A Novel Multi-functional Solid-state Fault Current Limiter And It’s Application In The Power Grid

With the increasing requirement of power quality,the grid’s size becomes larger and its structure is being more complex.Solid State Fault Current Limiter as an important means to limit the short-circuit current has achieved large-scale application in the grid,but as technology advances,the traditional single-function SSFCL gradually being replaced by multi-functional SSFCL.When the Multi-Functional SSFCL is working in the grid,it will also bring some impacts on the normal operation of the power grid.In this paper a novel Multi-Functional Solid-State Current Limiter as an example,some research on this problem has been done from two aspects.First,the working principle of MSSFCL has been introduced.The MSSFCL presents zero impedence in normal operation and has no effect on the power grid.When the gird voltage drops or uplift,the MSSFCL can compensate the load voltage.When the short-circuit fault occurs in the system,the MSSFCL can switch to ashort-circuit limiting state to limit short-circuit current quickly.And a sequential coordination method between the MSSFCL and the rely devices under instantaneous short-circuit fault and permanent short-circuit fault is proposed.The MSSFCL limits the short-circuit current by string limiting impedance into transmission line,but it will affect the original operating characteristics of the delay protection devices.So studying the impacts on rely protection casuing by MSSFCL has great practical significance to promote the MSSFCL’s application in power system.This paper analyzes the MSSFCL’s impact on 0°wiring mode reflecting phase to phase short-circuit fault,and a new wiring mode to eliminate the impact of limiting equivalent impedance has been proposed.The filter capacitor makes the MSSFCL’s limiting filter present capacitive impedance for some certain hign-frequency harmonic,and it makes the limiting filter may occur high-frequency series resonant with transmission lines.And the high-frequency series resonant may cause the amplification of harmonic.This paper analyzes the mechanism of series resonant between limiting filter and transmission line,and a method for limiting filter selection has been proposed form perspective of the series resonance suppression.Finally,a brief introduction of main circuit and control system of the MSSFCL experimental prototype,and the experimental results demonstrate the validity and effectiveness of the MSSFCL’s limiting method.