Distributed Secondary Control of Hybrid ac/dc Microgrids

Abstract

This thesis focuses on studying hybrid ac/dc-microgrids, composed of an ac-microgrid and a dc-microgrid, connected by Interlinking Converters (ICs). Specifically, this work is focused on developing distributed secondary controllers that consider the hybrid microgrid as a single entity and not as three independent systems interacting with each other. The main goal of the secondary controller is augmented with one of the following objectives: (i) achieving active power consensus between ac-DGs and dc-DGs (and ICs), or (ii) minimizing the operation cost of the microgrid. The additional control task is performed with information from the nearest neighbours from both sides of the microgrid. Two analytical closed-loop models for a hybrid microgrid are obtained in this thesis. The first one considers the consensus-based distributed control strategy proposed for active power consensus. In contrast, the second one considers the strategy proposed for minimizing the operation cost of the microgrid. The closed-loop models are used to perform several analyses of the control systems proposed. Several tests are carried out to validate the performance of the proposed control strategies in two different topologies: a 24kW prototype with a single IC and a 33kW prototype with multiple ICs.