With the increasing proportion of wind turbines connected to grid, the security and stability problem caused by wind farm separated from power grid are becoming more and more serious. So it is particularly important to improve DFIG fault ride through capacity and reduce the occurrence of offgrid events. In view of the problems, existing DFIG fault ride through control schemes are introduces first. Considering that frequently switched of DC chopper circuit is easy to cause voltage waveform distortion and supercapacitor control scheme has high economic cost, the DFIG fault ride through control scheme based on smart chopper circuit is further proposed. The proposed method is upgraded based on DC chopper circuit. It connects the unloading resistance with the DC bus through DC/DC converter and introduces active powerDC voltage droop control link to adjust the circuit resistance power dynamically during fault period. Besides it sets two modes of high and low voltage crossing, which can be started automatically according to grid connected voltage. Finally, the smart chopper circuit control scheme is verified in Matlab/Simulink. The simulation results show that considering the DC bus voltage suppression effect, the regulation time for voltage recovery, the distortion degree of rotor current and the economic cost of schemes, fault ridethrough control of DFIG based on smart chopper circuit has the most advantages.
| 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 |