Browsing by Subject "Microgrids"

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    Distributed Coordination and Control -- A bottom up design framework for Highly Renewable Grids and
    (2021-07) Patel, Sourav
    The modern power grid is undergoing an inflection point where the role of distributed energy resources (DERs) including renewable energy sources (RESs) has surpassed parity with conventional bulk power generation system as the prevalent source of energy generation. This transition from the conventional to modern power grids is also favored by economies of integrating distributed generation technologies, proliferation of intelligent communication devices such as sensors and data acquisition systems providing a global and persistent view into the state of the power system and, low footprint computational devices that have accelerated the distributed nature of the coordination of these DER units and if desired, to appear as a single aggregated unit to leverage the benefits of scale that a large centralized bulk power system can provide. Most of the design philosophy for the power-electronics interfaced DERs and highly renewable grid has been developed keeping in mind the operation of a conventional power system which is a large inertial system and highly centralized in nature. The existing grid needs to undergo transformations including control design methodologies keeping DERs and RESs at the focus and utilization of distributed communication algorithms at DERs allowing renewable energy resources and battery energy storage systems to participate in grid interactive services that can meet aggressive response timescales to maintain the operation and stability of the power system. This thesis makes several contributions, firstly towards enabling better active and harmonic power sharing in multi-inverter microgrid systems (MMGs) with DERs interfaced with low-inertia voltage source inverters (VSIs) while reducing the complexity of reactive power sharing and control. Secondly, investigations and contributions towards developing a novel aggregation strategy and implementation methodology for smaller DER units for enabling challenging grid interactive services in presence of real-world non-idealities such as time delay in communication channel are also presented and validated by developing a novel end-to-end power-hardware-in-the-loop (PHIL) configuration. The finite-time termination distributed schemes suffer from vulnerability to cyber-attacks that are aimed at manipulating data and control flow. In the final part we develop a novel distributed method for detecting the presence of such intruders for a multi-agent system implementing ratio consensus protocol.
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    Spatio-temporal model reduction of inverter-based islanded microgrids
    (2014-01) Luo, Ling
    Microgrids, are small foot-print power systems that balance critical loads against available energy supply, and are capable of operating in both grid-connected and islanded operation modes. Numerous factors such as energy assurance, reliability, renewable integration and economics are driving increased research and development in the modeling, analysis and control of microgrids.In intentionally islanded operation, well-established droop control techniques are employed to keep inverters synchronized and regulate frequency and voltage within stability limits in microgrids. Computationally efficient and accurate models that describe droop-controlled inverter dynamics are key to controller design, stability assessment, and performance evaluation of islanded microgrids. Typical models for droop-controlled inverters are very detailed, and include myriad states from internal control loops and filters. Conceivably, control design, numerical simulations, and stability assessment with such models in islanded microgrids comprising tens of or even hundreds of inverters is computationally expensive and do not offer any analytical insights. This calls for the development of reduced-order models of inverter-based microgrids. Model reduction methods can isolate relevant spatio-temporal dynamics and mutual interactions of interest. While model reduction methods have been widely applied in bulk power systems, a systematic model-reduction procedure for droop-controlled islanded inverters has thus far been lacking. The objective of this thesis is to reduce large-signal dynamic models of inverter-based islanded microgrids in both spatial and temporal aspects. Singular perturbation methods are applied for temporal model reduction, and Kron reduction is employed for the spatial model reduction. The ensuing reduced-order models accurately describe the original dynamics with reduced computational burden. In addition, spatial model reduction isolates the mutual inverter interactions and clearly illustrates the equivalent loads that the inverters have to support in the microgrid - this aspect is leveraged in controller design to minimize power losses and voltage deviations.