Grid-Side Harmonic Current Suppression Based on Carrier Phase-Shifted PWM and Extended State Observer for High-Power Multiple Parallel 3L-ANPC Rectifier

In the high-speed maglev system, high-power multiple three-level active neutral point clamped rectifiers are connected in parallel to the grid via phase-shifting transformers. Due to the low switching frequency and long dead time, the rectifiers produce rich low-order harmonics, which will deteriorate the power quality. In this article, harmonic current suppression strategies based on improved carrier phase-shifted (CPS) PWM and the extended state observer (ESO) are proposed. Aiming at the minimum total harmonic distortion of the grid-side current, the universal guidelines for the optimal CPS angle with the number of rectifiers are proposed. To suppress the low-order harmonics, multiresonance controllers are introduced into the disturbance estimation loop of the ESO, whose output is used for feed-forward compensation. The effectiveness of the strategies is verified by hardware-in-the-loop simulation and experiments.