An Improved End-Winding Leakage Inductance Calculation Method Based on Frozen Permeability for Large Synchronous Condenser

New and large synchronous condensers (SC) are required to improve the sub-transient voltage stability on the high voltage DC transmission, and the leakage inductance accurate calculation of SC is vital to meet the grid requirements. An improved end leakage inductance calculation method based on frozen permeability was proposed. Firstly, the end leakage inductance separation method by using 2D/3D finite element analysis was presented. Secondly, according to the actual structure of a 300 Mvar SC, 2D and 3D end FEA models were established respectively to analyze the magnetic saturation distribution in different operational states. Finally, the end leakage inductance under the different operation conditions was calculated and compared with the conventional method. The results show that to calculate the end-winding leakage inductance of SC, the effect of magnetic saturation and the rotor position should be considered, especially in the transient condition, and the saturation distribution of d and q-axis are also different under different working conditions.