## 5 Conclusions  
An improved structure of a minimum-variance controller is proposed in this paper, by designing a self-tuning mechanism of the control penalty factor (as a contribution), in order to extend the allowed value range of disturbances, and therefore, implicitly to extend the operating range of the control system. The value of this parameter (\(\rho\)) decisively influences the minimum variance control system performance. As a novelty, unlike the classic minimum-variance control, which involves a constant value of \(\rho\), the proposed solution supposes a real-time tuning of this controller parameter, based on system output error measurement. The tuning mechanism implements a bipositional switching strategy that considers a sharp hysteresis loop to adjust \(\rho\). Therefore, when the system output error exceeds a certain threshold, \(\rho\) is set to a higher value, improving the system robustness against disturbances. However, because the best control performances are obtained for a small value of \(\rho\), this high-level penalty of control is maintained only at the beginning of the transient regime that occurs due to external disturbances. When the output error drops below a certain threshold, the proposed mechanism resets the control penalty factor to the previous small value (constant in the steady state regime), which ensures the best control system performance. Such a tuning strategy is an efficient solution to stabilize a highly disturbed system, while ensuring good control performance. The performed studies proved that a constant value of \(\rho\) (small or high) allows a limited operating range, the control system being destabilized by disturbances that exceed certain levels. By using this strategy (involving a variable control penalty factor), the process operating range can be extended and the control system can withstand higher disturbances in stable operating conditions.  
The proposed strategy was validated for the case of an induction generator integrated into a wind energy conversion system and disturbed by two major external perturbations: mechanical torque variations and terminal electrical load/unload. Operating under the action of strong disturbances (wind gusts, electrical load variations), the extension of safe operating range (thus avoiding the system disengagement) is an important goal of such an energy conversion system. The results of the performed tests are relevant, proving the possibility of a stable system operating regime, even under the action of higher disturbances with over 50% above the limit values allowed if \(\rho\) would be constant. Although the tuning strategy was validated for the particular case of an induction generator, the control solution could be used for other highly disturbed processes, especially when the perturbations are difficult (or even impossible) to measure.  
[PERSON] and [PERSON] performed the design of the proposed control strategy. [PERSON] and [PERSON] performed the simulation and analyzed the obtained results. [PERSON] and [PERSON] elaborated the case studies. All authors have structured and approved the final manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.