Browsing by Subject "Time Scales"

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    Analysis and Synthesis of Smart Wires in an Electric Power System
    (2018-12) Bekkala, Allan
    When electric current overloading on the power system occurs, utilities often rely on traditional methods such as line upgrades or other system improvements for mitigation. Traditional methods often require major capital investment, multi-year lead times, and a fixed project scope. Operating conditions can often change with less than a year notice, particularly in today’s current regulatory environment. Smart Wires offers a flexible approach to mitigate line overload conditions and congestion by means of changing the reactive impedance, granting the ability to transform the energy grid into a dynamically controlled system better positioned to deal with intermittent resources. This thesis addresses a problem shown in a power flow study that reveals overload conditions due to changes in power generation. This research presents a Smart Wires solution as an effective means to mitigate the overload conditions. Smart Wires offers three products: PowerLine Guardian, Power Guardian, and Smart Valve. The Smart Valve is the best option as a solution for the problem statement when considering weight and number of devices. In order to ensure successful implementation of this technology, it needs to be tested and simulated properly. Automation is used in order to determine how many power flow control devices are needed and to consider the longevity of the solution. Longevity is primarily influenced by load growth, and graphical evidence is given for a solution lasting up to 20 years. This thesis addresses the challenges that can arise from a transmission line whose reactive impedance varies depending on settings. Finally, the problem of time scale analysis and synthesis of the transmission line, with and without Smart Wires, is addressed.
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    Decouple and Control Strategy for Variable Speed Variable Pitch Wind Energy Conversion System
    (2018-03) Modugula, Shanmukha Reddy
    With the rapid growth of wind energy usage, the complexity of control systems used in the wind energy conversion systems (WECS) is also growing. As the nature of the wind is indeterminate, control systems must be able to deal with the stochastic nature of the wind and must be able to give the desired results. Thus, consideration of different types of advanced controllers for the WECS becomes important. One of the promising divide (decouple) and conquer (control) strategy using singular perturbations and time scales (SPaTS) for WECS has been used earlier for variable speed and constant pitch (VS-CP) wind model and using the linearization of the nonlinear model. In this project, the model of the variable speed and variable pitch (VS-VP) turbine wind energy system is considered for study. The designing and integrating the model of the VS-VP system is a bit more complicated and challenging than that of the VS-CP model. Further, the VS-VP system contains both mechanical and electrical components giving rise to the slow and fast dynamics, respectively and hence exhibiting the time scales. Briefly, the SPaTS technique helps in expressing the system with low-order, outer (slow) dynamics and inner (fast) dynamics. The inner dynamics is also called boundary layer correction. In this project we consider VS-VP WECS model for the decoupling process to obtain low-order slow and fast subsystems. Next, using the advanced optimal control methods, two low-order, closed-loop, optimal, slow and fast sub-controllers are obtained. A composite optimal controller is constructed using the two slow and fast sub-controllers and applied to the original nonlinear wind energy system. Comparisons are made between the results of the system using the full-order, optimal controller and the low-order, optimal sub-controllers to validate the SPaTS strategy.Finally, some conclusions and future work are included.