A New Grid Connection Mode of Low Inertia Power System

Abstract

With the increase of the proportion of photovoltaic, wind power and other new energy generation in the power grid and the large amount of electric energy sent through DC transmission, the proportion of synchronous generators in the power grid continues to decline, and more and more regional power grids have gradually become low inertia power systems. Aiming at the problems of poor controllability and low stability of grid connection of low inertia power system, a new method of grid connection between low inertia power system and main network is proposed. In this method, the grid connection composite device is applied to the grid connection of low inertia power system, so as to improve the grid connection speed of low inertia power system and realize grid connection, disconnection and tie-line power flow control of low inertia power system; in order to improve the stability of the frequency response process when the grid connected composite device is applied to the low inertia scenario, the virtual synchronous machine is introduced into the receiving converter to reduce the frequency offset peak and change rate of the low inertia power system in the grid connected regulation process. Through modeling and Simulation in PSCAD/ EMTDC, it is verified that the grid connection composite device based on virtual synchronous machine can greatly improve the controllability and stability of grid connection of low inertia power system.