Frequency Response Improvement through Coordinated Control of Virtual Power Plants

With the increasing proportion of Distributed Energy Sources (DERs), it is difficult to meet the frequency regulation requirement of the power system by relying only on traditional thermal power due to the reduction of the overall available rotational inertia in the system. Virtual Power Plant (VPP) aggregates DERs to operate as a single generating unit, thus providing the services of regulating reserve and frequency support, and reducing the frequency regulation pressure of traditional thermal power units to a certain extent. In this vein, to address the problem of declining frequency stability in low-inertia power systems, this paper proposes a coordinated frequency control method for VPP. First, a centralized VPP control strategy is adopted to ensure the consistent response of DERs, and the frequency regulation characteristics of each type of DERs are analyzed and the corresponding control strategy is designed. Second, by measuring the interaction signals between the VPP and the transmission grid, the coordinated feedback signals are distributed to the local frequency controllers of the DERs to "amplify" the sensitivity of the local frequency controllers to the frequency deviation in order to improve the control effect. Finally, the proposed control method is evaluated based on the modified WSCC-9 system. The results show that the proposed method can minimize the system frequency deviation and frequency variation, shorten the time required for frequency regulation, and improve the frequency regulation effect.