Wind power plant grid-forming control and influences on the power train and power system oscillations

In future power systems, wind power plants are supposed to contribute in the voltage and frequency stability of the grid. For this purpose, the control strategy of the wind power-frequency converter system needs to change from grid-following to grid-forming control. In this paper, the influence of future wind power plants equipped with the grid-forming control strategy on the wind turbine itself and the power system oscillations is studied. For this purpose, the coupled model of wind power plant and a relatively realistic model of future power system is employed, which is able to capture the internal dynamics of wind turbine power train system and its dynamic interactions with the rest of power system. It is shown how wind power plant local- and inter-area oscillations can influence/be influenced by the power system if insufficient damping is presented by wind turbines' power train system. It is shown how the variation of demand in the power grid can consistently excite wind turbine local- and inter-area modes which can cause undamped oscillations in both wind turbine power train system and the rest of power system if insufficient damping is provided by the wind turbine power train system. A test case, using 1.5 MW NREL wind turbine drivetrain, is demonstrated.