Frequency Characteristics Analysis of Isolated Power Grid Based on VSC Droop Controller

Abstract

With the rapid development of renewable energy like wind power and photovoltaics, the penetration of renewable energy in the future power system will increase continually, and the system frequency characteristics will change significantly. At present, isolated power grid is an effective way for utilizing and consuming the renewable energy. Nevertheless, due to the high penetration of renewable energy in isolated power grid, the inertia of the system is insufficient. When the active power disturbances occur, system frequency will fluctuate greatly, which will seriously affect the safe and stable operation of isolated power grid. Therefore, it is of great significance to clarify the frequency dynamic characteristics of isolated power grid. The topology of an actual isolated power grid is given first in this paper, and a frequency response characteristics model which is suitable for frequency characteristics analysis is raised. Then a synchronous generator penetration coefficient is defined, and the frequency response characteristics of the isolated power grid are analyzed in two different cases as renewable energy does not participate in frequency regulation and participates in frequency regulation through droop controller. Subsequently, a relationship curve of power disturbance, frequency deviation and synchronous generator penetration coefficient is shown in this paper. Finally, the proposed frequency characteristics analysis method is verified based on PSCAD/EMTDC simulation test platform.