Compensation Control Method of Asymmetric Capacitive Filter for Permanent Magnet Synchronous Motor Fed With Current-Source Inverter

Due to system faults, manufacturing imperfections, assembly tolerances, and operational conditions, the filter capacitors of current-source inverters (CSIs) for permanent magnet synchronous motor drives may be asymmetric in real systems, which results in significant torque ripples. To deal with this issue, this article first studies the influence of asymmetric capacitive filters on torque ripples and then proposes three compensation control schemes. Based on the phasor method, the motor currents under asymmetric capacitive filters are first obtained. Then, the torque ripples can be reduced by eliminating the negative-sequence currents (NSCs), which can be achieved by PI controller (NSC-PI), the calculating compensation matrices (NSC-CM-Calculation), and the measuring compensation matrices (NSC-CM-Measured). The control scheme based on NSC-CM-Measured has the best compensation performance among these three methods. However, it requires the measurement of compensation coefficients and d- and q-Axis currents caused by back electromotive forces (back EMFs). It shows that the control scheme based on NSC-CM-Calculation has good compensation performance and fast dynamic performance and can be extended to other asymmetric conditions easily, such as open-circuit filter capacitor conditions. Finally, the experimental results have verified the effectiveness of the proposed compensation schemes.