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The aim of this work is to develop a two-port black-box dc-dc converter modeling methodology for system level simulation and analysis. The models do not require any information about the components, structure, or control parameters of the converter. Instead, all the information needed to build the models is collected from unterminated experimental frequency response function (FRF) measurements performed at the converter power terminals. These transfer funtions are known as audiosuceptibility, back current gain, output impedance, and input admittance. The measurements are called unterminated because they do not contain any information about the source and/or the load dynamics. This work provides insights into how the source and the load affect FRF measurements and how to decouple those effects from the measurements. The actual linear time invariant model is obtained from the experimental FRFs via system identification. Because the the two-port model obtained from a set of FRFs is linear, it will be valid in a specific operating region defined by the converter operating conditions. Therefore, to satisfy the need for models valid in a wide operating region, a model structure that combines a family of linear two-port models is proposed. One structure, known as the Wiener structure, is especially useful when the converter nonlinearities are reflected mainly in the steady state currents and voltage values. The other structure is known as a polytopic structure, and it is able to capture nonlinearities that affect the transient and steady state converter behavior. The models are used for prediction of steady state and transient behavior of voltages and currents at the converter terminals. In addition, the models are useful for subsystem interaction and small signal stability assesment of interconnected dc distribution systems comprising commericially available converters. This work presents for first time simulation and stability analysis results of a system that combines dc-dc converters from two different manufucturers. All simulation results are compared against experimental results to verify the usefulness of the approach. / Ph. D.

The present dynamic manufacturing environment has been characterized by a greater variety of products, shorter life-cycles of products and rapid introduction of new technologies, etc. Recently, a new manufacturing paradigm, i.e. Reconfigurable Manufacturing Systems (RMS), has emerged to address such challenging issues. RMSs are able to adapt themselves to new business conditions timely and economically with a modular design of hardware/software system. Although a lot of research has been conducted in areas related to RMS, very few studies on system-level control for RMS have been reported in literature. However, the rigidity of current manufacturing systems is mainly from their monolithic design of control systems. Some new developments in Information Technology (IT) bring new opportunities to overcome the inflexibility that shadowed control systems for years. Component-based software development gains its popularity in 1990's. However, some well-known drawbacks, such as complexity and poor real-time features counteract its advantages in developing reconfigurable control system. New emerging Extensible Markup Language (XML) and Web Services, which are based on non-proprietary format, can eliminate the interoperability problems that traditional software technologies are incompetent to accomplish. Another new development in IT that affects the manufacturing sector is the advent of agent technology. The characteristics of agent-based systems include autonomous, cooperative, extendible nature that can be advantageous in different shop floor activities. This dissertation presents an innovative control architecture, entitled Component-based Intelligent Control Architecture (CICA), designed for system-level control of RMS. Software components and open-standard integration technologies together are able to provide a reconfigurable software structure, whereas agent-based paradigm can add the reconfigurability into the control logic of CICA. Since an agent-based system cannot guarantee the best global performance, agents in the reference architecture are used to be exception handlers. Some widely neglected problems associated with agent-based system such as communication load and local interest conflicts are also studied. The experimental results reveal the advantage of new agent-based decision making system over the existing methodologies. The proposed control system provides the reconfigurability that lacks in current manufacturing control systems. The CICA control architecture is promising to bring the flexibility in manufacturing systems based on experimental tests performed. / Ph. D.

Due to the increase in the integration of renewable energy to the grid, there is a critical need for varying the existing methods and techniques for grid operation. With increased renewable energy, mainly wind and photovoltaics, there is a reduction in inertia as the percentage of inverter-based resources is increasing. This can bring about an issue with the maintenance and operation of the grid with respect to frequency and voltage. Thus, the ability of inverters to regulate the voltage and frequency becomes significant. Under normal operation of the system, the ability of the inverters to support the grid frequency and voltage while following the grid is sufficient. However, the operation of the inverters during a resiliency mode, under which there is an extended outage of the utility system, will require the inverter functionality to go beyond support and actually maintain the voltage and frequency as done by synchronous machines, acting as the grid-forming inverter. This project focuses on the operation of grid forming sources based on the virtual synchronous generator to regulate the voltage and frequency in the absence of the grid voltage through decentralized control of the inverters in the distribution feeder. With the most recent interconnection standard for the distributed generation, IEEE-1547 2018, the inverter-based generation can be used for this purpose. The simulations are performed in the Simulink environment and the case studies are done on the IEEE 13 node test-feeder. / Master of Science / With the increase in the renewable energy sources in the present grid, the established methods for the operation of the grid needs to be updated due to the changes that the large amount of renewable energy sources bring to the system. Due to the While the conventional resources in the power system was mainly synchronous generators that had an inherent characteristic for frequency support and regulation due to the inertia this characteristic can be lacking in many of the renewable energy sources that are usually inverter-based. At present, the commonly adapted function for the inverters is to follow the grid which is suitable in case of normal operation of the power system. However, during emergency scenarios when the utility is disconnected and a part of the system has to operate independently the inverters need to be able to regulate both the voltage and frequency on their own. In this project the inverter-based control, termed as the virtual synchronous generator, has been studied such that it mimics the well-established controls for the conventional generators so that the inverter-based renewable resource appears similar to the conventional generator from the point of view of the grid in terms of the electrical quantities. The utilization of this type of control for operation of a part of the feeder with each inverter-based resource controlling its output in a decentralized manner is studied. The controls try to mimic the established controls for conventional synchronous machine and use it for maintain operation of the system with inverters.

As SystemC gains popularity as a System Level Design Language (SLDL) for System-On-Chip (SOC) designs, heterogeneous modelling and efficient simulation become increasingly important. The key in making an SLDL heterogeneous is the facility to express different Models Of Computation (MOC). Currently, all SystemC models employ a Discrete-Event simulation kernel making it difficult to express most MOCs without specific designer guidelines. This often makes it unnatural to express different MOCs in SystemC. For the simulation framework, this sometimes results in unnecessary delta cycles for models away from the Discrete-Event MOC, hindering the simulation performance of the model. Our goal is to extend SystemC's simulation framework to allow for better modelling expressiveness and efficiency for the Synchronous Data Flow (SDF) MOC. The SDF MOC follows a paradigm where the production and consumption rates of data by a function block are known a priori. These systems are common in Digital Signal Processing applications where relative sample rates are specified for every component. Knowledge of these rates enables the use of static scheduling. When compared to dynamic scheduling of SDF models, we experience a noticeable improvement in simulation efficiency. We implement an extension to the SystemC kernel that exploits such static scheduling for SDF models and propose designer style guidelines for modelers to use this extension. The modelling paradigm becomes more natural to SDF which results to better simulation efficiency. We will distribute our implementation to the SystemC community to demonstrate that SystemC can be a heterogeneous SLDL. / Master of Science

Recent research interests in studying the performance of different seismic force resisting systems (SFRS) have been shifting from component- (individual walls) to system-level (complete building) studies. Although there is wealth of knowledge on component-level performance of reinforced masonry shear walls (RMSW) under seismic loading, a gap still exists in understanding the response of these components within a complete system. Consequently, this study’s main objective is to investigate the influence of the diaphragm’s out-of-plane stiffness on the seismic response of RMSW buildings. In addition, the study aims to synthesize how this influence can be implemented in different seismic design approaches and assessment frameworks. To meet these objectives a two-story scaled asymmetrical RMSW building was tested under quasi-static cyclic loading. The analysis of the test results showed that the floor diaphragms’ out-of-plane stiffness played an important role in flexurally coupling the RMSW aligned along the loading direction with those walls orthogonal to it. This system-level aspect affected not only the different wall strength and displacement demands but also the failure mechanism sequence and the building twist response. The results of the study also showed that neglecting diaphragm flexural coupling influence on the RMSW at the system-level may result in unconservative designs and possibly undesirable failure modes. To address these findings, an analytical model was developed that can account for the aforementioned influences, in which, simplified load-displacement relationships were developed to predict RMSW component- and system-level responses under lateral seismic loads. This model is expected to give better predictions of the system response which can be implemented, within the model limitations, in forced- and displacement-based seismic design approaches. In addition, and in order to adapt to the increasing interest in more resilient buildings, this study presents an approach to calculate the system robustness based on the experimental data. Finally, literature shows that the vast majority of the loss models available for RMSW systems were based on individual component testing and/or engineering judgment. Consequently, this study proposes system damage states in lieu of component damage states in order to enhance the prediction capabilities of such models. The current dissertation highlights the significant influence of the diaphragm out-of-plane stiffness on the system-level response that may alter the RMSW response to seismic events; an issue that need to be addressed in design codes and standards. / Dissertation / Doctor of Philosophy (PhD)

<p>QC 20160428</p>

The goal of the work reported herein has been to model aspects of the electrical distribution system of an all-electric ship (AES) and to couple electrical load behavior with the thermal management network aboard the ship. The development of a thermally dependent electrical network has built upon an in-house thermal management simulation environment to replace the existing steady state heat loads with dynamic, thermally dependent, electrical heat loads. Quantifying the close relationship between thermal and electrical systems is of fundamental importance in a large, integrated system like the AES. This in-house thermal management environment, called the Dynamic Thermal Modeling and Simulation (DTMS) framework, provided the fundamental capabilities for modeling thermal systems and subsystems relevant to the AES. The motivation behind the initial work on DTMS was to understand the dynamics of thermal management aboard the ship. The first version, developed in 2007, captured the fundamental aspects of system-level thermal management while maintaining modularity and allowing for further development into other energy domains. The reconfigurable nature of the DTMS framework allowed for the expansion into the electrical domain with the creation of an electrical distribution network in support of thermal simulations. The dynamics of the electrical distribution system of the AES were captured using reconfigurable and physics-based circuit elements that allow for thermal feedback to affect the behavior of the system. Following the creation of the electrical network, subsystems and systems were created to simulate electrical distribution. Then, again using the modularity features of DTMS, a thermal resistive heat flow network was created to capture the transient behavior of heat flow from the electrical network to the existing thermal management framework. This network provides the intimate link between the thermal management framework and the electrical distribution system. Finally, the three frameworks (electrical, thermal resistive, and thermal management) were combined to quantify the impact that each system has relative to system-level operation. Simulations provide an indication of the unlimited configurations and potential design space a user of DTMS can explore to explore the design of an AES. / text

<p>Embedded computer systems are used as control systems in many products, such as VCRs, digital cameras, washing machines, automobiles, airplanes, etc. As the complexity of embedded applications grows and time-to-market of the products they are used in reduces, designing reliable systems satisfying multiple require-ments is a great challenge. Successful design, nowadays, cannot be performed without good design tools based on powerful design methodologies. These tools should explore different design alternatives to find the best one and do that at high abstraction levels to manage the complexity and reduce the design time.</p><p>A design is specified using models. Different models are used at different de-sign stages and abstraction levels. For example, the functionality of an application can be specified using hierarchical functional blocks. However, for such design tasks as mapping and scheduling, a lower-level flat model of interacting processes is needed. Deriving this model from a higher-level model of functional blocks is the main focus of this thesis. Our objective is to develop efficient strategies for such derivations, aiming at producing a process graph specification, which helps the synthesis tasks to find schedulable implementations. We proposed several strategies and evaluated them experimentally.</p>