An Online Estimation Method for DC-Link Capacitor in Doubly Salient Electromagnetic Motor Drive System

As a key component of the motor drive system, the dc-link capacitor has a significant impact on the system reliability. Therefore, it is of great significance to monitor the health status of the capacitor to assist the drive system in achieving preventive maintenance. This article proposes an online estimation method for dc-link capacitor in doubly salient electromagnetic motor (DSEM) drive system with small dc-link capacitance. By utilizing the characteristic that energy flows back from the motor to the bus during the commutation process, causing fluctuations in dc-link capacitor voltage, this method estimates the dc-link capacitance value based on the relationship among the motor phase current, dc-link capacitor voltage, and capacitance value. The proposed method requires no signal injection or the use of additional sensors, does not affect the normal operation of the motor, and offers high-estimation accuracy. The experimental results verify the effectiveness and practicality of the proposed dc-link capacitor estimation method.