Microgrids: Hierarchical Control and an Overview of the Control and Reserve Management Strategies

TLDR

The growing penetration of distributed generation creates congestion and voltage issues in distribution networks, prompting the use of microgrids that aggregate DG, controllable loads, and storage and can operate in grid‑connected or islanded mode, where hierarchical control structures—primary, secondary, and tertiary—have been explored and classified as local or centralized. This article aims to discuss hierarchical control for microgrids and provide an overview of control strategies for reserve provision by DG units, loads, and storage, enabling coordinated frequency and voltage regulation. The study focuses on islanded microgrids, describing a hierarchical control architecture that integrates primary, secondary, and tertiary layers—implemented locally or centrally—to manage reserve provision from DG, loads, and storage.

Abstract

The increasing share of distributed generation (DG) units in the electrical power systems has a significant impact on the operation of the distribution networks which are increasingly being confronted with congestion and voltage problems. This demands for a coordinated approach for integrating DG in the network, allowing the DG units to actively contribute in the frequency and voltage regulation. Microgrids can provide such coordination by aggregating DG, (controllable) loads and storage in small-scale networks, that can operate both in grid-connected and islanded mode. Here, the islanded operating condition is considered. Analogous as in the conventional networks, a hierarchical control structure can be implemented in islanded microgrids. In recent years, many different concepts for primary, secondary and tertiary control of microgrids have been investigated. These controllers can be classified as either local or centralized. In this article, the hierarchical control for application in microgrids is discussed and an overview of the control strategies is given with respect to the reserve provision by the DG units, loads and storage equipment.