Coordinated DC Fault Ride‐Through Control for a Grid‐Forming Wind‐Storage System With VSC ‐ HVDC Integration Under Transmission Constraints

ABSTRACT Due to the complexity of wind farm environments and the particularity of DC systems, fault signals may be affected by numerous factors, which can compromise the accuracy of fault detection. Therefore, a coordinated DC fault ride‐through control scheme for a grid‐connected wind‐storage system is designed, considering transmission constraints. During an AC fault, the surplus power from the DC system is actively recovered and temporarily stored. Decoupling control of the DC voltage and the submodule (SM) capacitor voltage is achieved by adjusting the input quantity of the upper and lower bridge arm submodules and the command value of the SM capacitor voltage. The unbalanced power is optimized based on the state‐of‐charge (SOC) of the energy storage unit, and a calculation model for the grid integration level of wind power is established, taking transmission conditions into account. The characteristics of the voltage drop at the fault point, the capacitor discharge of the submodule, and the fault current loop after an HVDC line fault are analyzed. A coordination strategy between the wind turbines and the DC converter station is proposed to realize the fault ride‐through function during AC grid faults. Experimental results show that the active power rapidly decreases to approximately −0.05 per unit after the converter station detects an increase in the DC bus voltage. The unloading resistance consumes a minimum power of only 180 MW and exhibits the highest resistance value, reaching 551.1 Ω. In this case, the DC voltage fluctuation is the smallest, and the fault ride‐through performance is the best.