New control approach for blackstart capability of full converter wind turbines with direct voltage control

This paper presents a new control approach for load pick and restoration of power systems by full converter based wind turbines. In such blackstart scenarios, batteries or other storage devices that can establish frequency or balance generation and consumption of power are not necessarily available. Therefore, a so-called grid forming control scheme is required. The control scheme used in this paper is based on direct voltage control. To balance the generation of power with the load demand, an intermediate circuit voltage control is used. Based on this concept, an alternative speed-power controller is designed to replace the MPPT based speed control in the process of blackstart and restoration. Furthermore, the definition of the frequency in an island grid is discussed. The overall control approach is presented and evaluated based on electromagnetic transient type simulations, involving islanding, load pick up, restoration, and resynchronization.