Abstract：Multi-phase interleaved parallel Buck converters are susceptible to compound open-circuit faults (simultaneous failures in two or more phases) under high-intensity operating conditions. However, existing fault diagnosis methods utilizing inductive current observers can determine the number of faulty phases but encounter difficulties in accurately isolating multi-phase fault information from coupled outputs, especially under load uncertainty, which often leads to misdiagnosis and missed faults. This paper proposes a compound open-circuit fault diagnosis method for multi-phase Buck converters based on an unknown fault input observer (UFIO). A three-phase interleaved parallel Buck converter serves as the research object, where output voltage and load current are sampled, and the UFIO is employed to achieve decoupling and reconstruction of each phase's inductor current. First, the converter's fault model is established, incorporating both power device faults and load uncertainty. Next, precise separation of each phase's inductor current information is accomplished through scenario-specific observer gain matrix design. Finally, adaptive load parameter estimation enables the recon- struction of per-phase inductor currents, facilitating subsequent fault detection and identification. The simulation results demonstrate that the proposed observer accurately and efficiently tracks variations in the system state during both power transients and steady-state operation. Experimental validation is performed under three distinct scenarios, including no fault, single open-circuit fault (OCF2), and compound open-circuit fault (OCF23), with load jump conditions employed to assess diagnostic performance across different fault conditions. The experimental results indicate that the diagnostic results are free from false alarms under normal conditions. The single open-circuit fault flag is accurately set within two switching cycles (approximately 35 μs) after the occurrence of OCF2. Additionally, the composite open-circuit fault flag is accurately set within two switching cycles (approximately 38.4 μs) after the occurrence of OCF23, with no misdiagnosis in any other fault flags. Further comparison reveals that the OCF23 diagnosis time is approximately 37.7 μs without considering load adaptation, and there is a time difference of 0.7 μs compared with 38.4 μs considering load adaptation, which has a marginal impact on the overall rapidity of fault diagnosis. Although the introduction of load parameter adaptation slightly increases diagnosis time, it effectively addresses the issues of fault leakage and misdiagnosis caused by power transients, thereby improving diagnosis accuracy. The simulation and experimental results show that: (1) The proposed fault diagnosis method utilizes the UFIO to reconstruct per-phase inductor currents, achieving the dynamic tracking of the inductor current state under uncertain load changes and input voltage fluctuations. (2) The proposed fault diagnosis method localizes the single open-circuit faults and composite open-circuit faults under the variable-load condition in less than two switching cycles. (3) The proposed fault diagnosis method is based on the design of system model construction and observer decoupling, which can be extended to other power electronic topology objects.
卢伟国, 何晴, 白月, 马乐, 张淮清. 多相Buck变换器功率器件复合开路故障诊断方法[J]. 电工技术学报, 2025, 40(24): 8080-8092.
Lu Weiguo, He Qing, Bai Yue, Ma Le, Zhang Huaiqing. Converter Compound Open Circuit Fault Diagnosis Method for Power Devices of Multi-Phase Buck Converter. Transactions of China Electrotechnical Society, 2025, 40(24): 8080-8092.
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