Reluctance-based circuit for high temperature superconductor generator lumped-parameter model

The present work addresses the ongoing development of a mesh-based magnetic equivalent circuit (MEC) to estimate the magnetic flux distribution in a superconducting hybrid rotating synchronous machine, superconducting (SC) rotor and conventional stator. The MEC is to be integrated in an existing thermoelectric lumped-parameter machine model for the transient simulation of High Temperature Superconductor (HTS) field coil synchronous generator (SG) in the dq0 frame of reference. It will allow the inclusion of the magnetic flux density inside the definition of the non-linear resistance of the superconductor in addition to the already-present temperature and current. The objective is to gain further accuracy on the coupled thermal and electromagnetic behavior of superconducting hybrid machines during partial or total loss of the superconducting state. In the present work, the MEC is benchmarked against a Finite Element Model (FEM). It is shown that the MEC can provide proper magnitude of the magnetic flux density over the HTS winding achieving a good estimation of the magnetic response of the field winding by taking into account the penetration of current within the superconductor. The case study is a 100-MVA hydroelectric HTS field coil SG considering a field current ramp.