Design and Simulation of a High-Frequency Protection Scheme for DC Microgrid Line Systems

As an effective access method for renewable energy, the application scenarios of Direct Current (Hereinafter referred to as DC) microgrids are gradually increasing. However, in comparison with the traditional Alternating Current (Hereinafter referred to as AC) power system, the DC system fault current rises rapidly and with a significant amplitude, which results in considerable mechanical stress and overheating on the power lines and equipment. Consequently, the rapid fault location and removal have become the pivotal issues of DC systems that require urgent resolution. In this paper, we This paper proposes a high-frequency protection system for DC microgrid lines. The system extracts the high-frequency component of the fault by fast Fourier transformation (FFT) when the fault occurs and uses this component to judge whether it meets the action conditions of each segment protection. When the action conditions are met, the protection I and II sections cooperate with each other to selectively isolate the fault from the line, thus ensuring the safety of DC microgrid operation. During the fault, the equivalent impedance of the high-frequency components generated by the DC/DC converters on both sides of the line is minimal, forming an evident fault boundary within the fault line. This boundary can be utilized to rapidly ascertain the fault location. This paper is based on the PSCAD/EMTDC 4 simulation platform for model construction, design experiments, and simulation verification. This paper presents a simulation study of inter-pole short-circuit faults and high-frequency protection schemes for flexible DC microgrids. The performance of the protection system in the event of an inter-pole short-circuit at different locations along DC lines is evaluated. The results demonstrate that the high-frequency overcurrent protection can satisfy the selectivity, reliability, sensitivity, and rapid response requirements of DC microgrid protection.