Common-Mode Voltage Suppression Strategy Based on Fast MPC for a Five-Level Nested Neutral Point Piloted Converter

This paper, regarding a five-level nested neutral point piloted (NNPP) converter as the research object, analyzes the working mechanism of an NNPP five-level converter and determines the switching commutation circuit and switching principles. To solve the problem of common-mode voltage (CMV) in NNPP five-level converters, a control strategy based on fast model predictive control (MPC) is proposed to effectively suppress common-mode voltage. The control method proposed in this paper is divided into two main parts. First, 19 zero common-mode voltage (ZCMV) vectors are selected from 125 voltage vectors, and 19 ZCMV vectors are optimized to select the best ZCMV vector. Next, according to the switching principles, the effective switching combinations are selected as the effective candidate control set, and proper switching combinations of the optimal ZCMV vector are determined. The effectiveness and validity of the proposed suppression strategy based on fast MPC in terms of the steady state and dynamic performance is confirmed by simulation and experimental results of the five-level NNPP converter.