Multi-carrier based hysteresis current control technique for five-level symmetric cascaded multilevel converter

Abstract

Hysteresis current control (HCC) based voltage source converters (VSCs) have several advantages like good dynamic response, over-current protection, insensitive to load parameter variation and ease of implementation. The application of HCC technique for two-level VSCs are well established and few modifications of the same are also reported to operate with variable or constant switching frequency in case of multilevel converters. In this paper, a multi-carrier based HCC technique is proposed for five-level symmetric cascaded multilevel converters for precise current tracking, good output voltage profile, and reduced implementation complexity. The proposed technique is explained for single-phase five-level symmetric cascaded converter using hybrid phase-shifted triangular carriers. The same is extended for three-phase five-level symmetric cascaded converter system with control implemented in synchronously rotating d-q reference frame. The simulation results thus obtained in MATLAB/Simulink environment are presented and analysed to evaluate the performance of the proposed current control strategy.