Study of Application Possibility on Shielding Coil System for Power System Control SMES

为了减小SMES系统中超导线圈中的电流和磁场波动，实现功率波动补偿、频率和电压稳定等电力系统控制，研究了由超导主线圈和普通屏蔽线圈并联组成的屏蔽线圈系统的可行性，提出了采用环形屏蔽线圈系统。这种类型的线圈系统具有在周围空间中的低杂散场的优点。研究了超导体的超导量、屏蔽线圈对超导体的脉动磁场和法向损耗等基本电磁特性。最后得出了实际规模超导磁储能系统的最佳结构。实验结果表明，该屏蔽线圈系统的超导体数量和系统半径与常规屏蔽线圈系统相当，并对常规屏蔽线圈中电压下降的补偿进行了研究。为了验证电压补偿器的工作情况，设计了一个由同轴螺线管型线圈（超导主线圈、屏蔽线圈和一对收集屏蔽线圈）组成的实验屏蔽线圈系统。实验屏蔽线圈系统具有与上述实际规模SMES相同的电感条件。电压补偿器由桥式变换器和控制系统组成。针对超导储能系统的各种电流模式，研究了常规屏蔽线圈的电阻和系统的性能。结果表明，电压补偿器工作正常，超导线圈电流波动基本得到抑制，并利用有限元方法研究了线圈上的电磁力。结果表明，即使在实际规模的超导磁储能系统中，线圈中的应力也足够低。

To reduce the fluctuated current and field in a superconducting coil of the SMES system for power system control such as compensation of power fluctuation and stabilizations of frequency and voltage, feasibility of a shielding coil system, which is composed of a main superconducting coil and a normal shielding coil connected in parallel was studied.Use of a toroidal type shielding coil system was proposed in this study. This type of a coil system had an advantage of low stray fields in ambient space. Fundamental electromagnetic characteristics such as superconductor quantity, fluctuated fields from the shielding coil on the superconducting one and normal loss were studied. As a result, the optimum configuration for a practical scale SMES was obtained. It is also confirmed that the superconductor quantities and the system radius of the shielding coil system were comparable to the usual type one.The compensation for the voltage decent in the normal shielding coil was studied. To verify the operation of the voltage compensator, an experimental shielding coil system, which was composed of coaxial solenoid type coils, that is, a main superconducting coil, a shielding coil and a pair of collection shielding coils. The experimental shielding coil system had the same inductance conditions as the practical scale SMES mentioned above. The voltage compensator was composed of a bridge type converter and the control system. For various current patterns of the SMES system, the resistance of the normal shielding coil and performance of the system were studied. Results showed that the voltage compensator worked properly and the fluctuation of the superconducting coil current was almost suppressed.Electromagnetic forces on the coils were also studied by the finite element method. Results showed that stress in the coils were enough low even in the practical scale SMES.