With the continuous expansion of the scale and capacity of offshore wind power, the adoption of high-voltage direct current transmission technology has become an inevitable choice for achieving efficient long-distance transmission, in which the use of medium-frequency AC collection with diode rectifier unit (DRU) to achieve high-voltage direct current transmission is considered one of the optimal schemes. However, the nonlinearity of DRU will cause wind power grid-connected converters to generate heavy harmonic currents, which will have adverse effects on the offshore power grid and threaten its safe and stable operation. To solve this problem, a harmonic suppression strategy is proposed for the medium-frequency AC collection and uncontrolled rectification system of offshore wind power. Under this strategy, the grid-connected harmonic current is calculated using the instantaneous power theory in a two-phase stationary coordinate system, and the voltage waveform on the grid side of the wind turbine is actively adjusted by combining with model predictive control (MPC). This can effectively reduce the harmonic current generated by the DRU and ensure the safe and stable operation of the offshore power grid. Simulation and experimental results validate the effectiveness and feasibility of the proposed suppression strategy.
| 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 |