# Performance Validation of Control Algorithm Considering Independent Generator Torque Control in PCS
## 5 Conclusions  
A power control algorithm that takes into account the unique characteristics of a medium-sized wind turbine having a sensorless generator speed estimation method and independent generator torque control in the PCS was designed and validated in the study. The performance verification was conducted through simulations using an aeroelastic analysis program (Bladed) for a 100 kW wind turbine and wind tunnel tests using a scaled wind turbine model. According to the simulation results for the 100 kW wind turbine, the PCS torque control showed a tendency to reduce the standard deviation of the rotor speed by up to 24.55% and the standard deviation of the generator output by 13.99% compared to the reference power control under the same conditions. However, it was found that, in the Region III operating zone, the generator torque, which varies with the generator speed, can slightly increase the oscillations in the generator power, highlighting a limitation. Additionally, to improve the existing control transition logic, a control transition algorithm incorporating the PCS torque control was applied. The results showed that the DEL and the maximum value of the tower fore-aft bending moment decreased under the same conditions. Specifically, the DEL decreased by approximately 6.11%, and the maximum value decreased by around 11.75%. Additionally, to experimentally validate the control algorithm, a control algorithm with the same structure was designed for the scaled wind turbine model, and wind tunnel tests were conducted. According to the wind tunnel test results, the PCS torque control reduced the standard deviation of the rotor speed by approximately 3.60%, while the standard deviation of the generator power increased by around 6.15% compared to the reference power control. After applying the control transition logic algorithm to improve this limitation, the standard deviation of the rotor speed decreased by about 21.55%, and the standard deviation of the generator power decreased by approximately 10.77%. This trend was found to be similar to the simulation results. As a future work, the proposed control algorithm will be applied to the 100 kW wind turbine for experimental validation. Additionally, further development of control algorithms aiming at minimizing power fluctuations and improving the control performance of the target medium-sized wind turbine will be performed. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Condition**} & \multicolumn{4}{c}{**Electrical Power (W, \%)**} \\ \cline{2-5}  & **Mean** & **Relative Diff.** & **Std.** & **Relative Diff.** \\ \hline Ref. with Mode SW & 38.84 & - & 1.95 & - \\ PCS with Mode SW & 38.43 & \(-\)1.06 & 2.07 & 6.15 \\ PCS with SPS & 38.23 & \(-\)1.57 & 1.74 & \(-\)10.77 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Comparison of the generator power based on the wind tunnel test results. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Condition**} & \multicolumn{4}{c}{**Rotor Speed (rpm, \%)**} \\ \cline{2-5}  & **Mean** & **Relative Diff.** & **Std.** & **Relative Diff.** \\ \hline Ref. with Mode SW & 676.03 & - & 18.05 & - \\ PCS with Mode SW & 673.36 & \(-\)0.39 & 17.40 & \(-\)3.60 \\ PCS with SPS & 670.87 & \(-\)0.76 & 14.16 & \(-\)21.55 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Comparison of the rotor speed based on the wind tunnel test results. The proposed control algorithm was specially designed for a medium-size wind turbine having unique characteristics of sensorless generator speed estimation and independent generator torque control in the PCS. Therefore, it is not applicable to conventional large-scaled wind turbines having both generator torque control and blade pitch control in the PLC. Conceptualization, D.K. ; Methodology, D.K. ; Software, D.K. and M.-W.H. ; Supervision, I.P. ; Validation, D.K. and M.-W.H. ; investigation, D.K., W.R. and A.A.; data curation, D.K. ; Writing--original draft, D.K. ; Writing--review and editing, I.P.