Robust grid forming control for black start operation of diode rectifier based wind power plants

Black start capability of off-shore wind power plants is an important feature to reduce the number of traditional power plants required for robust system operation. The impedance seen by each wind turbine shows a large variation during the complete black start procedure, normal operation and during faults. This paper proposes a controller design methodology for the voltage control of grid-forming wind turbines based on μ-synthesis optimisation that ensures the stability of the wind power plant during all the considered modes of operation (black start operation, normal operation and faults). The use of μ-synthesis optimisation leads to the optimal controller in terms of robustness and performance for all the impedance variations that occur during the operation of the wind power plant, as is confirmed by the obtained results. The results include Matlab simulations for a limited number of wind turbines and a validation on a real-time co-simulation of a detailed large scale wind power plant, including detailed aeroelastic, mechanical, electric and power electronic models of the complete wind power plant.