Eccentricity fault detection in brushless doubly fed induction machines

Mojtaba Afshar,Salman Abdi,Mohammad Ebrahimi,Richard Mcmahon,Ashknaz Oraee

doi:10.1049/elp2.12060

Abstract

A new fault diagnosis method for detecting the rotor eccentricity faults including static, dynamic and mixed eccentricity is proposed for brushless doubly-fed induction machines (BDFIMs). BDFIMs are attractive alternatives for the conventional doubly-fed induction generator (DFIG) for offshore wind power generation; therefore, paying attention to their fault detection is essential. Existing fault detection methods for conventional induction machines cannot be directly applied to the BDFIM due to its special rotor structure and stator winding configurations as well as complex magnetic field patterns. This article proposes a novel fault detection method based on motor current signal analysis to determine stator current harmonics, induced by the nested-loop rotor slot harmonics (NRSHs), as fault indices. The analysis is performed under healthy conditions and with different types of rotor eccentricity. Finally, a sensitivity analysis is carried out to confirm the practicability of the proposed technique with various fault intensities and load conditions. Analytical winding function approach, finite element analysis and experimental tests on a prototype D180 BDFIM are used in this study to validate the proposed fault detection technique.

Highlights

The brushless doubly‐fed induction machine (BDFIM) is an alternative to the well‐established doubly‐fed induction generator (DFIG) for use in wind turbines since it offers improved reliability and reduced capital and maintenance costs [1]
A novel analytical method is proposed for the BDFIM to determine time harmonic frequencies induced in stator winding currents by the nested‐loop rotor slot harmonics (NRSHs) when the rotor is centric and different types of rotor eccentricity are presented
The power winding (PW) currents of the prototype BDFIM are obtained under dynamic eccentricity (DE) fault conditions and under 20% of fault intensity using winding function method and finite element (FE) analysis

Summary

| INTRODUCTION

The brushless doubly‐fed induction machine (BDFIM) is an alternative to the well‐established doubly‐fed induction generator (DFIG) for use in wind turbines since it offers improved reliability and reduced capital and maintenance costs [1]. A novel analytical method is proposed for the BDFIM to determine time harmonic frequencies induced in stator winding currents by the nested‐loop rotor slot harmonics (NRSHs) when the rotor is centric and different types of rotor eccentricity are presented. The proposed method is validated using an analytical winding function approach and finite element (FE) analysis for a D180 BDFIM operating in synchronous mode under rotor centric and eccentric conditions. A winding function model has been developed for the D180 BDFIM, using which all the PW and CW inductances can be calculated under healthy and rotor eccentricity conditions. A new MCSA‐based method is proposed to detect eccentricity faults in BDFIMs. The BDFIM airgap magnetic field is analytically obtained for the case of centric rotor as well as different types of rotor eccentricity and the NRSHs are. Using Equations (5) and (9), and θr 1⁄4 θs − ωrt, the rotor airgap flux in the stator reference frame can be calculated as:

A pp kN n θs ð12Þ

Findings

| CONCLUSIONS