Modelling of AC-DC Voltage Control Coupling and Adaptive Fault Ride-Through Method for VSC-HVDC Integrated Wind Farms

During grid fault, the voltage source converter-based high voltage direct current (VSC-HVDC) integrated wind farms should effectively support the grid voltage while ensuring the integrated system security. Existing studies have neglected the AC-DC voltage control coupling caused by the sudden change in the grid's complex impedance due to the fault transition impedance, which may lead to transient DC overvoltage, poor elevation of grid voltage, or active power loss of wind farms. A faulted grid equivalent model based on the virtual fault is established, and the mechanism of AC-DC voltage control coupling of the integrated system caused by the complex impedance of the faulted grid is found. A coupling model of the grid-connection bus voltage of the integrated system, maximum DC voltage deviation, and active power of the wind-end converter is established, and the quantification method for the maximum grid voltage support capability of the integrated system is proposed. Finally, the adaptive symmetrical fault ride-through method balancing between AC-DC voltage control is proposed. Through simulation verification, the proposed method can maximize the grid voltage elevation and minimize the active power loss of wind farms while avoiding DC overvoltage and the steady-state AC overcurrent of grid-end converter under the premise.