A universal and new harmonic algorithm of voltage and current of permanent magnet synchronous motors supplied by PWM inverter

According to the working principle of PWM inverter circuit and the characteristic of permanent magnet synchronous motors (PMSM), a new and versatile algorithm considering the actual switching device characteristics was proposed, which was applied in the harmonic calculation of PMSM voltage and current. The mathematical relation was analyzed between on-off time and the fundamental period of the PWM waveform and modulation method and mode of the PWM inverter circuit, and the expressions of PMSM voltage harmonics were derived. Secondly, combining with the type of load and control strategy, the calculation formula of PMSM current harmonics were also deduced. In order to validate the algorithm, Matlab/SIMULINK simulation model and experimental device platform of the motor and control system were built, and related simulation and experiments was made. Taking the discreteness of simulated data and measured data into account, the discrete Fourier transform (DFT) was introduced. The DFT were compared with simulation and experiment, they have better agreement, and the validity of the theoretical analysis was proved. The algorithm flow is clear and simple, and it is still practical.