Research on Rectifier Type Fault Current Limiter by Use of Micro-SMES (Superconducting Magnetic Energy Storage)

本研究的目的是将微型超导储能整流型故障电流限制器应用于公用事业电网与分布式发电机(如热电联产系统和独立发电商)之间的接口设备。该系统的基本配置是基于微型SMES，带有一个二极管整流器和一个可选的逆变器来补偿电压降和电流谐波。该系统不仅能限制故障电流，还能补偿电网故障引起的电压降。通过仿真和实验结果验证了该系统的性能。为了减小超导线圈的电感，提出了一种采用并联开关装置的保护电阻，该保护电阻只用于超导线圈在常规淬火情况下的保护。采用滞环控制方案，通过半导体开关器件的导通/导通控制，将线圈电流控制在规定的范围内，故障限流器可以在不断开电网和分布式发电机的情况下，将故障电流限制在更长的时间内。此外，通过使用保护电阻控制线圈电流，可以抑制电压降。利用保护电阻可以省略并联逆变器。该装置可作为其他故障限流装置中响应时间最快的双向保护装置，不需要任何故障电流检测装置，避免了限流装置的不必要操作。

The purpose of this study is to apply a rectifier type fault current limiter using Micro SMES (Superconducting Magnetic Energy Storage) for an interface device between a utility power network and a distributed generator such as a co-generation system and generator by IPPs (Independent Power Producers). The basic configuration of the system is based on Micro SMES with a diode rectifier and an optional inverter to compensate voltage drop and current harmonics. The proposed system can not only limit the fault current but also compensate voltage drop caused by the fault in the utility power network. Performance of the proposed system was verified through simulation and experimental results.In order to reduce the inductance of the superconducting coil, utilization of protection resistor, which is used only for the protection purpose of a superconducting coil in case of quenching conventionally, with a parallel switching device was proposed. Controlling the coil current within a specified range by the on/on control of the semiconductor switching device in parallel with the protection resistor by a hysteresis control scheme, the fault current limiter can limit the fault current for longer time without disconnecting the utility power network and the distributed generator. Moreover, voltage drop can be suppressed by controlling the coil current by use of the protection resistor. The parallel inverter can be omitted by use of the protection resistor. In case of fault on the distributed generator side, the fault current from the utility power network can be limited, too.This device can be used as a bi-directional protection device with fastest response time among any other fault current limiting devices and it does not require any fault current detecting device, as a result unnecessary operation of the current limiting device can be avoided.