US 12,431,703 B2
Weak-signal fault identification of inverter-based microgrids
Hongbo Sun, Cambridge, MA (US); Imtiaj Khan, Cambridge, MA (US); Kyeong Jin Kim, Cambridge, MA (US); and Jianlin Guo, 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. 24, 2023, as Appl. No. 18/189,529.
Prior Publication US 2024/0322555 A1, Sep. 26, 2024
Int. Cl. H02H 7/22 (2006.01); H02H 1/00 (2006.01)
CPC H02H 7/22 (2013.01) [H02H 1/0092 (2013.01)] 21 Claims
OG exemplary drawing
 
1. A system for identifying an existence, location and type of a weak-signal fault in a microgrid, wherein the microgrid is connected to a main grid equivalenced as a synchronous generator, and includes at least one branch, the at least one branch including at least one line segment connected between two buses, wherein at least one of the two buses is connected with a synchronous generator, at least one bus being connected with a grid forming inverter (GFM), at least one bus being connected with a grid following inverter (GFL), and at least one bus being connected with a load, at least two switches being connected to different locations of the at least one branch, wherein each of the at least two switches is equipped with an intelligent electronic device (IED) configured to monitor and control at least one switch, wherein the microgrid is operated at islanded mode, comprising:
at least one processor; and a memory having instructions stored thereon that cause the at least one processor to perform steps of:
receiving timeseries measurements of currents and voltages from at least two IEDs installed in the microgrid;
denoising the timeseries measurements by a discrete wavelet transform (DWT) algorithm;
detecting if each of the denoised timeseries measurements indicates a weak-signal fault occurred by a frequency components analysis using a variational mode decomposition (VMD) algorithm, wherein when the weak-signal fault is detected, the at least one processor further performs:
identifying if the weak-signal fault is an inverter-related fault or a high impedance fault, wherein for the identified inverter-related fault, a fault location is determined according to currents and voltages at AC side of corresponding inverter, wherein for the high impedance fault, fault candidate locations are determined using correlation between timeseries components of the denoised timeseries measurements between the at least two IEDs for each of the at least one branch and the fault location of the weak-signal fault based on the fault candidate locations by identifying a branch containing the weak-signal fault using a timeseries K-nearest neighbors (KNN) model and a neighbor distance measured by a dynamic time warping (DTW) algorithm;
identifying a fault type of the determined weak-signal fault using a fault classification logic circuit according to variation statuses of sequence components and phasor measurements over a fault period;
producing a fault identification command indicative of the fault location and the identified fault type; and
isolating and restoring the microgrid according to the fault identification command by transmitting control signals of the fault identification command to a microgrid controller of the microgrid.