US 11,757,278 B1
Method and system for fault location and protection of inverter-dominated islanded ungrounded microgrids
Hongbo Sun, Cambridge, MA (US); and Fangyuan Chang, Cambridge, MA (US)
Assigned to Mitsubishi Electric Research Laboratories, Inc., Cambridge, MA (US)
Filed by Mitsubishi Electric Research Laboratories, Inc., Cambridge, MA (US)
Filed on Mar. 9, 2022, as Appl. No. 17/654,176.
Int. Cl. H02H 3/26 (2006.01); H02H 1/00 (2006.01)
CPC H02H 3/265 (2013.01) [H02H 1/0092 (2013.01)] 22 Claims
OG exemplary drawing
 
1. A computer-implemented method for protecting a power grid system including a primary bus and an islanded microgrid disconnected from a distribution system, the islanded microgrid forming branches from the primary bus, the islanded microgrid including at least one distributed generator (DG), each DG including at least one switchable device to separate power supply of the DG from the power grid, each of the branches including a first terminal sensor arranged at a near side of the primary bus and a second terminal sensor arranged at opposite terminal bus of the branch, the first terminal and second terminal sensors indicating a branch location of each of the branches in the power grid, wherein the method uses a processor coupled with a memory stored instructions implementing the method, wherein the instructions, when executed by the processor carry out at steps of the method, comprising:
receiving, from each of the branches, measurement data including the branch location from the first terminal sensor and the second terminal sensor, wherein the measurement data include zero-sequence currents of the first terminal sensor and the second terminal sensor, negative-sequence currents of the first terminal sensor and the second terminal sensor, and phase currents of the first terminal sensor and the second terminal sensor;
determining a branch indicating a fault status among the branches if there is approximately a 180-degree phase angle difference between the zero-sequence currents, if a difference amount between the negative-sequence currents of the first and second terminal sensors at the branch is equal to or greater than a threshold, or if a difference of signs of any phase currents as a function of time indicates transitions between zero and two; and
transmitting a control command to the at least one switchable device that is configured to isolate the determined branch indicating the fault status from the at least one DG, wherein the at least one switchable device is determined based on a distance from the at least one switchable device to the determined branch, wherein the control command instructs the switchable device to disconnect the determined branch from the at least one DG.