Current source inverter differential protection method

Current source inverter differential protection method, relay device current transformer current source is protected on both sides of the current transformer CT secondary side current is sampled to obtain the line-side phase current INA, INB, Inc is an, and the outlet-side three-phase current iMa, iMb, iMc; digital rectified to obtain the equivalent input current iN line-side and output-side current iM of the outlet; press both sides of the CT current ratio conversion iN, after iM of differencing, to obtain transient differential current Idiff; press both sides of the CT current ratio conversion iN, iM of the averaged to obtain transient braking current IRES; function through an arithmetic mean or a root mean square conversion, and the obtained differential current Idiff the Ires braking current; and finally by Idiff Ires implemented according to conventional fold line differential protection ratio braking characteristic variation or slope percentage restraint characteristic. The present invention solves the current-source converter depending sides current differential protection frequencies can not be a problem, the secondary circuit connection is simple, convenient protection setting value, ease of application.