μ-Synthesis robust coordinated control of variable speed wind power generators and electric vehicles to regulate frequency

Variable speed wind power generators (VSWPGs) can inevitably introduce power fluctuations and reduce the system inertia in modern power systems. On the other hand, VSWPGs also have certain frequency support ability due to the fast control characteristics of the power electronics in the converters. Therefore, it is urgently required for VSWPGs to regulate the frequency of the power system. Taking into consideration the internal and external uncertainty in the power systems and that frequent regulation actions of VSWPGs might lead to mechanical failures and aggravate the aging process of the wind power generators, a coordinated control method of VSWPGs and electric vehicles (EVs) for frequency regulation on the basis of μ-synthesis control is proposed in this paper. The EVs are modeled as energy aggregators, the VSWPGs are modeled under the derating control using the small-signal analysis method, and the dynamic frequency response model for the system with uncertainty is then built. Considering the power system parametric uncertainty, a μ-synthesis controller is implemented to tackle the coordinated control problem of VSWPGs and EVs regulating system frequency by means of the D-K iterative method. Then the comparisons through time-domain simulations are conducted to verify the presented coordinated strategy is able to overcome influence of uncertainty on system frequency and also has better dynamic frequency performance.