PWM frequency conversion method

The invention provides a PWM (Pulse Width Modulation) frequency conversion method, which is used for solving the problems of current jitter and torque jitter of a permanent magnet synchronous motor at a specific rotating speed, calculating whether a carrier period Tsw can cause existence of low-frequency harmonics in current or not in real time according to the current rotating speed, and if so, adjusting the carrier period until the low-frequency harmonics are eliminated. According to the invention, the carrier cycle is changed only at the rotating speed generating frequency aliasing, and the problems of three-phase current low-frequency jitter and torque low-frequency jitter at the specific rotating speed are solved; moreover, as the carrier cycle changes slightly, the problems of insufficient load rate, reduction of control bandwidth and the like caused by the change of the carrier cycle are solved. 本发明提供了一种PWM变频方法，用于解决永磁同步电机在特定转速下的电流抖动及扭矩抖动，根据当前转速实时计算载波周期Tsw是否会导致电流中存在低频谐波，如果存在，则调整载波周期，直至消除低频谐波。本发明只在产生频率混叠