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Fault Detection Methods for Three-Level NPC Inverter Based on DC-Bus Electromagnetic Signatures

This paper proposes two new open-circuit fault detection methods suitable for the diagnosis of power electronics converters. The faulty semiconductor devices are identified using conducted and radiated electromagnetic signatures of the dc bus through nonintrusive measurements. The first method uses a low-cost electromagnetic interference filter to collect the common-mode emissions signature. The second one utilizes an external antenna to collect the emitted near-field signature. Both methods are tested on a three-level neutral point clamped inverter (NPC) inverter with the aim to identify the clamping diodes open-circuit faults. Indeed, each open-circuit fault affects the common-mode emission signature in the time-domain, while the fast Fourier transform of the emitted near-field showed substantial reduction of spectrum amplitude at a specific radio frequency range and the appearance of a new spectral rail. The effectiveness of these two methods has been tested through numerical simulations and validated by experimental results which confirmed its high performance in detecting single as well as multiple open-circuit faults for three-level NPC inverter.