Bidirectional protection for DC systems based on di/dt behavior

Abstract

The modern electric power systems are going through a revolutionary change due the development of DC loads and higher efficiency of DC systems where DC microgrids have some attractive characteristics, however they have several challenges such as limiting and interrupting fault current. In this paper, a protection for DC systems based on transient di/dt detection is proposed to provide faster short-circuit and overcurrent fault detection, where DC breakers are required to be designed for bidirectional fault current conditions, which is a challenge regarding DC microgrid applications due to some associated problems such as long periods of fault interruption, complex circuit structure, and low reliability. The proposal can detect fault current conditions for different distances from the point of failure, and is suitable to operation in both islanding and grid connected conditions. The proposed circuit was analyzed theoretically and experimentally in steady state, as well as under load changes and short circuit conditions to ensure proper operation, making this solution a suitable fast current fault DC breaker solution, which is a significant advantage and requirement in protection of DC systems.