Full
Outline
Aimed at an offshore wind power flexible DC transmission project, the problems of the large mass and volume of modular multilevel converters (MMCs) and the high construction cost of offshore converter stations need to be solved urgently. Therefore, the lightweight research of MMC is one of the research hotspots at present. First, an optimized configuration MMC (OC-MMC) is proposed, and its configuration method is given. In addition, a voltage balancing strategy is designed based on the nearest level modulation. The novel converter improves the number of output voltage levels on the AC side by introducing two submodules whose capacitance values are the same but the rated voltage values are proportional by a factor of K. Then, through the simulation results on a MATLAB/Simulink platform and experimental results, it is found that the novel converter can successfully complete the voltage conversion process. The steady-state operation characteristics of the system are similar to those of a conventional MMC, and the dynamic characteristics are good. On the premise that the numbers of AC voltage levels of the two converters are the same, the proposed OC-MMC can indirectly reduce the number of submodule assembly and reduce the mass, volume and construction cost of the converter stations compared with the conventional MMC, so as to achieve the goal of lightweight.
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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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