Mitigating Deadtime Nonlinear Effect in SVPWM Using Variable DC-Link Voltage for High Switching Frequency SiC Motor Drives

The concept of this study is to set the DC bus voltage of the motor drive circuit as a control factor and explore the appropriate driving conditions for the motor control system using the space vector pulse width modulation method. The wide power range and fast switching capability of SiC MOSFETs expand motor drive capabilities. However, if the motor is designed for a wide operating range, driving with a high DC voltage at low speed may cause severe deadtime effects and excessive zero vectors, resulting in current harmonics and reduced efficiency. To find the appropriate motor driving conditions, this study derived the relationship between switching frequency and deadtime, and analyzed the formula between DC bus voltage and flux ripple that effect total harmonic distortion of current. Through a motor drive load experiment with an appropriate switching frequency, a buck converter is used to step down the DC bus voltage, reduce the deadtime ratio, and thus reduce the total harmonic distortion of the current. It is proved that reducing the DC bus voltage can suppress the total harmonic distortion of the three-phase current and torque ripple, thereby improving the system efficiency.