Online Estimation Method of the DC-Link Capacitance Based on Impedance Analysis for PMSM Drives

Electrolytic capacitors are usually most seriously affected by aging in power electronic systems and it is necessary to timely indicate the degradation status of the electrolytic capacitor for ensuring the safe operation of the system. An online estimation method of the DC-link capacitance based on impedance analysis for permanent magnet synchro-nous motor (PMSM) drives with the boost power factor correction (PFC) converter is proposed, which does not need any additional signal injection or DC-link capacitor current sensor. Based on the principle of area equivalence, the capacitor current can be reconstructed by the inductor current and the duty ratio in the boost PFC converter. The bandpass filter (BPF) is applied to extract the 100Hz ripples from DC-link voltage and capacitor current. Through analyzing the capacitor impedance characteristics, the DC-link capacitance can be estimated by the 100Hz ripple voltage and the 100Hz ripple current. The experimental results verified the effectiveness of the estimation method.