Online Identification Method of High Voltage AC Power Grid Strength Based on Disturbance of Control System of MMC Station

The decrease of the strength of AC power grid will adversely affect the stable operation of the modular multi-level converter HVDC (MMC-HVDC) transmission system. To avoid the potential safe and stable operation risk brought by the weak AC power grid to the AC/DC system, and to realize the rapid online monitoring of the AC power grid strength under complex and changeable working conditions, this paper proposes an online identification method of strength based on disturbance of Control System of MMC Station. Firstly, the principle and identification method of disturbance and calculation method of AC power grid are introduced from the theoretical perspective. Then the influence of the frequency variation characteristics of the transmission line and the amount of reactive power injection on the accuracy of the power grid strength identification results are introduced respectively. Finally, the feasibility of the proposed method and the constraint of the identification accuracy are verified in simulation.