Design and Verification of High-Voltage Stator for Grid-Directly-Connected Superconducting Synchronous Condenser

To achieve a superconducting synchronous condenser (SSC) directly connected to the power grid without the need for a step-up transformer, this article proposes a high-voltage stator topology incorporating cable windings and nonmagnetic teeth. The research addresses key issues such as the topology of cable windings, bending radius verification, slot design, and the structural design of the high-voltage stator. Based on voltage breakdown tests of cross-linked polyethylene (XLPE) sheet samples and the characteristics of the stator windings, an insulation scheme for 35 kV XLPE cables is designed. In addition, a stepped insulation scheme for cable windings is proposed. An electromagnetic design process for the high-voltage stator is outlined, and a field-circuit coupled model is developed for the grid-directly-connected SSC, completing the electromagnetic design for a 30 Mvar, 35 kV SSC. Temperature field simulations for the high-voltage stator are performed, validating the preliminary feasibility of the high-voltage stator from both electromagnetic design and ventilation cooling perspectives. Finally, a prototype of the cable-winding synchronous condenser is developed and tested, and through the withstand voltage test of the cable windings, the preliminary feasibility of the grid-directly-connected SSC is confirmed.