An on-line DC-link Capacitance Estimation method for Motor Drive System Based on Intermittent Active Control Strategy

The condition monitoring of the direct-current (DC)-link capacitors is critical for operating reliability of the inverter-based motor drive system. Therefore, in industry applications, reliable preventive maintenance of the power electronics devices in motor drive systems is required. The previous proposed DC-link capacitance monitoring technologies are inadaptable for applications due to the required specific conditions, algorithm complexity and high cost. In this paper, an on-line estimation method for DC-link capacitance in motor drive system is proposed. This method is based on the intermittent ON-OFF control strategy, which provides a specific discharging circuit for the DC-link capacitor bank. The discharging current is the current of a specified phase, which is measurable in typical system. The normal discharging stage of the DC-link capacitors is actively modified, and the transient process is used for the on-line estimation of the DC-link capacitance. Verification of the proposed method are implemented based on simulation and experimental tests. The advantages of the proposed method are the normal operation monitoring capability and no additional sensor requirement.