I. Introduction
With the characteristic of the high-efficiency energy storage, quick power response in four quadrants, superconducting magnetic energy storage (SMES) system can be utilized to cope with issues of the integration of renewable energy, the stability operation of power system, and the improvement of power quality [1], [2], etc. The basic principle of SMES is to store magnetic field energy by a superconducting magnet. Generally, the magnet is connected to the AC grid through a power conditioning system (PCS), which can realize the bidirectional power exchange. According to different mechanisms and structures of the PCS system, SMES can be connected with the ac grid in parallel or in series, which can realize functions such as dynamic power compensation [3]–[5], dynamic voltage compensation [6], [7], power quality condition [8], and power flow control [9], [10]. In various applications, no matter what topology the PCS adopts, it usually uses high-frequency power electronic converters. Therefore, the superconducting magnet will suffer the high-frequency pulsewidth modulation (PWM) voltage output by the PCS. Furthermore, the PWM pulse voltage distributes in the windings of the magnet unevenly, which will increase the insulation pressure of the magnet and further influence the security of the magnet [11], [12]. As a matter of fact, the generation, transmission, and distribution of PWM pulse voltage of SMES system is the synthetic interaction between the power system requirement, PCS control, and the magnet. Therefore, the design of SMES system should consider the interaction between the components, and the influence of PWM pulse voltage on SMES magnet.