Stability analysis and duty cycle limitation of grid‐connected current control strategy for multiple parallel three‐level T‐type grid‐connected inverters

Abstract

Multiple parallel three‐level T‐type inverters (3LT2Is) have become the trend in large‐power low‐voltage applications. In parallel operation of modular 3LT2Is, three aspects including current sharing control, circulating current suppression and neutral‐point potential (NPP) balance control should be considered. In this study, a grid‐connected current control strategy with the ability to independently adjust three control objectives is proposed for the multiple parallel three‐level T‐type grid‐connected inverters. The duty cycle limitation among current sharing, NPP balancing and circulating current and their influence are analysed in detail. The stability analysis of multi‐paralleled inverters on the basis of the single‐phase equivalent circuit is carried out considering the influence of circulating current. Experimental results prove the validity of the proposed control strategy.