Distributed Optimal Energy Management in Microgrids

TLDR

Energy management in microgrids is a nonlinear optimization problem that, when solved centrally, demands high computational resources and can compromise customer privacy, while existing distributed methods assume a single bus and ignore network constraints, producing potentially infeasible schedules. This paper designs a distributed energy management strategy that optimally operates microgrids while accounting for the distribution network and its operational constraints. The authors formulate the problem as an optimal power flow and implement a distributed EMS—where the MGCC and local controllers jointly compute schedules—based on IEC 61850 and test it on a real Guangdong microgrid with photovoltaics, wind turbines, diesel generators, and battery storage. Simulation results show the proposed distributed EMS converges quickly and is effective.

Abstract

Energy management in microgrids is typically formulated as a nonlinear optimization problem. Solving it in a centralized manner does not only require high computational capabilities at the microgrid central controller (MGCC), but may also infringe customer privacy. Existing distributed approaches, on the other hand, assume that all generations and loads are connected to one bus, and ignore the underlying power distribution network and the associated power flow and system operational constraints. Consequently, the schedules produced by those algorithms may violate those constraints and thus are not feasible in practice. Therefore, the focus of this paper is on the design of a distributed energy management strategy (EMS) for the optimal operation of microgrids with consideration of the distribution network and the associated constraints. Specifically, we formulate microgrid energy management as an optimal power flow problem, and propose a distributed EMS where the MGCC and the local controllers jointly compute an optimal schedule. We also provide an implementation of the proposed distributed EMS based on IEC 61850. As one demonstration, we apply the proposed distributed EMS to a real microgrid in Guangdong Province, China, consisting of photovoltaics, wind turbines, diesel generators, and a battery energy storage system. The simulation results demonstrate the effectiveness and fast convergence of the proposed distributed EMS.