# A Decentralized Multi-Agent-Based Approach for Low Voltage Microgrid Restoration
## 1 Introduction  
### Motivations  
Nowadays, the limited operating margins of the power systems have increased the risk of power blackouts and system collapse. In recent years, several major blackouts have occurred around the world. For instance, the blackout that occurred on 14 August 2003 in North America, caused an immense loss and the power system restoration (PSR) lasted nearly two weeks [1]. Also, a European power outage affected 15 million people on 4 November 2006, and it lasted up to 2 h. The blackout that occurred on 31 July 2012, in north India deenergized 50 GW of loads and affected 670 million people. The 2009 Brazil and Paraguay blackout was a power outage that occurred in many sections of Brazil and for a short time affected the entirety of Paraguay. The Fukushima nuclear power plant was faced with a series of equipment failures after the earthquake and tsunami on 11 March 2011, and a significant amount of radioactive materials were also released into ground and ocean waters [2]. When a blackout occurs, the main priority is to restore the power system in a proper manner so that the maximum load is restored as soon as possible considering the operating conditions and the system security.  
During the past years, various aspects of the PSR problem have been studied, and its theories and methods are largely mature [3; 4; 5; 6; 7]. In conventional power systems, the restoration process begins from the transmission system by starting up those power plants which provide the black start capability in the shortest time. This allows the supply of a large part of the consumers near the power plants and to energize the transmission network [4]. The start of the restoration process from the transmission system causes many consumers in the distribution system to be supplied in the final stages of the restoration process, so the reliability of the system is decreased.  
With the restructuring of the power grids toward smart grids which are based on the smart energy infrastructure consisting of microgrids (MGs) and distributed energy resources, the possibility of restoration of a large part of the loads at the distribution level along with restoration of the power plants and transmission network is provided. Therefore, the combination of the distributed energy resources and the flexible demands in the form of MGs can facilitate the implementation of local self-healing methods and accelerate the restoration process. In this sense, the PSR process can be carried out using a top-down procedure starting from the high voltage (HV) transmission system along with a bottom-up approach starting from the low voltage (LV) distribution system by using the capabilities of the LV MGs. The LV MGs and the HV transmission system will be synchronized and connect together at the medium voltage (MV) distribution level [8; 9; 10; 11].  
The motivation of this paper was to design and develop a decentralized multi-agent-based approach for restoration of a MG after a general blackout. The proposed decentralized approach provides an adequate restoration sequence to maximize the amount of restored loads.