Double-Carrier Phase-Disposition Pulse Width Modulation Method for Modular Multilevel Converters

Fayun Zhou,Zhixing He,Qianming Xu,Yan Li,Josep M Guerrero,An Luo

doi:10.3390/en10040581

Abstract

Modular multilevel converters (MMCs) have become one of the most attractive topologies for high-voltage and high-power applications. A double-carrier phase disposition pulse width modulation (DCPDPWM) method for MMCs is proposed in this paper. Only double triangular carriers with displacement angle are needed for DCPDPWM, one carrier for the upper arm and the other for the lower arm. Then, the theoretical analysis of DCPDPWM for MMCs is presented by using a double Fourier integral analysis method, and the Fourier series expression of phase voltage, line-to-line voltage and circulating current are deduced. Moreover, the impact of carrier displacement angle between the upper and lower arm on harmonic characteristics is revealed, and further the optimum displacement angles are specified for the circulating current harmonics cancellation scheme and output voltage harmonics minimization scheme. Finally, the proposed method and theoretical analysis are verified by simulation and experimental results.

Highlights

This paper mainly focuses on the high frequency circulating current caused by double-carrier phase disposition pulse width modulation (DCPDPWM) method for modular multilevel converters (MMCs), whereas the circulating current control method focuses on low frequency circulating currents, which can be suppressed by adding a circulating current control method [36,43]
In order to verify the validity of the DCPDPWM method and the theoretical analysis in this paper, a MMC-based three phase inverter with ten SMs per arm was developed using PSIM software
Comparison can be made between the proposed DCPDPWM method and phase-shifted carrier pulse-width modulation (PSCPWM) method presented in [43] with circulating current harmonics cancellation scheme and output voltage harmonics minimization scheme

Summary

Introduction

Modular multilevel converters (MMCs) have become one of the most attractive multilevel converter topologies available for high-voltage and high-power applications such as voltage-sourced converter high-voltage direct current (VSC-HVDC) transmission [1,2,3,4,5,6], static synchronous compensators (STATCOMs) [7], unified power flow controllers (UPFCs) [8], active power filters (APFs) [9], medium voltage motor drives [10], integration of renewable energy sources into the electrical grid [11,12,13] and battery energy storage systems [14,15]. Many academic papers have focused on modeling [16,17,18,19], control [20,21,22,23,24], and modulation techniques [25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41] for MMCs. The multilevel converter pulse width modulation technique is one of the key technologies for MMCs as it affects the harmonic characteristics, voltage balancing and system efficiency. The space vector modulation (SVM) method can Energies 2017, 10, 581; doi:10.3390/en10040581 www.mdpi.com/journal/energies

Methods

Results

Conclusion