A Quasi-Three-Level PWM Modulation Method with Suppressed Coil Terminal Overvoltage for Active Magnetic Bearing

Switching power amplifier is one of the vital actuators of active magnetic bearing (AMB), which directly determine the bandwidth of AMB. As higher DC bus voltage and faster switching speed both contribute to the dynamic performance of a power amplifier, the application silicon carbon (SiC) devices, which is to substitute the inadequate silicon (Si) ones, become more and more popular. However, the high voltage change rate (dv/dt) brought by the high switching speed of SiC devices leads to serious overvoltage at the load coil terminal when the SiC half-bridge switching power amplifier drives the load coil, this brings risks to the insulation reliability of the transmission cable and the load inductance coil. In this paper, the reasons for the overvoltage of the load coil terminal are analyzed. Then, according to the overvoltage generation mechanism of the SiC half-bridge switching power amplifier, a quasi-three-level PWM modulation overvoltage suppression algorithm is proposed, which effectively suppress the overvoltage at the load coil terminal. Finally, an experimental platform is built to verify the effectiveness of the proposed method.