# Research on Robust Day-Ahead Dispatch Considering Primary Frequency Response of Wind Turbine
## 4 Results
### Wind Power Primary Reserve  
The primary reserve is provided by the conventional synchronous generator and the wind power units. When the wind power is not involved in the frequency response, the synchronous generator will respond to the frequency drop caused by the power imbalance of the system. When the wind power unit displays the external frequency regulation features, it could also shoulder the pressure of the PFR of the conventional synchronous generator. The wind power primary reserve is shown as Figure 7 for Scenario 6:  
Retaining the primary reserve indicates that the wind power units could not run at MPPT and that the wind curtailment is inevitable. The cost of the wind curtailment will in turn have a negative impact on the dispatch strategy aiming to cut the cost. Table 2 shows the economic dispatch cost under different cost coefficient of the wind power primary reserve in the case of a serious unit failure (\(P_{loss}\) = 20.6 MW).  
Figure 6: Classification of real-time operating costs.  
Figure 7: Wind power primary reserve.  
The change of the cost coefficient of the primary reserve has an impact on the dispatch strategy of the system. Overall, the total cost rises with the increase in the cost coefficient of the primary reserve. At the same time, the higher the cost coefficient, the lower the primary reserve capacity of the wind turbine. Table 2 shows that when the wind power reserve cost coefficient is lower than that of other synchronous generators, that is, when the cost coefficient is 0 and 100, the wind power reserve sees a smaller change; and when the cost goes up, the primary reserve capacity drops significantly. In fact, the virtual synchronous generator is available for rapid adjustment, and in situations like a failure and DC blocking, the VSG could respond quickly and retain enough primary reserve to stop the frequency from dropping sharply after the failure, thus gaining more time for other adjustment measures.  
In addition, the pressure of the primary frequency response of the system goes up with the increase of the lost power. At this time, the importance of the frequency regulation of the wind power units is obvious. In this study, we consider the key subset [6;49], and solve it with Equation (30) as the target. When the wind power has no frequency regulation capability, the maximum power lost at the time of the system frequency constraint is 20.4181 MW. However, when the wind power is involved in the primary reserve, the primary frequency response capability strengthens and the power loss stands at 21.3198 MW. It is worth noting that, as the lost power increases and the frequency drops, the selected key subsets may change, and load shedding might occur during the dispatch process.  
In addition, we compare the calculation results of the reserve mode (10% \(P_{N}\)) with the proposed wind power fixed capacity and constraint model. For the adopted fixed-capacity reserve mode, the wind power frequency regulation capability can be fully exploited, and the total reserve of the 24 time periods reaches 336 MW, far exceeding the results from the model proposed in this paper; additionally, the economic cost also reaches $5,659,286. Generally speaking, the high cost for the fixed reserve capacity poses a great demand on the VSG technical parameters and entails a low flexibility. If we are to fully exploit the adjustment capability of renewable energy to accommodate the new energy in the grid, this mode is not an applicable one.