*Article* **An Improved Power Management Strategy for MAS-Based Distributed Control of DC Microgrid under Communication Network Problems**

#### **Thanh Van Nguyen and Kyeong-Hwa Kim \***

Department of Electrical and Information Engineering, Seoul National University of Science and Technology, 232 Gongneung-ro, Nowon-gu, Seoul 01811, Korea; vanthanhpro94@gmail.com

**\*** Correspondence: k2h1@seoultech.ac.kr; Tel.: +82-2-970-6406

Received: 29 November 2019; Accepted: 20 December 2019; Published: 22 December 2019

**Abstract:** In this paper, an improved power managemen<sup>t</sup> strategy (PMS) for multi-agent system (MAS)-based distributed control of DC microgrid (DCMG) under communication network problems is presented in order to enhance the reliability of DCMG and to ensure the system power balance under various conditions. To implement MAS-based distributed control, a communication network is constructed to exchange information among agents. Based on the information obtained from communication and local measurements, the decision for the local controller and communication is optimally given to guarantee the system power balance under various conditions. The operating modes of the agents can be determined locally without introducing any central controller. Simultaneously, the agents can operate in a deliberative and cooperative manner to ensure global optimization by means of the communication network. Furthermore, to prevent the system power imbalance caused by the delay in grid fault detection and communication in case of the grid fault, a DC-link voltage (DCV) restoration algorithm is proposed in this study. In addition, to avoid the conflict in the DCV control among power agents in case of the grid recovery under communication failure, a grid recovery identification algorithm is also proposed to improve the reliability of DCMG operation. In this scheme, a special current pattern is generated on the DC-link at the instant of the grid recovery by the grid agent, and other power agents identify the grid recovery by detecting this current pattern. Comprehensive simulations and experiments based on DCMG testbed have been carried out to prove the e ffectiveness of the PMS and the proposed control schemes under various conditions.

**Keywords:** communication network problems; DC microgrid; distributed control; improved power management; multi-agent systems; grid recovery
