Optimal Scheduling Method for Multi-infeed Receiving-End Power Grids Under Frequency Deviation and Voltage Stiffness Constraints

The ultra high voltage direct current (UHVDC) transmission system based on line commutation converters (LCCs) is the main technical means for long-distance and high-capacity transmission. To avoid DC power reduction events caused by insufficient system stability margin, an optimal scheduling method for multi-infeed receiving-end power grids considering stability constraints is proposed. Firstly, based on the primary frequency regulation model, the frequency stability constraint for the system’s maximum DC transmission power is derived. Secondly, a voltage stiffness index is proposed to evaluate the recovery characteristics of the HVDC commutation failures, and based on this index, the voltage stability constraint is established. Then, considering the frequency and voltage stability constraints as well as various operational constraints, an optimal scheduling model is established for the multi-infeed receiving-end power grids. Finally, the effectiveness of the proposed method is verified through testing on a modified IEEE 39-bus system. The results show that the proposed method can meet the system frequency and voltage stability requirements by changing the unit commitment and DC power, thus avoiding the safety and stability risks caused by strong DC and weak AC.