A Smart and Flexible Microgrid With a Low-Cost Scalable Open-Source Controller

Abstract

In contrast with conventional microgrids (MGs) with fixed boundaries, a smart and flexible MG with dynamic boundary is introduced in this paper. Such a MG can dynamically change its boundary by picking up or shedding load sections of a distribution feeder depending on its available power, leading to more flexible operation, better utilization of renewables, smaller size of energy storage system, higher reliability, and lower cost. To achieve a flexible MG, the main challenges in MG design are addressed, including recloser placement, MG asset sizing considering resilience, system grounding design, and protection system design. Meanwhile, a hierarchical structure is employed to design and implement the MG controller. On top of the functions defined in IEEE 2030.7-2018, a few new functions, e.g., online topology identification and PQ balance, are added, while the planned/unplanned islanding and reconnection functions are enhanced. The controller is implemented on a CompactRIO, a general-purpose hardware platform provided by National Instruments (NI), and tested on a controller hardware-in-the-loop setup based on an OPAL-RT real-time simulator and a reconfigurable power electronic converter-based hardware testbed. The test results have validated the performance of the developed controllers. Such a flexible MG and its controller have been deployed at a municipal utility, and part of the controller's functions have been tested on-site.

Real-Time Power Management for Microgrids With Dynamic Boundaries and Multiple Source Locations

“…The controllers described in this paper are being deployed at a community microgrid operated by EPB near the Chattanooga, TN airport [20], and the controller continues to improve and cover more emerging needs from the field application, such as load imbalance monitoring and control, proactive reactive power balancing through switching capacitor banks, and coordination with utility SCADA/DMS and existing protection schemes.…”

“…The microgrid controllers developed at the University of Tennessee aim to facilitate fast, scalable, and low-cost deployment of microgrid solutions [20]. The control solution is hierarchically structured with a microgrid central controller (MGCC) and several local controllers (MGLC) depending on the number and location of controllable DERs.…”

“…The actual design of the microgrid in the field, however, is an overarching effort that covers all subsystems, including recloser placement, resource sizing, grounding system, and protection system design, to achieve a balance between cost and reliability. We have had publications and are preparing a dedicated manuscript regarding the design topic to address specific concerns and opportunities in microgrid design arising from multiple-source-location dynamic-boundary microgrids [20]…”

A Negative Sequence Impedance Design and Regulation Strategy for Negative Sequence Current Sharing Among Grid-Forming Sources in Microgrids Considering Topology Impacts

“…Unbalanced loads require sufficient NS current capability of DERs. In a MG with multiple sources, to meet the unbalanced load current needs, overdesigning the NS capabilities of all sources is usually a direct solution, but it is not cost-efficient [3]. Accurate control of NS current sharing among sources enables the distribution of NS currents among sources with a specific objective, allowing for lower but safe NS current requirements on individual sources.…”

Service Restoration Through Microgrid Formation in Distribution Networks: A Review

“…Both planned and unplanned islanding operations could be used in service restoration for distribution networks during severe events to supply load in their original or extended boundary. Based on their boundary [28]: microgrids can be divided into pre-determined microgrids and dynamic microgrids.…”