Decoupled space vector modulation model and maximum modulation index analysis for nine-switch converters

Abstract

Nine-switch converter (NSC) has been developed as a compact solution for dual-output applications, but its switch-sharing architecture introduces inherent coupling problems between output ports that poses modulation difficulties. This article establishes a decoupled space vector modulation (SVM) model for NSC to address this fundamental challenge. Through analytical reconstruction of the conventional SVM model and decomposition of reference vectors, the proposed modeling method achieves decoupled modulation and independent port control while reducing the complexity of SVM algorithm. Based on the proposed decoupled model, a comprehensive mathematical analysis of the maximum modulation index is derived and the analytical expression formula is obtained, explicitly revealing the phase-dependent linear modulation range of NSC. The performance of the proposed SVM method is validated through simulation and a 400 V, 3 kW experimental prototype and the experiment results exhibit strong agreement with the theoretical analysis of maximum modulation indices.