Transient stability analysis of an islanded microgrid under variable load Muhammad Babar Rasheed 1 , Muhammad Awais 2 , Nadeem Javaid 1,* , Waseem Nazar 2 , Umar Qasim 3 , Zahoor Ali Khan 4 1 COMSATS Institute of Information Technology, Islamabad, 44000, Pakistan 2 The University of Lahore, Lahore 54000, Pakistan 3 University of Alberta, Edmonton, AB, T6G 2J8, Canada 4 CIS, Higher Colleges of Technology, Fujairah Campus, 4114, UAE * Correspondence: nadeemjavaidqau@gmail.com; www.njavaid.com Abstract—In this paper, we investigate some aspects related to microgrid (MG) stability. Due to different applications of MG, its structure and deployment topology vary depending upon the nature of application and operating modes (islanded or grid connected). So, the stability of MGs varies accordingly. This paper precisely explains the stability aspects (e.g., phase angle and power losses) of remotely located islanded MG having the capability to integrate distributed energy sources. Initially, the stability of three bus system is assessed under variable load and find some gaps related to stability as MG involves a high penetration of distributed energy sources. These gaps indicate that stability of a MG is not only in the control of generation/load but also in its coordination with other loads. After that, we implement the load coordination technique and analyze the stability against fixed and dynamic loads. For comprehensive analysis, four different cases are considered in which we vary load at different bus bars and check the performance. Lastly, we integrate the distributed energy source to islanded MG and perform the stability analysis. For validation purpose, extensive simulations of the proposed cases are conducted using Matlab. Simulation results depict that load coordination technique is more efficient regarding MG stability. Index Terms—Smart Grid, Microgrid, Stability, Coordination and control, Power losses I. I NTRODUCTION AND BACKGROUND MGs are interconnected and intelligent power distribution networks consisting of distributed generation, storage, and loads. Based upon the location and energy demand, MG systems can work in two different modes: the grid connected mode when power supply is provided by the utility grid and the islanded mode when local generation is available [1], [2]. Due to ever increasing energy demand in the world, MG vision has come to include the distributed renewable energy sources into main grid to fulfil the energy demand. This concept allows the MG to operate in an islanded or grid connected mode in case when main power is unavailable due to faults or shortage of energy. So, in power systems, both renewable and dispatchable distributed energy sources can be integrated. Due to this facility, the core of MG concept is to integrate distributed energy sources alongwith main supply to reduce carbon-dioxide emissions and electricity cost and improve the stability of the MG by reducing power losses (Fig. 1). However, due to unpredictable nature of distributed energy sources and energy demand variations at different time spans raise a serious stability problem [3]. The integration of distributed energy sources is one of the most efficient solutions in providing energy to end users with high reliability and affordable cost [4]. However, without coordination between utility, distributed generation and end users, it is difficult to achieve reliable operation having minimum power losses. Fig. 1. One-line diagram of 3-bus power system Recently, authors have proposed different techniques regard- ing energy management to reduce power losses with improved system stability. In [5], [6], authors propose MG coupling scheme using interconnecting static switch. The neighbouring grids have been connected to avoid possible overload condi- tions due to uneven energy demand. Network tertiary control scheme is utilized where self-healing agent is introduced to decide which MG has power deficiency and which has excess power. Based upon this information, agent decides which MG will be connected after islanding mode. The proposed scheme is validated using PSCAD/EMTDC software. In addition, this scheme avoids the traditional load shedding mechanism which affects the end user comfort. In [7], authors use synergistic 2016 19th International Conference on Network-Based Information Systems 2157-0426/16 $31.00 © 2016 IEEE DOI 10.1109/NBiS.2016.79 196