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1. Evaluation of a Medium-Voltage Grid-Tied Cascaded H-Bridge for Energy Storage Systems Using SiC Switching Devices

   https://doi.org/10.1109/eGRID.2018.8598683  

   Mhiesan, Haider; Farnell, Chris; McCann, Roy; Mantooth, Alan (November 2018, Evaluation of a Medium-Voltage Grid-Tied Cascaded H-Bridge for Energy Storage Systems Using SiC Switching Devices)

   This paper presents the study and evaluation of a medium-voltage grid-tied cascaded H-bridge (CHB) three-phase inverter for battery energy storage systems using SiC devices as an enabling technology. The high breakdown voltage capability of SiC devices provide the advantage to significantly minimize the complexity of the CHB multilevel converter, with less power loss compared to when Silicon (Si) devices are used. The topology in this study has been selected based on high voltage SiC devices. In order to reach 13.8 kV, a nine-level CHB is needed when using 6.5 kV SiC MOSFETs. However, if 10 kV SiC MOSFETs are used, only five-levels of the CHB are required. The controls were developed, simulated and verified through an experimental prototype. The results from the scaled-down prototype proved the controls and the verification of the performance of five-level CHB three-phase inverter. For the system reliability, both open-loop and short-circuit faults are analyzed. 

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2. Adaptive Distance Protection Based on the Analytical Model of Additional Impedance for Inverter-Interfaced Renewable Power Plants During Asymmetrical Faults

   https://doi.org/10.1109/TPWRD.2021.3138128  

   Chao, Chenxu; Zheng, Xiaodong; Weng, Yang; Liu, Yu; Gao, Piao; Nengling, Tai (December 2021, IEEE Transactions on Power Delivery)

   Due to limited amplitude and controlled phase of current supplied by inverter-interfaced renewable power plants (IIRPPs), the IIRPP-side distance protection of lines connected to IIRPPs fails to detect the fault location accurately, so it may malfunction. The composite sequence network of a line connected to an IIRPP during asymmetrical faults is analyzed, and an adaptive distance protection based on the analytical model of additional impedance is proposed in this study. Based on open circuit property of negative-sequence network at the IIRPP-side, the equivalent impedance of power grid and current flowing through fault point are calculated in real-time using local measurements, which are substituted into the analytical model of additional impedance to calculate fault location. In the case of negative-sequence reactive current injection from IIRPPs during asymmetrical faults, the error of calculating fault point current from local measurements is analyzed and corrected to ensure reliability of the proposed protection. The proposed protection alleviates the effect of fault resistance in a system with weak sources. In addition, the proposed protection can adapt to different grid codes (GCs), the operation mode change of the power grid, and the capacity change of the IIRPP. PSCAD/EMTDC test results verify the effectiveness of the proposed protection. 

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3. A Robust Online Diagnostic Strategy of Inverter Open-Circuit Faults for Robotic Joint BLDC Motors

   https://doi.org/10.3390/machines12070430  

   Metwly, Mohamed Y; Logan, Victor M; Clark, Charles L; He, Jiangbiao; Xie, Biyun (July 2024, Machines)

   As robots are increasingly used in remote, safety-critical, and hazardous applications, the reliability of robots is becoming more important than ever before. Robotic arm joint motor-drive systems are vulnerable to hardware failures due to harsh operating environment in many scenarios, which may yield various joint failures and result in significant downtime costs. Targeting the most common robotic joint brushless DC (BLDC) motor-drive systems, this paper proposes a robust online diagnostic method for semiconductor faults for BLDC motor drives. The proposed fault diagnostic technique is based on the stator current signature analysis. Specifically, this paper investigates the performance of the BLDC joint motors under open-circuit faults of the inverter switches using finite element co-simulation tools. Furthermore, the proposed methodology is not only capable of detecting any open-circuit faults but also identifying faulty switches based on a knowledge table by considering various fault conditions. The robustness of the proposed technique was verified through extensive simulations under different speed and load conditions. Moreover, simulations have been carried out on a Kinova Gen-3 robot arm to verify the theoretical findings, highlighting the impacts of locked joints on the robot’s end-effector locations. Finally, experimental results are presented to corroborate the performance of the proposed fault diagnostic strategy. 

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4. Fast Detection of Open Circuit Device Faults and Fault Tolerant Operation of Stacked Multilevel Converters

   https://doi.org/10.1109/APEC.2019.8721923  

   Hekmati, Parham; Brown, Ian P.; Shen, Z. John (March 2019, 2019 IEEE Applied Power Electronics Conference and Exposition (APEC))

   This paper proposes a simple and fast technique for power device open circuit (OC) fault detection in stacked multicell converters (SMCs). A mitigation technique allowing for fault-tolerant operation using a simple front-end routing circuit is also proposed for SMCs. The fault detection concept only needs to sense the voltage and direction of current at the output terminal of the SMC to detect and localize an OC switch fault to a particular rail of the SMC. The proposed technique compares the measured and expected voltage levels considering the commanded switch states and the direction of the terminal current flow. Once an OC fault is detected and localized, the front-end routing circuit will be activated to reconfigure the SMC converter to a simple flying capacitor multilevel converter (FCMC) to maintain the output power flow with a reduced number of voltage levels. A window detector circuit is proposed to track the output voltage level and current direction with high bandwidth. Simulations were performed to validate the fault detection method and router performance. The functionality of windows detector is investigated with a hardware prototype 7 level 300 V SMC. 

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5. Leveraging Structures in Fault Diagnosis for Lithium-Ion Battery Packs

   https://doi.org/10.1109/ICPS59941.2024.10640051  

   Farakhor, Amir; Wu, Di; Wang, Yebin; Fang, Huazhen (May 2024, IEEE)

   Lithium-ion battery packs consist of a varying number of single cells, designed to meet specific application requirements for output voltage and capacity. Effective fault diagnosis in these battery packs is an essential prerequisite for ensuring their safe and reliable operation. To address this need, we introduce a novel model-based fault diagnosis approach. Our approach distinguishes itself by leveraging informative structural properties inherent in battery packs such as uniformity among the constituent cells, and sparsity of fault occurrences to enhance its fault diagnosis capabilities. The proposed approach formulates a moving horizon estimation (MHE) problem, incorporating such structural information to estimate different fault signals—specifically, internal short circuits, external short circuits, and voltage and current sensors faults. We conduct various simulations to evaluate the performance of the proposed approach under different fault types and magnitudes. The obtained results validate the proposed approach and promise effective fault diagnosis for battery packs. 

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