Commutation Failure Suppression Strategy Considering Critical Extinction Angle Variation Characteristics of HVDC Converter

Introduction: The critical extinction angle of the HVDC converter is closely related to commutation failure and varies with the operating conditions. Existing research ignores the dynamic variation characteristics of the critical extinction angle, which will weaken the effect of the commutation failure suppression strategy. Considering the dynamic variation characteristics of the critical extinction angle, a commutation failure suppression strategy by dynamically compensating the extinction angle is proposed to improve the effect of commutation failure suppression. Methods: Firstly, this paper analyzes the influencing factors of the critical extinction angle, and establishes a calculation model of the critical extinction angle. Then, based on the proposed model, the influence of the critical extinction angle variation on the commutation failure process is analyzed. Considering the dynamic variation characteristics of the critical extinction angle during AC short-circuit fault, a commutation failure suppression strategy based on extinction angle compensation is proposed. Results: The proposed strategy can improve the suppression effect of commutation failure under different operating conditions, decrease the drop of AC voltage, and increase the recovery speed of DC power. Discussion: The proposed control strategy takes into account the dynamic variation of the critical extinction angle, enhances the suppression effect on commutation failure in HVDC systems, and improves the grid stability in modern power systems. Conclusion: Commutation failure is affected by the dynamic variation characteristics of the critical extinction angle. The proposed strategy considers the characteristics that can accelerate the fault recovery and improve the commutation failure resistance ability.