Closed loop control of a cascaded multi-level converter to minimize harmonic distortion

As the United States Navy moves toward the all-electric ship, the need for a robust, high fidelity inverter for propulsion motors becomes mandatory. Military vessels require high power converters capable of producing nearly sinusoidal outputs to prevent torque pulsations and electrical noise that can compromise the mission location. This thesis presents a hybrid pulse-width-modulated controller for a 3x3 Cascaded Multi-Level Converter (CMLC). Ancillary results include a simple technique for extracting the reference sine wave from an independent bulk converter and implementing a synchronization technique that coordinates a space vector modulation controller with the switching pattern of a bulk inverter. The algorithms were tested on CMLC hardware that resides in the Naval Postgraduate School Power Systems Laboratory, and the results were compared with a sine-triangle pulse width modulation algorithm. The controller and converter were used to power a quarter-horsepower three-phase induction motor.http://archive.org/details/closedloopcontro109451913Approved for public release; distribution is unlimited

High-speed detection at two micrometres with monolithic silicon photodiodes

With continued steep growth in the volume of data transmitted over optical networks there is a widely recognized need for more sophisticated photonics technologies to forestall a ‘capacity crunch’[1]. A promising solution is to open new spectral regions at wavelengths near 2µm and to exploit the long-wavelength transmission and amplification capabilities of hollowcore photonic-bandgap fibres[2,3] and the recently available thulium-doped fibre amplifiers[4]. To date, photodetector devices for this window have largely relied on III-V materials[5] or, where the benefits of integration with silicon photonics are sought, GeSn alloys, which have been demonstrated thus far with only limited utility[6-9]. Here, we describe a silicon photodiode operating at 20 Gb/s in this wavelength region. The detector is compatible with standard silicon processing and is integrated directly with silicon-on-insulator waveguides, which suggests future utility in silicon-based mid-infrared integrated optics for applications in communications