Full
Outline
HVDC transmission systems based on modular multilevel converters (MMCs) face many problems, e.g., the DC fault current cannot be cleared by a half-bridge submodule topology, and the submodule capacitor voltage sequencing requires too much computation and high real-time performance of sensors. Aimed at these problems, a modified full-bridge MMC with fault current self-clearing and module capacitor voltage self-balancing capabilities is proposed in this paper. By accessing a branch consisting of two IGBTs in reverse series on the same side of the adjacent full-bridge submodule, a path is provided for directly connecting the capacitors of adjacent submodules in parallel. In addition, its operating modes in different states are analyzed, and the corresponding dynamic distribution voltage balancing control strategy is designed. By adding the parallel operation state of capacitors, the modified full-bridge MMC can realize voltage self-balancing between the capacitors of different submodules on the same bridge arm without monitoring the submodule capacitor voltage, thus effectively reducing the complexity and calculation amount of the controller. Meanwhile, the parallel input of capacitors can also reduce the output from individual capacitors, thereby reducing the capacitor voltage fluctuations. Finally, the simulation results in RT-LAB show that the DC fault current self-clearing and submodule capacitor voltage self-balancing can be realized simultaneously by using the proposed voltage balancing control strategy.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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