Torque Ripple Reduction of Electrolytic Capacitor-less BLDC Motor Drive using Simultaneous Speed and Torque Control (in Persian)

Abstract

Nowadays, optimum energy consumption and increasing expansion of permanent magnet motors in domestic, industrial and semi-industrial sectors have led to considerable attention to lower cost of such motors in various parts of a drive such as processors, power electronic switches, sensors and power devices. The electrolytic capacitor of DC link not only occupies a large amount of space on PCB board but also is sensitive to the generated heat by the switching elements that leads to a shorter lifetime. Moreover, lack of electrolytic capacitor causes fluctuations with twice as large as the grid frequency in DC voltage, that leads to considerable torque ripple and speed fluctuations in motor.  In order to solve this problem, this paper proposes a new method in which, by simultaneously controlling the motor speed and torque and proper switching, the electrolytic capacitor is substituted with a small ceramic capacitor in DC-bus. As a result, ceramic capacitors can be used with greater reliability than electrolytic capacitors in terms of effective lifetime. The proposed method is simulated in MATLAB software and also implemented in laboratory with XMEGA microcontroller and low-cost MOSFET and ceramic capacitor with simple control topology to prove the validity of the proposed strategy.