Hybrid‐Frequency Power Loop to Eliminate Negative‐Sequence Current for Star‐Connected Cascaded H‐Bridge STATCOM

ABSTRACT Since the power grid frequently experiences asymmetric operation caused by the unbalanced power load, the current compensation for the negative‐sequence component is typically required to control the star‐connected cascaded H‐bridge STATCOM. However, the compensation range of the negative‐sequence current injection is usually limited. This paper proposes a novel STATCOM topology by adding an interphase high‐frequency power loop to extend the compensation range. It only adds two groups of RLC resonators, upon which the extra high‐frequency resonant voltage is injected to transfer and redistribute power among the three phases. A control strategy considering the hybrid‐frequency power loop is further proposed by analysing the proposed working principle of the proposed structure. In addition, comprehensive quantitative assessments, including the compensation capability for the negative‐sequence current, the added volume/weight, and system efficiency, are conducted and compared. Finally, the comparative experimental results verify the effectiveness of the proposed analysis and method.