Negative-Sequence Current Injection Based Islanding Detection and Seamless Transfer for Microgrids
碩士 === 國立清華大學 === 電機工程學系 === 100 === This thesis presents the seamless transfer between grid-connected and islanded modes for a single voltage-sourced converter (VSC) based microgrid system. Principles of the control strategies at both modes are introduced where current-mode control for grid-connect...
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| Format: | Others |
| Language: | en_US |
| Published: |
2012
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| Online Access: | http://ndltd.ncl.edu.tw/handle/51726982250470184442 |
| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 100 === This thesis presents the seamless transfer between grid-connected and islanded modes for a single voltage-sourced converter (VSC) based microgrid system. Principles of the control strategies at both modes are introduced where current-mode control for grid-connected operations and autonomous-mode control for islanded operations. The smooth transition from grid-connected mode to islanded mode is based on an islanding detection method that actively injects a negative-sequence current (4% of the rated value) as a disturbance signal via a negative-sequence controller which is adopted as the complementary of the conventional VSC controller. The estimated magnitude of the corresponding negative-sequence voltage at the point of common coupling (PCC) is used as the islanding detection signal. A quantitative analysis based on symmetrical component transformations is proposed to support the feasibility of the islanding detection scheme. For the islanded mode to grid-connected mode transition, a phase compensation scheme that increases or decreases the operating frequency of the VSC is applied for grid resynchronization. The detailed process of the seamless transfer between these two modes is illustrated. Finally, simulations in PSCAD software environment and hardware experiments verify the theoretical analysis.
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