Cooperative Control of Wind Power Generator and Electric Vehicles for Microgrid Primary Frequency Regulation

TLDR

Wind generators and plug‑in hybrid electric vehicles are rapidly increasing in modern power grids, yet each faces practical constraints that limit their individual ability to provide primary frequency regulation in low‑inertia microgrids; however, when combined with coordinated control, they can compensate for each other’s drawbacks, yet no cooperative control strategy has been proposed. This study uses small‑signal analysis to determine whether droop or virtual inertia control is more suitable for cooperative frequency regulation between wind generators and PHEVs. The authors examine centralized and distributed coordination structures to ensure that source constraints and communication delays are respected while enabling cooperation. Analytical and time‑domain simulation results show the advantages, disadvantages, and suitable applications of centralized versus distributed structures, confirming the analytical predictions.

Abstract

Wind generators and plug-in hybrid electric vehicles (PHEVs) are increasing rapidly in modern power grids. Despite all their merits, these two classes of sources are limited by some practical constraints which disqualify each of them from effectively contributing separately to the primary frequency regulation in power grids with reduced inertia, such as microgrids. However, when combined with proper control and coordination, wind generators and PHEVs can compensate for the individual drawbacks of each source and effectively participate in the frequency regulation. A cooperative control strategy that considers the practical limits of both sources is not available in the literature. To fill this gap, in this paper, small-signal analysis is employed to investigate which frequency regulation method, droop or virtual inertia, is more suitable for such cooperation. The centralized and distributed control structures are examined as two possible coordination methods to ensure that the wind generator and PHEVs constraints are not violated and also that the communication system delay is considered. Based on a detailed analysis, the advantages, disadvantages, and appropriate applications of the centralized and distributed structures are discussed. Time-domain simulation results, obtained by using a typical microgrid system, validate the analytical results.