DC-Link Voltage Balancing Modulation for Cascaded H-Bridge Converters

Youngjong Ko,Anatolii Tcai,Marco Liserre

doi:10.1109/access.2021.3098896

Abstract

Cascaded H-Bridge (CHB) converters have been widely employed in various applications, providing the advantages of modularity and multilevel voltage output. However, technically the CHB converters require isolated DC-link buses, which need to be regulated individually. In this context, a control scheme for the CHB converters features the voltage balancing algorithm. The voltage balancing control is typically performed by PI controller, where its control capability is limited by linear modulation region. In this work, the modulation based voltage balancing algorithm is proposed, which extends the balancing control capability and improves the dynamic performance. The proposed method is theoretically analyzed and validated through the simulation and experimental results.

Highlights

Cascaded H-Bridge (CHB) converters feature modularity, multilevel voltage output, and low dv/dt, which offers merits to high power applications [1]–[3]
The power imbalance among the cells shall be further elevated. As another example, considering that individual cell has different Remaining Useful Lifetime (RUL), the power routing strategy was proposed in [8], [9], which aims at unequally redistributing total power among the cells
EXPERIMENTAL RESULTS The proposed method is experimentally validated in the developed prototype and its configuration is shown in Fig. 12, where the CHB converter consists of three cells

Summary

INTRODUCTION

Cascaded H-Bridge (CHB) converters feature modularity, multilevel voltage output, and low dv/dt, which offers merits to high power applications [1]–[3]. In [15], level-shifted carriers based method was developed in order to extend the voltage balancing capability This method cleverly utilizes the inherent feature of uneven loading power of each cell. In the control-based approach, the reactive power compensation method was presented in [16], its voltage balancing capability is still limited by the linear modulation range. A novel modulation strategy is proposed, which utilizes two operation modes: clamped mode and nonclamped mode, to perform the voltage balancing control. For a higher loading power, the amplitude is increased, whereas it decreases for a lower loading power In this context, it can be noticed that the control capability is limited by the linear modulation range of additional loading cells. This is an attractive feature, which enables a faster dynamic response

II III IV vc vnc vnc tbal tbal vc

SIMULATION VALIDATION

EXPERIMENTAL RESULTS

CONCLUSION