. The advantage of using Goertzel Algorithm (GA) is reducing the total number of computational effort.The proposed islanding detection method is small detection time compared to the other techniques.This paper simulate by using the MATLAB/SIMULINK

Design and Investigation of Adaptive Fixed Duty Cycle MPPT algorithm for Photovoltaic Systems

345-349As the usage of fossil fuel and generation has required the available resources, there was great boom for renewable energy sources. The most abundant solar energy is one of the most familiar sources of energy in the present world. In solar system, the photovoltaic array depends on the climatic variations, solar intensity and temperature of the atmosphere. The effect can be minimized. Though many MPPT techniques are described in the literature, sufficient comparative analysis with proper environmental condition is not addressed. In this paper, a novel Adaptive Fixed Step Size (AFDC) AFDC technique is designed and is evaluated that can adaptively adjusts to reference step size and hysteresis bandwidth, AFDC is also promises to result in improved efficiency with automatic self-tuning perturbations