I. Introduction
Due to the partial flux exclusion and flux pinning, high temperature superconductors (HTSs) can be levitated above or below permanent magnets (PMs) stably, which provides a new mode for maglev [1]. Since the discovery of the HTS Maglev phenomenon, researchers have made their efforts to pursue the practical application of the HTS-PM levitation system. The world first manned HTS maglev vehicle was successfully developed in Southwest Jiaotong University [2]. In 2004, HTS maglev test vehicles were developed by IFW [3]. Levitation module for magnetic transportation system was built by an Italian group [4]. A full-scale superconducting magnetic levitation vehicle and 200 meters test line was constructed inside the campus of the Federal University of Rio de Janerio in Brazil [5]. A 45 m-long HTS Maglev ring test line was successfully developed and the evacuated tube transportation was proposed by a Southwest Jiaotong University group [6], [7]. Not only the vehicle and test line were developed, but also considerable studies have been done to investigate the performance of HTS-PM maglev system. Magnetic field distribution is studied through different configurations and arrangements of PMs [8]–[12]. Levitation and guidance force as important parameters of levitation performance were studied [13]–[18]. Stability and dynamic characteristics of maglev needed for commercial application were also studied by researchers [19]–[24].