Full
Outline
The problem of neutral-line voltage harmonics in Zhangbei flexible HVDC transmission system results in the following effects. The capacitor in a neutral-line voltage transformer will generate harmonic current due to the influence of high-order harmonics in the system, which makes the capacitor device heat up seriously and fail to work accordingly. The switching of capacitors may cause harmonic amplification in the system, which may also affect the stable operation of other electrical equipment nearby and thus pose a major threat to the safety and normal operation of the power system. To solve this problem, first, a harmonic analysis model of an modular multilevel converter (MMC) is established, and the harmonic interaction between AC and DC in a multi-terminal flexible HVDC transmission system is analyzed in detail. Then, the research results of harmonic characteristics of a converter station are further applied to Zhangbei flexible HVDC transmission system, the characteristic harmonics of the neutral-line voltage of the system are obtained. Finally, a model of Zhangbei flexible HVDC transmission system is also built, and a control strategy of DC active damping is adopted to suppress resonance using the PSCAD simulation software, and it is verified that this strategy can effectively suppress harmonics of the neutral-line voltage.
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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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