Investigation and Suppression of Harmonics and Interharmonics in High-Power PWM Current-Source Drive Systems

• Author / Creator

  Zhang, Ye

• Among the medium-voltage (MV) high-power industrial drive applications, the PWM current-source drive systems are increasingly used in recent years, due to the simple structure, motor friendly waveforms and fuseless short-circuit protection. A typical challenge being faced by the high-power PWM current-source drives is the problem of harmonics and interharmonics. The harmonics and interharmonics from utility, load, power converters and harmonics interaction between rectifier and inverter may cause a host of impacts on the drive system, such as the deterioration of line power quality, load torsional vibration, LC resonance occurrence, etc.
  To solve this problem, this thesis conducts an in-depth study on the harmonics and interharmonics in high-power PWM current-source drive systems, including the mechanism of generation, the impacts on the system, and the active attenuation through the high-power converters. On the one hand, with respect to the generation of harmonics and interharmonics, a systematically investigation of the harmonics interaction phenomenon in high-power PWM current-source drives with thyristor front end (TFE) and active front end (AFE) is carried out respectively. The harmonics interaction is a main source of interharmonics in high-power current-source drive systems and has not been well considered in previous works. For the high-power PWM current-source drives with AFE, where the harmonics interaction phenomenon is more complex due to the PWM converters and LC circuit contained in each ac side, a frequency iteration method is proposed to analyze the produced interharmonics with possible frequencies. In addition, the impacts of the harmonics and interharmonics on the drive systems are carefully studied with respect to three main cases, line-side communication interference, load torsional vibration, and LC resonance excitation. The mechanism and cause factors of impacts’ occurrence are analyzed in details, and the frequencies of the harmonics and interharmonics that results in the impacts at certain motor operating frequencies are accurately estimated under each case. On the other hand, to attenuate the harmonics and interharmonics without involving additional costs and losses, at first, the active interharmonic compensation capability of high-power PWM current-source converters, which are commonly modulated by the selective harmonic elimination (SHE) scheme, is enabled by a proposed SHE phase jittering method. Such active compensation method can be easily designed and implemented. Based on a dc-link virtual impedance concept, it is applied to actively attenuate the interharmonics caused by the harmonics interaction in high-power PWM current-source drives in this thesis. Besides, the proposed SHE phase jittering method is also developed to actively compensate the system background harmonics from the utility and the load. Compared with the active harmonic compensation strategies of SHE-modulated high-power PWM converters in previous works, the SHE-phase-jittering-based active compensation not only saves the effort on off-line calculations, but also realizes the on-line real-time harmonic compensation without any delay introduced.

• Subjects / Keywords

  • Current-source drives
  • Harmonics
  • High-power drives
  • Interharmonics

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3CN6Z47V

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.