Incorporating DFIG-Based Wind Power Generator in Microgird Frequency Stabilization

Abstract

Although wind power as a renewable energy is assumed to be an all-round advantageous source of energy, its intermittent nature can cause difficulties, especially in the islanding mode of operation. Conventional synchronous generators can help to compensate for wind fluctuations, but the slow behavior of such systems may result in stability concerns. In this study, the virtual inertia method, which imitates the kinetic inertia of a synchronous generator, is used to improve the system’s dynamic behavior. Since the proposed method incorporates no long-term power regulation, it requires no mass storage device and is thus economical. To preclude additional costs, a rotating mass connected to the Doubly Fed Induction Generator (DFIG) shaft or a super-capacitor connected to the DC-link on a back-to-back converter of a wind power generator could be used. The concept and the proposed control methods are discussed in detail, and eigen-value analysis is used to study how the proposed method improves system stability. As well, the advantages and disadvantages of using DFIG rotating mass or a super-capacitor as the virtual inertia source are compared. The proposed approach also shows that while virtual inertia is not incorporated directly in long-term frequency and power regulation, it may indirectly enhance the system’s steady-state behavior. A time domain simulation is used to verify the results of the analytical studies.