Modeling and Control Strategy for Capacitor Minimization of Modular Multilevel Converters

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dc.contributor.authorLyu, Yadongen
dc.contributor.committeechairLee, Fred C.en
dc.contributor.committeechairLi, Qiangen
dc.contributor.committeememberHa, Dong S.en
dc.contributor.departmentElectrical and Computer Engineeringen
dc.date.accessioned2017-02-21T09:00:42Zen
dc.date.available2017-02-21T09:00:42Zen
dc.date.issued2017-02-20en
dc.description.abstractThe modular multi-level converter (MMC) is the most prominent interface converter used between the HVDC grid and the HVAC grid. One of the important design challenges in MMC is to reduce the capacitor size. In the current practice, a rather large capacitor bank is required to store line-frequency related circulating energy, even though a number of control strategies have been introduced to reduce the capacitor voltage ripples. In the present paper, a novel control strategy is proposed by means of harmonic injections in conjunction with gain control to completely eliminate both the line frequency and the second-order harmonic of the capacitor voltage ripple. Ideally, the proposed method works with the full bridge topology. However, the concept also works with half bridge topology with a significant reduction of line frequency related ripple. To gain a better understanding of the nature of circulating energy and the means of reducing it, the method of state plane analysis is employed to offer visual support. In addition, the design trade-off between full bridge MMC and half bridge MMC is presented and a novel control strategy for a hybrid MMC is proposed. Finally, the work is supported with a scaled down hardware demonstration.en
dc.description.abstractgeneralThe modular multi-level converter (MMC) is the most prominent interface converter used between the HVDC grid and the HVAC grid. One of the important design challenges in MMC is to reduce the capacitor size. In the current practice, a rather large capacitor bank is required by the commonly used control strategy. The large capacitor bank increases the cost and the space of the MMC system. In the present paper, a novel control strategy is proposed to significantly reduce the capacitor bank in the system. Ideally, the proposed method works with the full bridge topology. However, the concept also works with half bridge topology with a significant reduction of capacitor bank. To gain a better understanding of the nature of the operating principles of capacitors, the method of state plane analysis is employed to offer visual support. In addition, the design trade-off between full bridge MMC and half bridge MMC is presented and a novel control strategy for a hybrid MMC is proposed. Finally, the work is supported with a scaled down hardware demonstration.en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:9843en
dc.identifier.urihttp://hdl.handle.net/10919/75111en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectModular Multilevel Convertersen
dc.subjectModeling and Controlen
dc.subjectState Trajectoryen
dc.subjectCapacitor Reductionen
dc.subjectFault Protectionen
dc.subjectHybrid MMCen
dc.titleModeling and Control Strategy for Capacitor Minimization of Modular Multilevel Convertersen
dc.typeThesisen
thesis.degree.disciplineElectrical Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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