A Review of Modulation and Control Techniques for Multilevel Inverters in Traction Applications

Abstract

Traction inverter has been the subject of many studies due to its essential role in the proper performance of the drive system. With the recent trend in increasing the input voltage in battery-powered electric vehicles, multilevel inverters have been proposed in the literature as a promising substitute for conventional twolevel traction inverters. A critical aspect of utilizing multilevel structures is employing proper control and modulation techniques. The control system structure must be capable of handling a number of key issues, like capacitor voltage balancing and equal power loss sharing, which arise in multilevel topologies. This paper presents a review of the present-day traction drive systems in the industry, control and modulation techniques for multilevel structures in the inverters, as well as the principal challenges that need to be addressed in the control stage of the multilevel traction inverter. A comparison has been made between different methods based on the most important criteria and requirements of the traction drive system. Finally, future trends in this application are presented and some suggestions have been made for the next generation of traction drives.

Multilevel Inverter: A Survey on Classical and Advanced Topologies, Control Schemes, Applications to Power System and Future Prospects

“…This configuration possesses the primary merit of generating more output voltage levels using very few numbers of switches in contrast to other conventional MLI topologies. Therefore, SSPS-MLI can be applied in the areas of: (i) electric vehicle where a single unit of the battery can be composed of several series-connected battery cells [171]; (ii) vehicle drive system to meet voltage or power need by a possible combination of two or more sources either in series or in parallel and (iii) traction purposes by possible joining of multiple sources in various flexible configuration [168,172]. (ii) Symmetric H-bridge Topology This family of MLI usually consists of inverters where the magnitude of all the isolated supply DC sources to each of the H-bridge cells is identical.…”

Impact Evaluation of Innovative Selective Harmonic Mitigation Algorithm for Cascaded H-Bridge Inverter on IPMSM Drive Application

“…Multicarrier PWM modulation schemes for multilevel converters represent an extension of the strategies for the twolevel converter. Indeed, in literature are available several PWM modulation strategies based on the different dispositions of the triangular carrier signals like Level Shifted (LS) and Phase Shifted (PS), as discussed in [20] and [47]. In respect to the LS, the main feature of the PS is that the line-voltage harmonics are centered at a frequency fh, defined as:…”

“…However, the performances of the electric drive, are not only a function of the aforementioned control techniques but also of the modulation technique employed especially when a multilevel inverter is adopted [19]. The main control techniques and modulation strategies for multilevel inverters in traction applications have been discussed in [20]. More in detail, through a set of selection criteria based on traction systems requirements the control and modulation schemes, have been compared.…”

“…Similar studies are reported in [38]- [39], where the performance of seven-level and nine-level CHBMI converters are presented, respectively. Although numerous studies about multilevel structures in different traction applications proposed them as a promising substitute, the worldwide markets have not used these topologies yet [20].…”

Implementation of a Novel Variable Structure Nearest Level Modulation on Cascaded H-Bridge Multilevel Inverter

“…Some more topologies which utilize SHE modulation technique are discussed in [18]- [21]. A comprehensive review of different modulation techniques for traction purposes is presented in [22]. When the number of levels are low, NLC can easily applied in comparison to SHE.…”