Modeling and Control of the Three-Phase NPC Multilevel Converter using an Equivalent Matrix Structure

Abstract

This paper presents a modeling and control of three-phase NPC (Neutral Point Clamped) n-level converter. First, the equivalent matrix structure of the NPC n-level converter is developed. Therefore the relation between the 3×(n-1) switching functions of the matrix converter and the gate signals of transistors of the NPC n-level converter are given. Then, a line-to-line Space Vector Modulation (SVM) strategy for a three-phase matrix inverter is used to obtain the switching function. Finally the gate signals of the three phase NPC multilevel converter can be calculated by inversing the modeling parts. In this work, the direct space vector multilevel modulation which is based on the use of 2n different three-level functions called modulation functions is presented. Using this approach, a modulation strategy of a three phase NPC converter is designed without using a Parks transform. To highlight the effectiveness of this control system, a simulation results are given for a three-phase five-level NPC converter.