Online Estimation of DC-Link Capacitance for Permanent Magnet Synchronous Motor Drive with Reduced DC-Link Capacitor

In order to avoid the failure of electrolytic capacitor due to the influence of ambient temperature, film capacitors are applied in the DC-link of permanent magnet synchronous motor (PMSM) drive systems. In this paper, an online estimation method of DC-link capacitance is proposed for the electrolytic capacitorless motor drive system. The power signals of the drive system are analyzed, and the characteristic frequency of the DC-link capacitance power is determined. The instantaneous capacitor power is obtained by the sampled grid input power and the reconstructed inverter power, which is determined by the DC-link voltage and inverter input current. The components of capacitor power and the result of multiplication of DC-link voltage and its derivative at the expected frequency are obtained to calculate the DC-link capacitance by a band-pass filter. The estimation process can be carried out when the system operates normally, and no additional sensors are required. The experimental results verify the effectiveness of the proposed method.