Abstract
Due to the interconnected scheme of multiple components, such as distributed generators, storage systems, and loads through converters to a common bus in DC microgrids, the possibility of fault occurrence is increasing significantly. Meanwhile, due to the huge and rapid increase of short-circuit currents, the development of a small- and large-scale DC system requires a reliable and fast protection system to ensure fault clearance and maintain safety for the rest of the system. Thus, fault protection has been focused on as one of the most critical issues in a direct current network. The application of traditional circuit-breakers for DC fault protection has the drawback of slow operation, which requires a high rating power equipment. Recently, the high speed and excellent performance capabilities of semiconductor breakers have attracted a lot of attention and been considered as an optimal solution for fast DC fault interruption. In this study, a bidirectional Insulated-Gate Bipolar Transistor (IGBT) semiconductor breaker, suitable for the fault protection of low-voltage DC networks, is proposed. The operating characteristics of this breaker are based on changes in the circuit current and terminal voltage of IGBTs. It detects the abrupt change of the terminal voltage as an abnormal condition and isolates the faulted branch in a short time to prevent the operation disturbance in the healthy part of the network. Therefore, for the entire protection of a typical 400V DC-microgrid cluster, breakers need to be integrated and examined in each branch and the interconnected lines. The proposed protection method in this study is examined in a Simulink®/MATLAB environment to analyze and assess its operation.
Highlights
A stand-alone DC microgrid is an independent, controllable, small-scale electrical system in the presence of Distributed Generators (DGs), controllable and non-controllable loads, power electronic components, and protective devices [1]
Smaller arcing: For any type of circuit breaker, electric arcing should be suppressed and decreased to prolong the lifetime of the CB itself and ensure tripping of the faulted circuit; Completely controllable: The connecting and disconnecting of CB needs to be completely controllable, either by automatic mechanical tripping or digital controllers; Operating speed: CBs for DC fault interruption are required to have an interrupting capability of fault currents with high speed to avoid huge short-circuit currents and destruction of the components; Operational loss: The efficiency of CB should be appropriate for the normal operation of the system
The simulation results for the current, voltage waveforms, and State of Charge (SoC) of the battery during the fault conditions are depicted in the following figures
Summary
A stand-alone DC microgrid is an independent, controllable, small-scale electrical system in the presence of Distributed Generators (DGs), controllable and non-controllable loads, power electronic components, and protective devices [1]. High- and low-voltage DC systems are recognized as an efficient method for power transmission and distribution. Since Edison’s time, the DC system has been implemented for energy supply purposes, but due to the lack of standards and technologies, AC system. Sci. 2019, 9, 723 have been leading the DC network. Whereas the emerging of new power electronics and distributed energy resource technologies have made it easier to interconnect power components and build a multi-terminal DC system. DC short-circuit protection is still considered to be one of the major challenges for DC network applications in terms of small- and large-scale power transmission and distribution [2]
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