Inertia and Damping Analysis of Grid-side DC/AC Inverter Control Strategy for Direct-drive Wind Turbine

Abstract

With the large-scale connection of direct-drive wind turbine (WT) to the power grid, the proportion of installed capacity and rotational inertia of traditional power grids have been reduced, and the dynamic support capacity of the power grid has been relatively weakened, which increase the difficulty of system inertia effect control and steady-state mechanism analysis. In this paper, a DC voltage droop control strategy under high-frequency components is proposed. This control method can play a positive role in reducing the grid frequency deviation and to promoting the analysis of the rate of change of frequency. Firstly, a static synchronous generator (SSG) mathematical model of a wind power system is established by analogy to the dynamic analysis theory and method under the traditional electromechanical time scale. Secondly, from the perspective of DC-voltage timescale (DVT) dynamic characteristics analysis and control, the inertia, damping and synchronization effects of the WT are studied, and the mathematical expressions of the system equivalent parameters are derived. Finally, through the comparison between conventional droop control and high-frequency component droop control, the advantages and disadvantages can be obtained, subsequently, the effectiveness of the high-frequency droop control on the DC side and the correctness of the analysis conclusion can be verified through simulation.