Switching State Sequences-Based Modulation Scheme for T-Type 5L-ANPC Converter

Kun Wang,Yong Yang,Yingfei Xu,Yi Lu,Guangdi Li,Yan Deng,Xiangning He

doi:10.1109/access.2019.2930974

Abstract

A switching state sequences (SSSs)-based modulation scheme along with a dead-time effect compensation method is proposed in this paper. In the proposed modulation scheme, the converter’s switching states changing sequence in one carrier period, i.e., the SSS, is treated as the basic unit to control the T-type 5L-ANPC converter. Because there are only two possible voltage levels in each SSS, the converter can be controlled as a traditional two-level converter within each SSS. Thus, a switching pulse modification-based method is proposed to compensate the dead-time effect within each SSS. Moreover, an SSS transition rule and the transition diagram are furtherly presented to avoid the dead-time effect between different SSSs. Consequently, both the output voltage delay and the unwanted voltage glitches that caused by the dead-time effect are avoided in the whole modulation range. Besides, a balancing strategy is proposed to balance the flying capacitor voltage based on the charging abilities of SSSs. The performance and effectiveness of the proposed modulation scheme are validated by both simulation and experimental results.

Highlights

INTRODUCTIONIn [18], a space vector PWM (SV-PWM) method is proposed for the 5L-active neutral point clamped (ANPC) converter, where the dead-time effect is compensated by selecting proper vector sequences and constraining the switching states transitions
Multilevel converters have received increased attention in medium- and high-power conversion systems due toThe associate editor coordinating the review of this manuscript and approving it for publication was Alexander Micallef.the lower total harmonic distortion (THD) and higher efficiency [1]–[8]
There are three types of multilevel converter topologies that widely used in industry, i.e. the neutral point clamped (NPC) converters [4], [5], flying capacitor (FC) clamped converters [6], [7] and cascaded H-bridge (CHB) converters [8]

Summary

INTRODUCTION

In [18], a space vector PWM (SV-PWM) method is proposed for the 5L-ANPC converter, where the dead-time effect is compensated by selecting proper vector sequences and constraining the switching states transitions. Taking dead-time effect compensation into consideration, the modulation reference generation for each switch and the SSS transition rules are furtherly introduced . DEAD-TIME EFFECT COMPENSATION As presented, there are 16 kinds of switching state commutation modes in the SSSs based modulation scheme. A. DEAD-TIME EFFECT COMPENSATION WITHIN SSSs Since the switching states transitions are mapped to the ON/OFF control of eight switches, the 5L-ANPC converter can be controlled as a two-level converter in each SSS. Since the compensation method above can only deal with dead-time effect inside the SSSs, an SSS transition rule is furtherly proposed for this situation. While the actual transition paths are influenced by the requirement of FC voltage balancing control as analyzed

BALANCING STRATEGY OF THE FLYING CAPACITOR

SIMULATIONS AND EXPERIMENTAL VALIDATION

Findings

CONCLUSION