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CONTROL OF MULTILEVEL CONVERTERS FOR VOLTAGE BALANCING AND FAULT-TOLERANT OPERATIONS

Saha, Aparna, Saha
http://rave.ohiolink.edu/etdc/view?acc_num=akron1512661551448008

Abstract Details

2017, Doctor of Philosophy, University of Akron, Electrical Engineering.
Multilevel converters (MLC) have been widely accepted in recent times for high power and medium to high voltage applications. Developments in semiconductor technology and commercial availability of high power switches have made two-level voltage-source converters (VSC) feasible for high power applications; however, for high voltage and high power systems, instead of using switches with high voltage ratings, it is beneficial to connect multiple low-voltage rated switches in series in multilevel approach. Compared to conventional two-level VSCs, MLCs have better capability to (i) lower harmonic distortion of the AC-side waveforms, (ii) decrease the dv/dt switching stresses, and (iii) reduce the switching losses. Moreover, MLCs are easily configurable with multiple renewable energy sources such as solar power, wind power, and fuel cells. Among diverse MLC topologies, diode-clamped converter (DCC) configuration is analyzed in this dissertation. The salient feature of DCC topology is that all three phases of the converter share a common DC bus voltage which minimizes total capacitor requirements. However, DCCs have their own limitations such as the voltage balancing among the converter cells and control complexity. Due to the series connection of the dc-capacitor cells, the voltage sharing among the cells deteriorates during certain operating conditions. To have increased number of voltage levels at the output, DCCs require a higher number of power semiconductor switches and associated electronic components. That means multilevel DCCs are more difficult to control and more expensive than two-level VSCs. There is also a much higher possibility of a device failing. To improve the reliability and performance stability of the overall converter system, an easily configurable controller with a fault-tolerant capability is essential. This dissertation presents the development of generalized control algorithms and a novel converter topology to address the inherent technical issues associated with the higher-level DCC system. A unique space-vector pulse width modulation (SVPWM) based controller is developed for 3-level and 5-level DCC with minimal switching operation that ensures voltage balancing and minimizes switching loss. The effectiveness of the proposed SVPWM controller is further validated through multilevel DCC operations at high modulation index without any additional balancing circuitry. The fault-tolerant capabilities of multilevel DCC are also improved by using a new SVPWM controller, which ensures continuous operation under certain device failures. Moreover, a novel three-phase multilevel DCC topology is proposed that reduces the power electronic device counts remarkably with the increase of output voltage levels while maintaining control flexibility. The developed control algorithms are implemented in the DCC topology and their operations are experimentally verified.
Yilmaz Sozer (Advisor)
Malik Elbuluk (Committee Member)
Seungdeog Choi (Committee Member)
Ping Yi (Committee Member)
Kevin Kreider (Committee Member)
138 p.
Electrical Engineering
Multilevel Converter, Space Vector Pulse Width Modulation, SVPWM, Diode-Clamped Converter, Voltage Balancing, Fault-tolerant, New multilevel topology, Minimum loss SVPWM

Recommended Citations

Citations

  • Saha, Saha, A. (2017). CONTROL OF MULTILEVEL CONVERTERS FOR VOLTAGE BALANCING AND FAULT-TOLERANT OPERATIONS [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1512661551448008

    APA Style (7th edition)

  • Saha, Saha, Aparna. CONTROL OF MULTILEVEL CONVERTERS FOR VOLTAGE BALANCING AND FAULT-TOLERANT OPERATIONS. 2017. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1512661551448008.

    MLA Style (8th edition)

  • Saha, Saha, Aparna. "CONTROL OF MULTILEVEL CONVERTERS FOR VOLTAGE BALANCING AND FAULT-TOLERANT OPERATIONS." Doctoral dissertation, University of Akron, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1512661551448008

    Chicago Manual of Style (17th edition)

akron1512661551448008
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© 2017, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.