US 2024/0255584 A1 · ISOLATION FOREST-BASED MODULAR MULTILEVEL CONVERTER OPEN-CIRCUIT FAULT DIAGNOSIS METHOD DEVICES

Abstract

The present invention discloses an isolation forest (IF)-based modular multilevel converter (MMC) open-circuit (OC) fault diagnosis method, including the following steps: sampling capacitor voltages of submodules (SM), constructing an isolation tree (IT) according to capacitor voltage data, and calculating a depth of each SM in the IT; and forming an IF based on the ITs, calculating average depths of the SMs in the IF, taking an SM with the minimum average depth as an output of the IT, and finally locating a faulty SM by an output buffer to realize accurate location of the faulty SM. Only capacitor voltages of SMs are involved, and no extra hardware resources are required. System parameters are not involved, construction of a system mathematical model and manual setting of an empirical threshold are not required, and the robustness is high. Faults are located using sparsity and difference of abnormal data based on unsupervised learning, mass data analysis and sample training are not required, and the method has the advantages of linear time complexity, small data volume, simple calculation process, low calculation cost, and the like.

Claims10

Dependent claims

An isolation forest (IF)-based modular multilevel converter (MMC) open-circuit (OC) fault diagnosis method, comprising the following steps:

step 1:
sampling an infinite flow signal of a capacitor voltage of an MMC over time at a sampling frequency of fs and a sampling interval of Ts;
step 2:
constructing, based on capacitor voltage data sampled at each time, an isolation tree (IT) for the capacitor voltage data of a bridge arm;
step 3:
calculating a depth D(i) of each submodule (SM) SMi in the IT based on the constructed IT;
step 4:
taking Ts as one sampling time, forming an IF based on m ITs constructed at m consecutive sampling times, and calculating an average depth AD(i) of each SM SMi in the IF;
step 5:
denoting a serial number i of an SM with a minimum average depth AD(i) in the IF, serving as a current output of the IF, as an IFO, and orderly storing in an output buffer capable of accommodating k IFOs;
and
step 6:
outputting an SM fault location flag Flag according to a condition of the output buffer, and determining whether there is a fault.

10 more elements

Dependencies are inferred from the claim text.

Isolation forest-based modular multilevel converter open-circuit fault diagnosis method devices

Life of this patent

Isolation forest-based modular multilevel converter open-circuit fault diagnosis method devices

Life of this patent

Abstract

Claims10