Browsing by Subject "energy storage"
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Item Integration of Electric Energy Storage into Power Systems with Renewable Energy Resources(2012-10-26) Xu, Yixing 1985-This dissertation investigates the distribution and transmission systems reliability and economic impact of energy storage and renewable energy integration. The reliability and economy evaluation framework is presented. Novel operation strategies of energy storage and renewable energy are proposed. The method for optimizing the energy storage sizing and operation strategy in order to achieve optimal reliability and economy level is developed. The objectives of the movement towards the smart grid include making the power systems more reliable and economically efficient. The rapid development of the large scale energy storage technology makes it an excellent candidate in achieving these goals. A novel Model Predictive Control (MPC)-based operation strategy is proposed to optimally manage the charging and discharging operation of energy storage in order to minimize the energy purchasing cost for a distribution system load aggregator in power markets. Different operation strategies of energy storage have different reliability and economic impact on power systems. Simulation results illustrate the importance of the energy storage operation strategies. A hybrid operation strategy which combines the MPC-based operation strategy and the standby backup operation strategy is proposed to flexibly adjust the reliability and economic improvement brought by energy storage. A particle swarm optimization approach is developed to determine the optimal energy storage sizing and operation strategy while maximizing reliability and economic improvement. A reliability and economy assessment framework based on sequential Monte Carlo method integrated with the operation strategies is proposed. The impact on the transmission systems reliability brought by energy storage and renewable energy with the proposed operation strategies is investigated. Case studies are conducted to demonstrate the effectiveness of the proposed operation strategies, optimization approach, and the reliability and economy evaluation framework. Insights into how energy storage and renewable energy affect power system reliability and economy are obtained.Item Multilevel Converter Topologies for Utility Scale Solar Photovoltaic Power Systems(2014-04-30) Essakiappan, SomasundaramRenewable energy technologies have been growing in their installed capacity rapidly over the past few years. This growth in solar, wind and other technologies is fueled by state incentives, renewable energy mandates, increased fossil fuel prices and environmental consciousness. Utility scale systems form a substantial portion of electricity capacity addition in modern times. This sets the stage for research activity to explore new efficient, compact and alternative power electronic topologies to integrate sources like photovoltaics (PV) to the utility grid, some of which are multilevel topologies. Multilevel topologies allow for use of lower voltage semiconductor devices than two-level converters. They also produce lower distortion output voltage waveforms. This dissertation proposes a cascaded multilevel converter with medium frequency AC link which reduces the size of DC bus capacitor and also eliminates power imbalance between the three phases. A control strategy which modulates the output voltage magnitude and phase angle of the inverter cells is proposed. This improves differential power processing amongst cells while keeping the voltage and current ratings of the devices low. A battery energy storage system for the multilevel PV converter has also been proposed. Renewable technologies such as PV and wind suffer from varying degrees of intermittency, depending on the geographical location. With increased installation of these sources, management of intermittency is critical to the stability of the grid. The proposed battery system is rated at 10% of the plant it is designed to support. Energy is stored and extracted by means of a bidirectional DC-DC converter connected to the PV DC bus. Different battery chemistries available for this application are also discussed. In this dissertation, the analyses of common mode voltages and currents in various PV topologies are detailed. The grid integration of PV power employs a combination of pulse width modulation (PWM) DC-DC converters and inverters. Due to their fast switching nature a common mode voltage is generated with respect to the ground, inducing a circulating current through the ground capacitance. Common mode voltages lead to increased voltage stress, electromagnetic interference and malfunctioning of ground fault protection systems. Common mode voltages and currents present in high and low power PV systems are analyzed and mitigation strategies such as common mode filter and transformer shielding are proposed to minimize them.Item Risk Aware Robust Decision Making in Power Systems with Renewable Resources(2014-10-29) Thatte, Anupam AjitThe increasing penetration of renewable generation poses significant risks to the reliable operation of power systems, mainly due to the variable and uncertain nature of the output of wind and solar resources. This dissertation presents a robust optimization based decision making framework in future power systems with high penetration of variable renewable resources. The first part of this dissertation involves the modeling and analysis of a robust optimization based bidding strategy for the combination of a wind farm and an energy storage device participating in a deregulated electricity market. The selection of the uncertainty set for the robust optimization problem, based on the decision maker?s risk preference, is also discussed. From the market participant?s point of view improved utilization of the renewable resource, through storage enabled energy arbitrage, can lead to better economic performance. The storage device can provide firming power to the output of the wind farm, enabling the renewable resource to participate in the electricity market. The robust optimization based approach is compared to a deterministic optimization based approach through a numerical example. The second part of this dissertation investigates the metric and the dispatch method needed for a more robust real-time market operation. A novel metric for evaluating system-wide ramp flexibility is proposed. A robust framework to ensure the reliable dispatch of generators is presented and analyzed. The robust model is compared to both the conventional economic dispatch as well as a proposed industry approach to managing system flexibility called the look-ahead dispatch. Furthermore, the formulation for a robust multi-zonal dispatch model is presented. The proposed robust model and flexibility index is demonstrated through a numerical on a modified IEEE 24 Bus Reliability Test System.