Condition Monitoring of a DC-Link Capacitor Using the Instantaneous Output Power of a Propulsion Inverter with One-Pulse Modulation

Condition-based maintenance (CBM) is an effective approach for ensuring the safe operation of power electronic converters used in industrial applications, grid-tied ones, and transportation systems. This paper proposes a condition-monitoring method of a DC-link capacitor used in a propulsion inverter for a rolling stock, where capacitance is used as the indicator of its degradation. This method utilizes the instantaneous output power of the inverter to reproduce the ripple current of the dc-link capacitor, which allows current-sensor-less condition monitoring of the dc-link capacitor. In addition, the capacitor voltage is obtained from a sampled one synchronized to a multiple of the carrier frequency available in a practical propulsion inverter. A 200-V 1.5-kWlaboratory system with an induction motor is designed and constructed for emulating the propulsion inverter with synchronous pulse-width modulation in a region with constant output power. Experimental results confirmed that the capacitance of the dc-link capacitor was monitored from the sampled voltage and reproduced ripple current with the proposed method.