Adaptive VSG Control Scheme for Large Scale Wind Farms to Improve Frequency Response Characteristics

Abstract

The frequency support capability of the power grid is weakened with the increase of wind power penetration. To address this problem, wind farms (WFs) are required to participate in grid frequency response by power system operators. The WFs can participate in both inertia response (IR) and primary frequency regulation (PFR) by adopting conventional virtual synchronous generation (VSG) scheme that has fixed control parameters. Such design cannot accommodate different operation conditions of WFs and results in insufficient utilization of the energy stored in the VSG controlled WFs (VSG-WFs) for frequency response. In order to make full use of the energy stored in wind turbines (WTs) for improving frequency response characteristics, an adaptive virtual synchronous generator (AVSG) control scheme is proposed in this paper. The reserved power is used to support IR. Compared with the conventional VSG scheme, the wind turbine (WT) rotor kinetic energy (KE) in the WFs can be utilized more sufficiently by adjusting the inertia coefficient according to both WT rotor speed and grid frequency. The effectiveness of the proposed scheme is verified by simulations. It can be seen that during the same frequency event, both the rate of change of frequency (RoCoF) and frequency nadir of the power grid are improved with AVSG scheme compared with conventional VSG scheme.