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

本研究的目的是应用整流型故障电流限制器，使用微型SMES（超导磁储能）之间的接口装置，公用事业电力网络和分布式发电机，如热电联产系统和发电机的独立电力生产商（IPP）。该系统的基本配置是基于微型SMES与二极管整流器和一个可选的逆变器，以补偿电压降和电流谐波。该系统不仅可以限制故障电流，而且还可以补偿由故障引起的电网电压降。通过仿真和实验结果验证了该系统的性能。为了降低超导线圈的电感，提出利用传统上仅用于超导线圈失超时保护目的的保护电阻与并联开关装置。通过滞环控制方案，通过与保护电阻器并联的半导体开关器件的通/断控制将线圈电流控制在指定范围内，故障电流限制器可以在不断开公用电网和分布式发电机的情况下限制故障电流更长的时间。此外，通过使用保护电阻器控制线圈电流，可以抑制电压降。通过使用保护电阻器，可以省略并联逆变器。当分布式发电机侧发生故障时，也可以限制来自电网的故障电流，该装置可以作为一种双向保护装置，在所有故障限流装置中具有最快的响应时间，并且它不需要任何故障电流检测装置，因此可以避免限流装置的不必要的操作。

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.