Date of Completion

12-13-2017

Embargo Period

12-13-2017

Keywords

Microgrids, Software-Defined Networking

Major Advisor

Peng Zhang

Associate Advisor

Peter B. Luh

Associate Advisor

Bing Wang

Field of Study

Electrical Engineering

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Multiple major blackouts had occurred in the U.S. power distribution system highlighting the importance of enhancing electricity resiliency. Microgrid is the new paradigm incorporating high flexibility and reliability in power supply. It allows various distributed energy resources and loads to be integrated and coordinated as an intelligent entity through control and communication infrastructure. Microgrid control technologies have been continuously developed over 20 years. However, there is still a lack of communication architecture that is able to provide fast, reliable and elastic services for multi-level data transmission and adaptable network management. This dissertation solves this intractable problem by integrating programmable networks into microgrid to provide flexible and easy-to-manage communication solutions, thus enabling resilient microgrid operations in face of various cyber and physical disturbances. Both theoretical study and experimental tests have shown that the novel software-defined networking (SDN) based communication architecture can significantly improve the microgrid emergency control performance and expedite the development of microgrid applications. While providing resilience benefits to its local customers, a single microgrid can hardly contribute to the resiliency of the main distribution grid. Recent research shows interconnecting individual microgrids to form a networked microgrids community offers a new, more resilient solution for distribution grid. To support this innovation, this dissertation significantly extends the SDN-based communication architecture to achieve fast power support among microgrids, transforming isolated local microgrids into integrated networked microgrids capable of achieving the desired resiliency, elasticity and efficiency. Further, a novel event-triggered communication scheme is devised to enable distributed power sharing among microgrids in both the transient period and the steady state, a capability previously unattainable using existing technologies. This structure is validated through a cyber-physical Hardware-in-the-Loop (HIL) testbed designed in this dissertation for testing and prototyping networked microgrids technologies. One of the multifaceted benefits of the SDN-based architecture is that it provides a platform with open data access for the development of various advanced microgrid applications. As an instance, a generalized microgrid power flow (GMPF) algorithm is developed as an essential tool for control design and microgrid planning. Power flow analysis for islanded microgrid is a challenging problem due to the lack of means to incorporate the hierarchical control effect. This dissertation bridges the gap by introducing three novel GMPF techniques: 1) it introduces the generalized distributed generator (DG) bus and the adaptive swing bus to model the DGs’ behaviors; 2) the droop based power flow is used to initialize the secondary control adjustment; and 3) three types of secondary control modes are developed within a double loop framework. GMPF has proved to have excellent convergence performance and be able to provide information of power sharing and voltage regulation under different control modes, which makes it a powerful tool for microgrid planning, control design, and energy management, etc..

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