40 research outputs found

    Power quality improvement utilizing photovoltaic generation connected to a weak grid

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    Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids and may have been considered as the culprit of poor power quality affecting other loads in particular sensitive loads connected to the same point of common coupling (PCC). This paper is intended to demystify the renewable generation, and turns the negative perception into positive revelation of the superiority of PV generation to the power quality improvement in a microgrid system. The main objective of this work is to develop a control method for the PV inverter so that the power quality at the PCC will be improved under various disturbances. The method is to control the reactive current based on utilizing the grid current to counteract the negative impact of the disturbances. The proposed control method is verified in PSIM platform. Promising results have been obtaine

    Analysis of Current Conveyor based Switched Capacitor Circuits for Application in ∆Σ Modulators

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    The reduction in supply voltage, loss of dynamic range and increased noise prevent the analog circuits from taking advantage of advanced technologies. Therefore the trend is to move all signal processing tasks to digital domain where advantages of technology scaling can be used. Due to this, there exists a need for data converters with large signal bandwidths, higher speeds and greater dynamic range to act as an interface between real world analog and digital signals. The Delta Sigma (∆Σ) modulator is a data converter that makes use of large sampling rates and noise shaping techniques to achieve high resolution in the band of interest. The modulator consists of analog integrators and comparators which create a modulated digital bit stream whose average represents the input value. Due to their simplicity, they are popular in narrow band receivers, medical and sensor applications. However Operational Amplifiers (Op-Amps) or Operational Transconductance Amplifiers (OTAs), which are commonly used in data converters, present a bottleneck. Due to low supply voltages, designers rely on folded cascode, multistage cascade and bulk driven topologies for their designs. Although the two stage or multistage cascade topologies offer good gain and bandwidth, they suffer from stability problems due to multiple stages and feedback requiring large compensation capacitors. Therefore other low voltage Switched-Capacitor (SC) circuit techniques were developed to overcome these problems, based on inverters, comparators and unity gain buffers. In this thesis we present an alternative approach to design of ∆Σ modulators using Second Generation Current Conveyors (CCIIs). The important feature of these modulators is the replacement of the traditional Op-Amp based SC integrators with CCII based SC integrators. The main design issues such as the effect of the non-idealities in the CCIIs are considered in the operation of SC circuits and solutions are proposed to cancel them. Design tradeoffs and guidelines for various components of the circuit are presented through analysis of existing and the proposed SC circuits. A two step adaptive calibration technique is presented which uses few additional components to measure the integrator input output characteristic and linearize it for providing optimum performance over a wide range of sampling frequencies while maintaining low power and area. The presented CCII integrator and calibration circuit are used in the design of a 4th order (2-2 cascade) ∆Σ modulator which has been fabricated in UMC 90nm/1V technology through Europractice. Experimental values for Signal to Noise+Distortion Ratio (SNDR), Dynamic Range (DR) and Figure Of Merit (FOM) show that the modulator can compete with state of art reconfigurable Discrete-Time (DT) architectures while using lower gain stages and less design complexity

    Advanced Modeling, Control, and Optimization Methods in Power Hybrid Systems - 2021

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    The climate changes that are becoming visible today are a challenge for the global research community. In this context, renewable energy sources, fuel cell systems and other energy generating sources must be optimally combined and connected to the grid system using advanced energy transaction methods. As this reprint presents the latest solutions in the implementation of fuel cell and renewable energy in mobile and stationary applications such as hybrid and microgrid power systems based on the Energy Internet, blockchain technology and smart contracts, we hope that they will be of interest to readers working in the related fields mentioned above

    The 1991 3rd NASA Symposium on VLSI Design

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    Papers from the symposium are presented from the following sessions: (1) featured presentations 1; (2) very large scale integration (VLSI) circuit design; (3) VLSI architecture 1; (4) featured presentations 2; (5) neural networks; (6) VLSI architectures 2; (7) featured presentations 3; (8) verification 1; (9) analog design; (10) verification 2; (11) design innovations 1; (12) asynchronous design; and (13) design innovations 2

    CMOS SPAD-based image sensor for single photon counting and time of flight imaging

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    The facility to capture the arrival of a single photon, is the fundamental limit to the detection of quantised electromagnetic radiation. An image sensor capable of capturing a picture with this ultimate optical and temporal precision is the pinnacle of photo-sensing. The creation of high spatial resolution, single photon sensitive, and time-resolved image sensors in complementary metal oxide semiconductor (CMOS) technology offers numerous benefits in a wide field of applications. These CMOS devices will be suitable to replace high sensitivity charge-coupled device (CCD) technology (electron-multiplied or electron bombarded) with significantly lower cost and comparable performance in low light or high speed scenarios. For example, with temporal resolution in the order of nano and picoseconds, detailed three-dimensional (3D) pictures can be formed by measuring the time of flight (TOF) of a light pulse. High frame rate imaging of single photons can yield new capabilities in super-resolution microscopy. Also, the imaging of quantum effects such as the entanglement of photons may be realised. The goal of this research project is the development of such an image sensor by exploiting single photon avalanche diodes (SPAD) in advanced imaging-specific 130nm front side illuminated (FSI) CMOS technology. SPADs have three key combined advantages over other imaging technologies: single photon sensitivity, picosecond temporal resolution and the facility to be integrated in standard CMOS technology. Analogue techniques are employed to create an efficient and compact imager that is scalable to mega-pixel arrays. A SPAD-based image sensor is described with 320 by 240 pixels at a pitch of 8μm and an optical efficiency or fill-factor of 26.8%. Each pixel comprises a SPAD with a hybrid analogue counting and memory circuit that makes novel use of a low-power charge transfer amplifier. Global shutter single photon counting images are captured. These exhibit photon shot noise limited statistics with unprecedented low input-referred noise at an equivalent of 0.06 electrons. The CMOS image sensor (CIS) trends of shrinking pixels, increasing array sizes, decreasing read noise, fast readout and oversampled image formation are projected towards the formation of binary single photon imagers or quanta image sensors (QIS). In a binary digital image capture mode, the image sensor offers a look-ahead to the properties and performance of future QISs with 20,000 binary frames per second readout with a bit error rate of 1.7 x 10-3. The bit density, or cumulative binary intensity, against exposure performance of this image sensor is in the shape of the famous Hurter and Driffield densitometry curves of photographic film. Oversampled time-gated binary image capture is demonstrated, capturing 3D TOF images with 3.8cm precision in a 60cm range

    Power Electronics in Renewable Energy Systems

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    Recent Advances in Wireless Communications and Networks

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    This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

    Data Acquisition Applications

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    Data acquisition systems have numerous applications. This book has a total of 13 chapters and is divided into three sections: Industrial applications, Medical applications and Scientific experiments. The chapters are written by experts from around the world, while the targeted audience for this book includes professionals who are designers or researchers in the field of data acquisition systems. Faculty members and graduate students could also benefit from the book
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