Online estimation method of DC-link capacitors for reduced DC-link capacitance IPMSM Drives

In this project, In order to extend the lifetime and save the system cost, the film capacitor is applied in the DC-link of IPMSM drives. Many active damping control methods have been carried out to improve the drive system stability, which need the accurate value of the DC-link film capacitor. In this letter, an online DC-link capacitance estimation method is investigated for reduced capacitance IPMSM drives, which does not need any additional signal injection or sensor. 

The power coupling characteristics are analyzed to obtain the instantaneous power of the DC-link capacitor from the inverter and the grid sides. The band-pass filter is applied to extract the DC-link voltage and capacitor power with twice the frequency of the grid voltage. The DC-link capacitance could be estimated by the fundamental component of the DC-link voltage. The proposed method can be used for different kinds of load types and motor types of the drive system. Experimental results are performed to verify the estimation method, and the estimation error is within 1%.

Keywords: Online capacitance estimation, Motor drive, Online capacitance estimation, Reduced DC-link capacitance