Current Harmonic Analysis of Fundamental Frequency Isolated Three-phase PWM Rectifier Using DPWM

Under high power and large current conditions, the switching frequency of three-phase PWM rectifiers is relatively low, and the inductance value is small. To prevent circulating currents from affecting control stability, a power supply scheme utilizing fundamental frequency transformer with parallel branches can be adopted. This paper analyzes the current harmonics of the discontinuous pulse width modulation (DPWM) strategy under different transformer connection groups and carrier phase-shifted angles. With the increase in switching frequency, the optimization of current harmonics under dual-branch and carrier phase-shifted conditions surpasses that under single-branch condition. A 6 MW fundamental frequency isolated dual-parallel three-phase PWM rectifier is modeled in MATLAB for simulation verification, and the simulation results align well with the theoretical analysis.