Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Transient passive mode-locked ND:YAG laser using a semiconductor saturable absorber mirror(Montana State University - Bozeman, College of Letters & Science, 2022) Shaffer, Heather Rose; Chairperson, Graduate Committee: Joseph A. ShawQ-switched-mode-locking in a Nd:YAG bulk resonator was demonstrated using a semiconductor saturable absorber mirror (SESAM). A 10-W-pulsed-diode-pumped Nd:YAG laser system at Quantel USA by Lumibird, Inc. was adapted for mode-locking operation in a breadboard setup. Three SESAM mirrors were tested with initial reflectivities R 0=85%, 90%, and 95% in several cavity configurations to show enhanced sub-nanosecond pulse modulation at the free spectral range of each resonator. Transient Q-switched and long-pulse envelopes are shown with underlying mode-locked pulse modulation.Item Wide-area control strategies for improving transient stability in a multi-machine power systems(Montana State University - Bozeman, College of Engineering, 2020) Ojetola, Samuel Toluwanimi; Chairperson, Graduate Committee: Todd Kaiser and Josh WoldTransient stability is the ability of synchronous machines in an interconnected power system to remain in synchronism after been subjected to a large disturbance. Transient instability is one of the less probable but severe events that a power system encounter in its daily operations. Historically, it has been the dominant stability problem in power systems and has been the focus of much of the power industry's attention. Traditionally, when a generator or group of generators begin to lose synchronism with the rest of the system, they are tripped or islanded from the network to maintain transient stability and to prevent or limit cascaded outages. However, with the increase in the penetration of inverter-based generation, tripping schemes may become difficult to apply because of wide distribution of generation and loss of system inertia. This research presents control strategies that improves the transient stability of a power system without having to trip generators. This is achieved by modulating the active power absorbed or injected by distributed energy storage devices. These devices are located at the high voltage bus of several generators in a synchronous power system and are independently controlled. The strategy is based upon local and center-of-inertia frequency estimated in real time from wide-area measurements. It is shown that by absorbing or injecting real-power into a power system to remove as much kinetic energy gained during a disturbance as quickly as possible before it is converted to potential energy, synchronism can be maintained. The performance of the control strategy is evaluated on several multi-machine power system models. The result shows that this control strategy significantly improves the transient stability of power systems.Item Multi input minimax adaptive Antoulas-Anderson algorithm for rational approximation with stable poles(Montana State University - Bozeman, College of Letters & Science, 2021) Johns, William Richard; Chairperson, Graduate Committee: Lisa DavisThis thesis details the development of the 'symmetric stable multi-input multioutput Adaptive Antoulas Anderson' algorithm, we call this algorithm symmetric smiAAA. The symmetric smiAAA algorithm builds rational approximations, for multiple inputs. The approximations share a common set of parameters called the poles. The primary goal of this algorithm is to address shortcomings in multi-input multi-output rational approximation algorithms currently used in electro-magnetic transients programs. All state of the art algorithms currently follow a similar methodology: The user selects the number of poles to use and supplies an initial guess for their values. The algorithms optimize the shared poles and return the best approximation they found. The user is not guaranteed a specific accuracy in the approximations. If the results returned are not sufficiently accurate, the algorithm must be run again with additional poles. Symmetric smiAAA is designed with the goal of achieving user-defined accuracy, with no information about the number of poles. The user selects the desired accuracy of the approximations and the algorithm does the rest. Symmetric smiAAA returns approximations with the desired accuracy by finding the number of shared poles needed for the desired accuracy, and their values. This work introduces the following three features to the 'Adaptive Antoulas Anderson' algorithm. First, we extend the ideas from the single-input Adaptive Antoulas Anderson algorithm, to multi-input multi-output problems. Second, we introduce enforcement of constraints on the values of the poles. Lastly, we extend a single input post-processing optimization based upon the Lawson method, to multi-input multi-output problems. The symmetric smiAAA algorithm combines these three features with the symmetry enforcement introduced in the FastAAA algorithm. In order to test it against the current industry standards, we compare the symmetric smiAAA algorithm with Vector Fitting and the recently published RKFIT algorithms. These comparisons demonstrate that symmetric smiAAA produces approximations with similar accuracy and running time, while allowing the user to select only the desired accuracy. Symmetric smiAAA is a robust and powerful algorithm which provides the user full control over the final accuracy of the approximations.