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Project

AC Connection of Wind Farms to Transmission System: from Grid-Following to Grid-Forming

Wind power plants (WPPs) constitute a significant share of the renewable energy sources interfaced to the grid with a power electronic converter. Till now, nearly all of these converters are connected to the grid in grid-following mode. Over the next years, at least some of them, are expected to switch to grid-forming mode.

The grid-forming control differs from a classical grid-following control. Therefore, in order to make a Type-4 wind turbine function in grid-forming mode, a significant modification in the control configuration of the back-to-back converter is required. This appropriate control modification in turn creates a strong coupling between the grid-forming converter and the mechanical part of the wind turbine. This coupling induces several negative effects on the operation of the wind turbine. The major effect is a fast variation of the generator’ electromagnetic torque, resulting in increased torsional vibrations induced in the wind turbine drivetrain. Therefore, to mitigate this effect, the impact of the grid-forming control on the wind turbine is investigated and possible solutions for vibration damping are proposed.      

A grid-forming WPP is an interesting mean to improve power system stability. However, to analyze a grid-forming WPP connected to a transmission system, the use of its dynamic equivalent model is typically required. Standard equivalent models cannot be reliable in all possible wind conditions. For this reason, in this thesis, the aggregation of a WPP is developed by taking into account the heterogeneous nature of the wind distribution within a WPP. In addition, an algorithm that recommends the equivalent model to be used in each wind condition is proposed. The verification of the aggregation methodology and the recommendation algorithm is carried out on the case study of an existing WPP. 

Date:12 Apr 2019 →  8 Dec 2022
Keywords:converter, offshore wind farm, grid following, grid forming, wind energy, transmission grid
Disciplines:Renewable power and energy systems engineering
Project type:PhD project