Search Results (4)

DFIG rotor windings face high stress and transients from back-to-back converters, causing inter-turn short circuit (ITSC) faults. Rapid rotor-side dynamics, combined with the unique capability of DFIG to operate in multiple modes, make the fault detection in rotor windings more challenging. This paper presents a comprehensive methodology for online ITSC fault diagnosis in DFIG rotor windings based on zero-sequence current (ZSC) component analysis under variable operating conditions. Fault features are identified and defined through the analytical evaluation of the DFIG mathematical model. Further, a simple yet effective algorithm is presented for online implementation of the proposed methodology. Finally, the simulation of the DFIG model is carried out in MATLAB/Simulink under both sub-synchronous and super-synchronous modes, covering a range of variable loads and low-frequency conditions, along with different fault severity levels of ITSC in rotor windings. Simulation results confirm the effectiveness of the proposed methodology for online ITSC fault detection at a low-severity stage and precise location identification of the faulty phase within the DFIG rotor windings under both sub-synchronous and super-synchronous modes. Full article

The series-winding permanent-magnet synchronous motor (SW-PMSM) has the merits of high output power and excellent control performance, as does the open-winding permanent-magnet synchronous motor (OW-PMSM). Meanwhile, it can greatly reduce the number of power devices. However, due to the existence of the zero-sequence path, zero-sequence current occurs, which can cause additional losses and torque ripples. Thus, this paper proposes a novel direct torque-control strategy for the SW-PMSM with zero-sequence current suppression capability (ZSCS-DTC). First, the series-winding topology (SWT) and the voltage vector distribution in the SW-PMSM drives are analyzed. Secondly, the basic DTC (B-DTC) scheme for the SW-PMSM is investigated, and the defects of zero-sequence current open-loop control in the B-DTC scheme are revealed. Thirdly, a new voltage vector synthesis scheme is proposed for suppression of zero-sequence current while ensuring bus voltage utilization. A switching table is reconstructed with the newly synthesized voltage vectors. On this basis, a ZSCS-DTC scheme for the SW-PMSM is proposed based on zero-sequence current closed-loop control so that electromagnetic torque, stator flux linkage and zero-sequence current can be controlled simultaneously. Finally, the effectiveness of the proposed ZSCS-DTC scheme for the SW-PMSM drives is verified. Full article

At present, the small resistance to ground system (SRGS) is mainly protected by fixed-time zero-sequence overcurrent protection, but its ability to detect transition resistance is only about 100 Ω, which is unable to detect single-phase high resistance grounding fault (SPHIF). This paper analyzes the zero-sequence characteristics of SPHIF for SRGS and proposes a SPHIF feeder detection method that uses the current–voltage phase difference. The proposed method is as follows: first, the zero-sequence current phase of each feeder is calculated. Second, the phase voltage root mean square (RMS) value is used to determine the fault phase and obtain its initial phase as the reference value. The introduction of the initial phase of the fault phase voltage can highlight the fault characteristics and improve the sensitivity and reliability of feeder detection, and then CVPD is the difference between each feeder ZSC phase and the reference value. Finally, the magnitude of CVPD is judged. If the CVPD of a particular feeder meets the condition, the feeder is detected as the faulted feeder. Combining the theoretical and practical constraints, the specific adjustment principle and feeder detection logic are given. A large number of simulations show that the proposed method can be successfully detected under the conditions of 5000 Ω transition resistance, –1 dB noise interference, and 40% data missing. Compared with existing methods, the proposed method uses phase voltages that are easy to measure to construct SPHIF feeder detection criteria, without adding additional measurement and communication devices, and can quickly achieve local isolation of SPHIF with better sensitivity, reliability, and immunity to interference. Full article

This paper presents some considerations regarding the application of the stator zero-sequence current component (ZSC) in the fault detection of cage induction machines, including the effects of magnetic core saturation. Faults such as rotor cage asymmetry and static, dynamic, and mixed eccentricity were considered. The research started by developing a harmonic motor model, which allowed us to obtain a voltage equation for the zero-sequence current component. The equation allowed us to extract formulas of typical frequencies for particular fault types. Next, in order to verify the effectiveness of ZSC in induction motor fault diagnosis, finite element calculations and laboratory tests were carried out for the previously mentioned faults for delta and wye connections with neutral wire stator winding configurations. Full article