A General Low-Frequency Zero-Sequence Circulating Current Suppression Approach for Coordinated PWM Schemes in Two-Parallel Three-Phase Two-Level Power Converters

This article addresses the challenge of mitigating low-frequency circulating currents caused by imbalanced inductance while preserving the inherent benefits of coordinated pulsewidth modulation (PWM) schemes. The analysis reveals that traditional common-mode injection is incompatible with the coordinated PWM schemes. To resolve this, this article proposes a general approach to suppress the low-frequency circulating current for the coordinated PWM schemes. Unlike the traditional common-mode signal injection, the proposed method features the different-mode signal injection into different phases at specific vector angles. The proposed method preserves the intricate vector sequences of coordinated PWM schemes, maintaining their original benefits. Moreover, a comprehensive control model and structure are developed to support differential-mode signal injection. Finally, two typical coordinated PWM schemes were chosen as case studies, covering both clamping and nonclamping methods. The proposed method was applied to these schemes to suppress low-frequency circulating currents, and the effectiveness was validated through testing on a prototype. Experimental results confirm that the proposed method effectively suppresses low-frequency circulating currents while retaining the performance characteristics of the original PWM schemes. This article is a progressive extension of the existing coordinated PWM schemes to enhance their practical applicability.

Duke Scholars

Author Stefan M Goetz Psychiatry & Behavioral Sciences, Behavioral Medicine & Neur ...