Browsing by Subject "PWM"

Now showing 1 - 6 of 6
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    AVR PWM to I2C
    (2014-07-28) Murch, Austin
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    Data Conversion Techniques for Next Generation Communications
    (2017-12) Saha, Anindya
    The voice-only mobile-telephony 1G systems have evolved a long way to today’s data-driven 4G LTE networks, causing an exponential increase in mobile broadband data consumption. Furthermore, 5G is expected to deliver unprecedented data rates (tens of Gbps) exploiting mm-wave bands (30-300 GHz). Analog-to-digital converters (ADC) are one of the crucial factors in determining the pursued data rates. In the first part of this dissertation, a 100MS/s 9-bit companding SAR ADC, which exploits the statistical properties to reduce the PAPR of broadband multi-carrier signals in 4G LTE has been investigated. The architecture provides amplitude-specific gain with a fast instantaneous AGC, reducing the effects of PAPR and optimizing quantization noise, emulating the performance of a higher resolution ADC. Additionally, gain-before-sampling results in reduced sampling capacitor size, which lowers power and area. In the second part of this dissertation, a 1 GS/s 7-bit ADC using PWM technique and time-domain quantization is investigated to harness the benefits of the rapidly improving time resolution, so that the envisioned data rates in 5G can be realized with the lowest possible power. Thanks to digital delay line based time-domain computations, proposed architecture is highly digital therefore scalable, which is beneficial since scaling does not favor voltage-domain circuits.
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    Dynamic power flow control for a smart micro-grid by a power electronic transformer.
    (2011-05) Shah, Jalpa Kaushil
    A novel strategy, for control of the power flow for a smart micro-grid is proposed. The utility grid power is dynamically controlled by a Power Electronic Transformer (PET). A 60 Hz, step-down transformer is generally used at the point of common coupling (PCC), to connect the micro-grid to the power system grid. Substitution of the conventional 60Hz transformer, by a PET, results in enhanced micro-grid power management system, during grid-connected operation. The smart micro-grid is a set of controllable loads and distributed energy resources (DER); both renewable and non-renewable; that supply demand of a group of customers. The proposed dynamic power limiter (also referred to as PET) is a high-frequency, isolated power-converter system, comprised of a highfrequency step-down transformer and three-phase to single-phase matrix converters. The matrix converters are modulated with a novel pulse width modulation (PWM) strategy for a bi-directional power flow control. The output of the matrix converter generates a high frequency (few kHz) pulsating single phase AC at the primary and secondary of the transformer, which are phase shifted for active power control. The PET also allows voltage regulation by control of reactive power. The entire system; represented as two, three-phase AC systems with an intermediate high-frequency transformer; is simulated using Matlab/Simulink. The equivalent system has utility grid at the input side and a micro-grid on the output side. The micro-grid is modeled as an interconnected system consisting of set of DERs and smart loads. The simulation analyzes the change in micro grid’s power generation and consumption in response to the change in its local grid frequency, upon limiting the utility grid power. The PET hence restores the system frequency by adjusting supply and demand at the PCC. The micro-grid can now participate in frequency regulation for the main grid. The simulation results are obtained to verify the operation and claims of the dynamic power limiter as stated below: 1. Restricted active power flow to the micro-grid, at a desired value determined by the main utility grid. 2. Utilization of the change in local grid frequency, to dynamically control the active power generation or consumption within the micro-grid. 3. Decentralized control of the DERs as well as the controllable loads, which operate synchronously, to supply the demand within the micro-grid. 4. Bi-directional active-power flow capability at the PCC. 5. Voltage regulation by control of reactive power. 6. Contribution of the micro-grid components in frequency regulation of the main grid. 7. Smooth transition from islanding to grid-connected mode of the micro-grid, without the need of grid synchronization. 8. Extra degree of freedom due to the presence of active-power controller in a possible deregulation and market strategy within the micro-grid.
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    High Speed Rotary PWM On/Off Valves for Digital Control of Hydraulic Pumps and Motors
    (2014-08) Tu, Haink
    The research described in this dissertation focuses on the development of innovative on/off valves for high performance, high efficiency control of fixed displacement hydraulic pumps and motors. On/off valves, the hydro-mechanical equivalent of transistors, enable the application of digital control techniques found in electrical systems to hydraulics. These techniques, such as pulse-width-modulation (PWM), have the potential of combining the low cost, high bandwidth characteristics of valve control with the efficiency of variable displacement machines. Effective control of hydraulic systems using PWM requires that the on/off valve simultaneously exhibits fast switching speed, large flow area, and low actuation power. The valves developed in this dissertation exploit continuous rotary motion to achieve the desired, and traditionally competing, operating characteristics. A helical land is used to mechanically embed the desired PWM functionality into the valve spool. The rotary motion of the valve performs the switching functionality while its axial motion determines the PWM duty ratio. Several unique rotary valve concepts are presented in this dissertation for switched-mode pump and pump/motor circuits. An analysis framework is developed that predicts valve performance and typical losses which can be used for design and optimization. Physics based dynamic models of switched-mode pump and motor circuits are also developed for simulating system pressures and flow rates and for validating the analytical models. In addition, guidelines for sizing the valve sleeve based on fatigue considerations are formulated to aid prototype design. Prototype hardware is fabricated and extensively tested to validate the analysis, performance, and predicted efficiency of the proposed valves. The research in this dissertation verifies that helical land rotary valves used in switched-mode hydraulic circuits are capable of exceeding the efficiency of comparable metering valve circuits at moderate PWM frequencies. In two comparable systems, the switched-mode circuit achieved 84% efficiency at 50% output flow compared to 50% efficiency in the bleed off circuit. Analysis also shows that substantial gains in efficiency and switching frequency can be attained with improvements in valve configuration, circuit configuration, and valve geometry. Additional suggestions for further improving efficiency in switched-mode hydraulic systems are also discussed.
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    An investigation into pulse-width modulated AC electric drives with open-end winding machines
    (2013-01) Somani, Apurva
    Pulse-width modulated (PWM) ac drives have found numerous applications in industry and energy generation. Such drives offer advantages of higher efficiency and a wider range of operation as compared to line-connected machines. There are, however, certain disadvantages associated with PWM ac drives. These drives utilize bulky electrolytic capacitors in their power electronic sections which are costly. Also, the PWM inverter generates a switching common-mode voltage at the machine terminals. This causes spurious ground currents and harmful bearing currents through capacitively coupled paths to ground. Conventional ac machines used in electric drives are either star- or delta-connected and the machine has three terminals which are fed using a power electronic converter. In open-end winding machines, this star or delta connection is opened and the machine now has six terminals. These six terminals are then fed using two three-phase power converters. There are certain advantages to the open-end winding method, such as common-mode voltage reduction and increase in the voltage transfer ratio. Open-end winding ac drives have been investigated in this thesis. Different modulation strategies have been compared for the best performance in term of common-mode characteristics and output waveform quality. The inherent issue of circulating currents has been investigated and solutions have been proposed. Drive structures without dc-link capacitors have been proposed, analysed and their performance has been validated and evaluated.
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    Sensor Integration Software
    (2014-07-23) Murch, Austin