Modeling of Dynamic Control Error and Emergency Frequency Control for Direct-Drive PMSG-Based Wind Turbine Under Grid Fault

The utilization of direct-drive permanent magnet synchronous generator-based wind turbine (DPMWT) is prevalent in mitigating unbalanced power during fault process. However, sudden variations in the magnitude and phase angle of grid voltage during grid faults may result in the phase-locked loop transient response (PLTR) of DPMWT. The PLTR changes the output characteristics of DPMWT through converter control loop. This alteration incorporates dynamic control errors and presents potential hazards to the transient frequency of power system. Therefore, the dynamic control error resulting from PLTR under the three-phase fault is found, and an emergency frequency control method for DPMWT under the three-phase fault is proposed. The quantification method for PLTR under the three-phase fault is proposed, and the conduction paths of PLTR within the converter control loop are analyzed. The mechanism of dynamic control error of DPMWT under the three-phase fault is analyzed, and the calculation method for dynamic control error is further proposed. Moreover, the transient frequency characteristics of the power system when affected by dynamic control error are analyzed, and the emergency frequency control method for DPMWT based on the compensation of dynamic control error is put forward. The effectiveness of the proposed method is verified by case studies.