Modified SVM to Reduce CMV and Enhance Output Voltage Quality of Indirect Matrix Converters

  • Alexandros Tsoupos

Student thesis: Master's Thesis

Abstract

High switching-frequency pulse-width modulated (PWM) converters have lead to the development of modern high-efficiency Variable Frequency Drives (VFDs). Their popularity has increased rapidly during the past years due to their capability to control AC motors accurately in order to meet the application requirements and to decrease motor power losses. However, VFDs generate high frequency voltages between the motor neutral point and ground which are called common-mode voltage (CMV). CMV has been proved as one of the main reasons for early bearing failure and winding insulation deterioration. To address this issue, a new space vector modulation (SVM) method for indirect matrix converters (IMCs) is proposed. A novel approach, utilizing the three positive line-to-line input voltages for the rectifier-stage modulation provides the capability of controlling the average DC-link voltage feeding the inverter-stage. This feature is used by the inverter-stage modulation strategy in order to nullify the need of zero-voltage space vectors which are responsible for the generation of high peak common-mode voltage values. Furthermore, the use of only two output voltage space vectors within a sector minimizes the instantaneous error between the reference and generated output voltage, resulting in improved output voltage waveform quality compared to conventional modulation and other proposed modulation strategies that offer common-mode voltage reduction. The switching instants in the inverter-stage are also minimized, resulting in lower switching losses. A trade-off between the aforementioned merits and the input current quality takes place, which, however, can be compensated by proper input filter design. Performance evaluation and comparison between conventional and proposed methods supports the above claims.
Date of AwardMay 2015
Original languageAmerican English
SupervisorVinod Khadkikar (Supervisor)

Keywords

  • Variable Frequency Drives
  • AC Motors
  • Common-Mode Voltage
  • Bearing Failure
  • Winding Insulation Deterioration
  • Space Vector Modulation
  • Indirect Matrix Converters.

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