A Review on Islanding Detection Schemes for DC Microgrids

Abstract

Recently, renewable energy sources (RESs)-based power plants have attained significant attention because of the fast depletion of fossil fuels and global warming [1]. Distributed generations (DGs), loads, and a bidirectional converter is interfaced with the utility grid in order to exchange powers [2]. DGs enhance the profit of power generation, reduce the effect of global warming, and improve power quality. Therefore, the application of DGs provides the reliability and security to the system [3,4]. MGs are of two types, namely AC MGs and DC MGs. Operation modes of MGs can be either isolated or grid-connected modes [5]. AC MGs research is well developed because of its mature technologies, protection, and standards. Most of the DGs generate power in the form of DC, and it is converted into AC power through DC-to-AC converter (inverter) in order to connect them with the AC MGs [6]. It is important to note that DC loads need DC power supply, and hence, AC power is converted back to DC power. Here, the number of conversions, number of required converters, and losses are more, so it reduces the efficiency of the system [7]. Apart from these, stability, synchronization, and reactive power requirement are the built-in disadvantages of AC MGs. Therefore, DC MGs are a better alternative and solution to the above problems [8,9]. Moreover, DC MGs are easily scalable because of the absence of limiting equipment, such as transformers and relays.During islanding, utility grid connection is absent. So, DGs are the main sources at this time. But, the power can reach to the consumers without any interruption during islanding due to DGs [10]. Here, employees can be affected by islanding as