## 5 Results and Analysis
This is the reason why the simulation curves are similar but not identical. Results are presented in Figure 13, where it is observed that both mechanisms fulfil the mission correctly with a similar performance. Finally, power reference switching will be used in the future because its implementation is simpler. The last experiment maintains all conditions as before but includes the gain scheduling adaption. However, the interdependence between the CPC and PTC parameters is strong in a nonlinear relationship. Moreover, the parameters of the CPC are also gain-scheduled. For this reason, it is difficult to establish for each gain of the PTC a clear functional dependence between power reference values. Therefore, the present solution is a lookup table implementation. Figure 12: Power tracking control in Region III for \(P_{ref}>P_{max}\) without gain scheduling. To this end, ten values of the power reference are selected in 2.5 MW steps, and the controller parameters are obtained for each one. The gains are organised in a lookup table whose input is the power reference, and the transitions are smoothed by linear interpolation. The values are given in Table 3.  
The large values in Table 3 might be striking. This is due to the fact that the simulation programme is designed in the MKS system, i.e., the power is given internally in watts. Since the reference is expressed in megawatts, the variables are multiplied by \(10^{6}\). This last simulation experiment considers together all characteristics of the new approach. Therefore, not only the power but also the generator speed are included in the analysis. The results are shown in Figure 14, where one observes that the parameter adaption improves the controller performance at every value of the power reference as well as the generator speed. The generator speed is correctly adjusted following the reference provided by the power controller. The results of the previous experiment (solid grey lines) are also included here for comparison purposes. It is important to mention that it seems that the pitch angle suffers unrealistic step jumps. However, this is an incorrect appreciation. The pitch actuators have a maximum  
Figure 13: Power tracking control with compensation for power output saturation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Power** & \(\mathbf{K_{p1}}\) & \(\mathbf{K_{p2}}\) & \(\mathbf{K_{p3}}\) & \(\mathbf{K_{p4}}\) \\ \hline
2.5 MW & 4,917,724.78 & \(-\)961,828.98 & 28,624.90 & \(-\)30,439.48 \\
5.0 MW & 4,303,206.38 & \(-\)1,091,072.92 & 29,850.07 & \(-\)32,261.70 \\
7.5 MW & 4,204,105.14 & \(-\)1,112,899.75 & 29,149.42 & \(-\)37,485.53 \\
10.0 MW & 4,159,777.78 & \(-\)1,124,248.68 & 28,372.58 & \(-\)39,348.81 \\
12.5 MW & 4,637,930.70 & \(-\)1,140,480.25 & 23,531.99 & \(-\)45,349.06 \\
15.0 MW & 5,003,476.51 & \(-\)1,010,485.75 & 14,857.08 & \(-\)49,130.02 \\
17.5 MW & 5,716,598.38 & 1,029,539.49 & 8457.86 & \(-\)57,567.16 \\
20.0 MW & 7,551,108.51 & \(-\)5,121,574.18 & 1825.18 & 786.39 \\
22.5 MW & 1,747,656.93 & \(-\)17,611.36 & 4079.56 & \(-\)5664.53 \\
25.0 MW & 1,650,520.30 & \(-\)131,675.54 & 16,452.65 & \(-\)18,028.40 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Controller parameters for the gain scheduling of the power tracking controllers. speed of \(\pm 8\) deg/s. Hence, a maximum step of 11 degrees is covered in 1.4 s, an amount that cannot be observed on the minute-scaled axis.