Energy Management of Microgrid in Grid-Connected and Stand-Alone Modes

TLDR

Microgrids operate in either grid‑connected mode, where they are linked to the main grid most of the time, or stand‑alone mode, where they prioritize reliable power supply over economic benefits, leading to different energy‑management objectives. This study introduces a novel double‑layer coordinated control strategy for microgrid energy management. The strategy comprises a schedule layer that generates an economic operation plan from forecast data and a dispatch layer that supplies controllable‑unit power from real‑time data, coordinating the two layers by reserving active power in the schedule layer and reallocating it in the dispatch layer to correct forecast–real‑time discrepancies. Simulations on a typical‑structure microgrid demonstrate that the double‑layer coordination improves performance in both grid‑connected and stand‑alone modes.

Abstract

There are two operation modes of microgrids: grid-connected mode and stand-alone mode. Normally, a microgrid will be connected to the main grid for the majority of time, i.e., operates in the grid-connected mode. In the stand-alone mode, a microgrid is isolated from the main grid; the highest priority for microgrids is to keep a reliable power supply to customers instead of economic benefits. So, the objectives and energy management strategies are different in two modes. In this paper, a novel double-layer coordinated control approach for microgrid energy management is proposed, which consists of two layers: the schedule layer and the dispatch layer. The schedule layer obtains an economic operation scheme based on forecasting data, while the dispatch layer provides power of controllable units based on real-time data. Errors between the forecasting and real-time data are resolved through coordination control of the two layers by reserving adequate active power in the schedule layer, then allocating that reserve in the dispatch layer to deal with the indeterminacy of uncontrollable units. A typical-structure microgrid is studied as an example, and simulation results are presented to demonstrate the performance of the proposed double-layer coordination control method in both grid-connected mode and stand-alone mode.