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Post-Fault Control of Fault-Tolerant Multi Module Converters

Kazemi, Hossein | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 49661 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Zolghadri, Mohammad Reza
  7. Abstract:
  8. Nowadays, multilevel converters are significantly developed in industrial applications as well as energy transmission systems regarding proper quality of output waveforms and fault tolerant operation ability. Among the different topologies of multilevel converters, modular multilevel converter (MMC) due to its modularity feature it more accepted in high voltage direct current (HVDC) transmission systems. Fast fault detection in power electronics converters is necessary to bypass the defected part in order to prevent failure propagation to other Submodules and to provide continues servicing. On this basis, different researches are reported in literature for MMCs fault tolerant operation. In this thesis, two new post fault control strategies using active and semi active Submodules are proposed in order to decrease the complexity and voltage stress on semiconductor devices and transient time. In first method, the reserve Submodules are considered as active Submodules. After that, some Submodules are selected to generate output voltage and the remains Submodules are bypassed as circular reserve ones. Therefore, the MMC faulty condition is directed to normal operation by isolating the faulty submodule and replacing it with a reserved submodule. In second method, the reserve submodules have the hybrid structure including a combination of two usual MMC submodules acting as one submodule. In faulty condition, after decomposing the hybrid to two submodules, the number of levels remains unchangeable. However, capacitor of the decomposed submodule charges from half of the nominal value to the nominal value. Simulation results are presented in order to verify the performance of proposed MMC fault tolerant operation strategies
  9. Keywords:
  10. Cascaded Converter ; Fault-tolerant Control ; Error Resilient ; High Voltage DC Power Transmission ; Modular Multilevel Converters (MMC) ; Redundant Submodules ; Hybrid Cells

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