## 6 Simulation Results
### Case Studies
The active power output of the WTG is decoupled from the system frequency and cannot respond to the frequency fluctuations of the power system, which results in the failure to excavate the frequency regulation potential of the WTG. When the strategy proposed in this paper is adopted, the lowest point of the rotor speed of the WTG is 0.711 pu, which fully releases the kinetic energy of the rotor and effectively improves the frequency regulation ability of the WTG. Case 5: The wind speed is 11 m/s, and the load disturbance is 0.5 MW at 5 s. The strategy proposed in this paper is compared and analyzed with the WTG without frequency regulation control and the WTG with comprehensive inertia control. The simulation results are shown in Figure 13.  
As can be seen from the simulation results in Figure 13, when the WTG does not have frequency regulation capability, the lowest point of frequency is 49.325 Hz. When the WTG adopts the comprehensive inertia control and the strategy proposed in this paper, the lowest points of frequency are 49.440 Hz and 49.490 Hz, respectively. At the same time, the strategy proposed in this paper can slow down the frequency drop rate. It can be seen from the response of rotor speed that the lowest point of rotor speed is 0.741 pu when the strategy proposed in this paper is adopted. When comprehensive inertia control is adopted, the rotor speed of the WTG is 0.799 pu, which cannot fully release the kinetic energy of the rotor. When the WTG has no frequency control ability, the rotor speed and active power output do not change, and the kinetic energy of the rotor cannot be effectively utilized. Therefore, the proposed strategy can fully release the frequency regulation ability of WTG and effectively improve the frequency stability of the system. Case 6: The wind speed is 13 m/s, and the system suddenly increases the load by 0.5 MW at 5 s. The strategy proposed in this paper is compared and analyzed with  
Figure 13: Comparison results for Case 5. (**a**) Frequency. (**b**) Rotor speed. (**c**) Output active power of WTG. comprehensive inertia control and without frequency regulation. The simulation results are shown in Figure 9:0  
As can be seen from the simulation results in Figure 14, the strategy proposed in this paper can effectively improve the lowest frequency of the system. When the WTG has no frequency regulation ability, the lowest point of frequency is 49.638 Hz. When the WTG adopts the comprehensive inertia control and the strategy proposed in this paper, the lowest points of frequency are 49.711 Hz and 49.773 Hz, respectively. For the rotor speed response of WTG, the rotor speed is maintained near the rated value under the high wind speed scenario, so the rotor speed does not fluctuate greatly. However, in the case of high wind speeds, the frequency regulation capacity of the WTG is easily affected by the capacity limit of the converter. When the strategy proposed in this paper is adopted, the active power output of a wind turbine is 1.192 pu. The influence of converter capacity limits is considered, and the frequency regulation capability of WTG is fully released. In general, the proposed strategy effectively improves the frequency regulation and control performance of WTG.