Study on High Rsponse Excitation of Superconducting Generator

超导发电机的低同步阻抗提高了电力系统的稳定性。如果SCG能够实现高响应励磁，将进一步提高电力系统的稳定性。对于高响应激励SCG，我们还有许多问题需要解决。其中一个问题是如何设计激励器。由于SCG励磁回路的时间常数很大，励磁机的容量可能很大。传统发电机采用晶闸管变流器作为励磁装置，存在着励磁容量大、无功功率大、电流谐波大等问题，本文提出了一种采用小功率电源和两个超导线圈间能量转换电路的励磁装置。其中一个用于存储，另一个是SCG的磁场绕组。电源由可控硅变换器组成，将能量提供给线圈储存。储能线圈通过能量传输电路将能量传输到励磁绕组。电源的容量是相当小的，因为它在稳定状态下仅为系统的损耗提供很小的能量。在用于高响应励磁的励磁电流的快速变化中，电流由线圈提供以用于存储。虽然从交流侧的角度来看，励磁机的容量很小，但励磁机的容量对于励磁绕组来说却很大。利用两个超导线圈进行了能量传递、阶跃响应、频率响应等基本测试。同时考虑了SCG励磁回路的特点和SCG电力系统的特点。

Low synchronous impedance of superconducting generators (SCG's) improves power system stability. If high response exitation is possible in SCG, it could improve power system stability much more. For SCG with high response exitation, wer have many problems to be solved. One of the problems is how to design the exiciter. Since time constant of field circuit of SCG is very large, the capacity of the exciter may be very large. Thyristor convertors, which are used as exciters of the conventinal generators bring some problems, that is large capacity, reactive power, current harmonics and so on. Here we propose a new method of exciter with a small power supply and an energy transfer circuit between two superconducting coils. one of them is for storage and the other is field winding of SCG. The power supply, which consists of thyristor converter, supplies energy to the coil for storage. The energy is transfered from the coil for storage to the field winding through energy transfer circuit. The capacity of the power supply is rather small since it supplies only small energy for the loss of the system in the steady state. In rapid change of the field current for high response excitation, the current is supplied from the coil for storage. Though the converer is small from a point of AC side, the exciter looks large capacity for the field winding. The fundamental tests, that is, tests for energy tranfer, step response test, frequency response test and so on, were carried out by use of two superconducting coils. They confirmed that the exciter can operate well.Furthermore, we considered characteristics of field circuit of SCG and power system characteristics of SCG.