Aug 2026· IEEE Transactions on Circuits and Systems Part 1: Regular Papers· Vol 73, pp. 5725-5738· 0 citations· 22 references
Abstract
The safety and reliability of inverters are crucial for the stable operation of the entire system, making accurate and effective OC (open-circuit) fault diagnosis methods particularly essential. This paper proposes an OC fault diagnosis strategy for three-level T-type inverters based on voltage vector trajectory centroid deviation characteristics. By analyzing the spatial distribution characteristics of the output voltage vector trajectory after an OC fault, it is found that the trajectory centroid undergoes varying degrees of displacement when a single-switch OC fault occurs. The magnitude and phase characteristics of the vector from the origin to the displaced centroid can be utilized to identify different single-switch OC faults. For double-switch combined faults, the centroid deviation vector can be equivalently characterized by the linear superposition of single-switch fault vectors. The centroid deviation vector features enable the identification of fault types where the vector is non-zero. Furthermore, the centroid vector characteristics of the first-quadrant trajectory can distinguish double-switch faults where the centroid vector is ac zero vector. The proposed method can diagnose single-switch faults and arbitrary double-switch combined faults in any phase. The diagnostic algorithm features low computational complexity and fast diagnosis speed, effectively addressing the issue of load sensitivity in conventional diagnosis methods.
Three-level neutral-point-clamped (NPC) inverters are widely used in medium- and high-power drives and grid-connected applications due to their reduced device voltage stress, improved output power quality, and lower switching losses relative to conventional two-level topologies. Among the potential failure modes, clamping diode open-circuit faults are difficult to detect because the clamping diodes conduct only during the zero-voltage states, and their failure produces only subtle distortions in the phase current waveform. This paper proposes a fault diagnosis method for clamping diode open-circuit faults in three-level NPC inverters. The method is based on a current asymmetry index defined as the ratio of the per-cycle mean phase current to the per-cycle mean absolute phase current. During healthy operation, this index is approximately zero in all phases. A fault causes the index to deviate markedly from zero, while the polarity of this deviation identifies the failed diode. The method requires only phase-current measurements already available in the inverter control system. Consequently, no additional sensors, hardware modifications, or changes to inverter operation are required. Simulation results obtained for a 10 kW three-level NPC inverter demonstrate successful fault detection within approximately one to two fundamental cycles for open-circuit failures of both the upper and lower clamping diodes in all three phases.
To Anh Dung, Minh Huu Nguyen, Chuong Trong Trinh et al.· Engineer· 0 citations
An ensemble subspace k-nearest neighbour model for fault detection and classification of switch open-circuit and short-circuit faults and indicates that the proposed model provides an effective and computationally efficient solution for reliable fault diagnosis in electric vehicle motor drive systems.
Masadi Prashanth Kumar, Srikanth Velpula, Chidurala Saiprakash· Transactions of the Institut...· 0 citations
In recent years, high penetrations of inverter-based resources are posing significant challenges to the medium-voltage networks, in which protection schemes based on high fault currents and unidirectional power flow may not perform as expected. This paper proposes a dynamic fault-detection and relay-coordination scheme for a medium-voltage network with high penetration of grid-forming inverter sources. A detailed 33 kV system model comprising six battery energy storage system (BESS) feeders and a four-distributed-load model was built in DIgSILENT Power Factory and tested under various grid-connected and islanded system conditions using the complete short-circuit method. Four simultaneous fault checks, including sequence component analysis, symmetrical voltage variation, superimposed current with voltage restraint, and current waveform analysis, are used to detect the fault in a specific part of the medium-voltage network. After-fault detection, dynamic pickup scaling and relay blocking are coordinated through IEC 61850 GOOSE and DNP3 so only the closest unblocked relay or relay pair trips. The dynamic pickup settings are adjusted considering the ratio of fault levels in the conventional system versus the inverter-based resources-fed medium-voltage system. Simulation results show successful overcurrent coordination retention even when inverter fault current limitation is set at 1.3 p.u. or lower with 10% generation margin. The proposed scheme allows traditional relays with existing infrastructure to function correctly in fully inverter-dominated medium-voltage systems without any synchronous backup. The novelty is the integration of fault confirmation, pickup scaling and a blocking scheme with retention of an independently operating local backup. Compared to fixed grid-connected settings, the proposed scheme recovers islanded-mode pickup values while maintaining primary–backup grading margin for the relay.
Muhammad Abdul Rauf, Munira Batool, I. Madni· Energies· 0 citations
When a short-circuit fault occurs along the transmission line of a modular multilevel converter high-voltage direct-current (MMC-HVDC) grid, the sub-module capacitors discharge, causing the fault current to rapidly rise, posing a threat to the safe operation of the system. Therefore, this paper proposes a novel fault location method based on the Gram Angle Difference Field (GADF). The column corresponding to the maximum differential value in a sliding window is used to identify the fault moment and locate faults in MMC-HVDC transmission lines. In order to effectively distinguish normal fluctuations from fault mutations and avoid false alarms, a dynamic threshold is set based on the statistical characteristics of normal data. This method utilizes the unique feature extraction capability of the GADF matrix, the adaptive mechanism of the dynamic threshold, and the stability of line-mode voltage to achieve fast and accurate fault location. Finally, this method is validated using a simulation model. The results show that the proposed method can accurately locate faults in different conditions.
Xiangyang Liu, Zhong Tang, Hong Qian et al.· Energies· 0 citations
To address the difficulty in accurately characterizing the fault current response of renewable energy grid-connected devices during high-/low-voltage ride-through, this paper proposes a fault current response modeling and parameter identification method based on adaptive nonlinear compensation. First, with the fault voltage and pre-fault operating point as input variables, a basic quadratic equivalent model is established to describe the main variation characteristics of active and reactive currents during high-/low-voltage ride-through. Second, nonlinear compensation terms are introduced into the basic model to correct the response deviation caused by the simplification of fast electromagnetic control links in the electromechanical transient equivalent process, thereby improving the representation capability of the model for complex fault current characteristics. Furthermore, considering that the structural parameters of the nonlinear compensation terms are difficult to directly identify using the traditional least squares method, a differential evolution–ridge regression (DE–Ridge) hierarchical identification method is proposed. In this method, the differential evolution algorithm is used in the outer layer to adaptively optimize the nonlinear structural parameters, while ridge regression is used in the inner layer to solve the corresponding linear coefficients. Case study results show that, compared with the traditional quadratic equivalent model and the fixed nonlinear compensation model, the proposed method further reduces the fault current identification error on the validation set and improves the identification accuracy and generalization capability of fault current responses during high-/low-voltage ride-through.
The results confirm that the proposed framework provides a comprehensive and efficient solution for real-time fault analysis by combining classification, localization, temporal analysis, and stability-aware decision support within a single model.
Nazmun Nahar Karima, M. Hazari, Shameem Ahmad et al.· Energies· 0 citations