Space Vector Modulation with any number levels to ensure optimal switching and harmonic content in Modular multilevel converters

Abstract

This paper presents a Space Vector Modulation (SVM) method with an optimal switching process used for Modular Multilevel Converter (MMC) of any level. The proposed SVM method can produce a maximum number of levels, for example, 2N + 1, in which  N is the number of Sub-Modules (SMs) per branch of the MMC. Compared with previous modulation methods, the proposed SVM modulation method can select the closest three vectors to generate the optimal transition states, making the computation more efficient. When applying this method to the MMC, it will create the advantage which it can be applied to any number of levels without looking up the transition state table: It can create many residual states for the purpose of balancing the capacitor voltage, optimize the switching process, and improve efficiency as well as harmonic quality of the AC voltage and current. The advantages of the method are well applicable to MMC when a large number of SMs is required to converse power in high voltage systems.