Practical computation of di/dt for high-speed protection of DC microgrids

DC microgrids have the potential to radically disrupt the distribution system market due to the benefits offered in easing the integration and control of distributed renewable energy resources and energy storage systems. However, the non-zero-crossing fault current profiles associated with short-circuited DC systems present a major challenge for protection. Isolation of faulted networks prior to the peak-current discharge of DC-side capacitors may address this challenge if rapid fault detection speeds (shorter than 2ms) can be achieved. Accordingly, novel methods of utilising the rate-of-change-of-current (di/dt) have been proposed in the literature to realize new, high-speed distance protection strategies. This paper proposes two practical methods for optimizing the numerical computation of di/dt of fault current transients and evaluates the performance of each within a MATLAB/Simulink model of a DC microgrid with artificially injected measurement noise.