Microgrid Interconnections Control via Voltage Angle Droop Methods
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abstract
This project proposes a novel system configuration for a future distribution grid in which multiple microgrids are coupled through distribution lines and present themselves as individual controllable entities. Built upon the innovations on sensors (micro-synchrophasors) and actuators (power electronic interfaces), we envision a future distribution grid to be comprised of many microgrid clusters, each interfacing through points of common coupling with little or no inertia. It is anticipated that the results of this project will help many communities (such as rural and developing regions) to leapfrog the century-old distribution grid through an envisioned clean slate approach to integrating a much deeper level of renewable resources at a much higher level of reliability. The project will provide a fresh perspective on inspiring students to engineer a qualitatively different electricity delivery system that is tailored for the paradigm shift in both sensing and control technologies. Housed at one of the largest university power/energy programs in the U.S., this team will introduce new course modules on the topic of the future distribution grid, which closely integrates power electronics and power systems background knowledge for more than 200 undergraduate and graduate students currently enrolled in power courses at Texas A&M. This team will continue a strong track record of engaging undergraduate students for research, in particular underrepresented groups. The prototype and simulation visualization will be presented at the annual "Discover ECE" event, which attracts more than 300 high school students and parents annually.The scientific objective of this project is to investigate novel power electronic interfaces, as well as the control of microgrid clusters for ensuring dynamic security at the distribution grid level. The project will address the following questions: a) how should an all-DC or AC microgrid interact with distribution systems through an appropriately designed power electronics interface; and b) what would be a control architecture that leverages advances from power electronics and sensors, and achieves provable dynamical performance. This project puts forward a truly interdisciplinary research agenda to leverage power electronics and control for advancing the distribution grid sciences. The cross-fertilization of power systems and power electronics will provide fresh perspectives for the future distribution grid. The intellectual merit of this project is four fold. First, the research team will investigate the possibility of guaranteeing distribution system-level transient stability via distributed droop management. This difficult problem will draw upon the structure of the closed-loop microgrid module dynamics, which, in turn, lends the distribution grid transient model as a Lur''e system with time invariant sector bounded memoryless nonlinearities. Second, the project will introduce a multiple points of common coupling (PCC) control of a microgrid when it has multiple connections with distribution systems. This will allow for decomposing an MW-level inverter into multiple lower rating inverters with much lower cost and increase in reliability. Third, for the case of DC microgrids with MWs of capacity, a closed loop iterative process of adjusting the output voltage and phase angle for voltage source inverters with finite LC output filter impedance will be will introduced and tested. Fourth, for the case of AC microgrids, an optimal power electronic transformer topology (with fault tolerant features) will be developed to achieve the wide range of voltage magnitude and angle adjustments at fast response as required by the microgrid angle droop dynamic control approach enabled by modern micro-synchrophasors. Prior art methods for voltage/angle adjustment are both slow in response and limited in range, rendering them unsuitable for the proposed control architecture.
