US 11,056,883 B1
System and method for implementing a zero-sequence current filter for a three-phase power system
Nicholas Benavides, Zionsville, IN (US); Brett Robbins, Indianapolis, IN (US); and Thomas Craddock, Indianapolis, IN (US)
Assigned to Switched Source PB LLC, Vestal, NY (US)
Filed by Switched Source PB LLC, Vestal, NY (US)
Filed on Jan. 13, 2021, as Appl. No. 17/148,136.
Application 17/148,136 is a continuation of application No. 16/864,094, filed on Apr. 30, 2020.
Int. Cl. H02J 3/18 (2006.01); H01F 30/12 (2006.01)
CPC H02J 3/1857 (2013.01) [H01F 30/12 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A system for actively controlling zero-sequence current in a three-phase power distribution network having a phase A, a phase B, a phase C, and a neutral, the system comprising:
a transformer comprising:
a first primary winding comprising a first primary winding dot terminal and a first primary winding non-dot terminal;
a first secondary winding comprising a first secondary winding dot terminal and a first secondary winding non-dot terminal, wherein the first primary winding and the first secondary winding share a first common magnetic flux path;
a second primary winding comprising a second primary winding dot terminal and a second primary winding non-dot terminal;
a second secondary winding comprising a second secondary winding dot terminal and a second secondary winding non-dot terminal, wherein the second primary winding and the second secondary winding share a first common magnetic flux path;
a third primary winding comprising a third primary winding dot terminal and a third primary winding non-dot terminal; and
a third secondary winding comprising a third secondary winding dot terminal and a third secondary winding non-dot terminal, wherein the third primary winding and the third secondary winding share a first common magnetic flux path;
wherein the third primary winding non-dot terminal is operatively coupled to the first secondary winding non-dot terminal;
wherein the first primary winding non-dot terminal is operatively coupled to the second secondary winding non-dot terminal;
wherein the second primary winding non-dot terminal is operatively coupled to the third secondary winding non-dot terminal;
wherein the first secondary winding dot terminal, the second secondary winding dot terminal, and the third secondary winding dot terminal are operatively coupled to the neutral;
a first Cascade Multilevel Modular Inverter (CMMI) comprising a first CMMI first terminal and a first CMMI second terminal, wherein the first CMMI first terminal is operatively coupled to phase A, and the first CMMI second terminal is operatively coupled to the first primary winding dot terminal;
a second CMMI comprising a second CMMI first terminal and a second CMMI second terminal, wherein the second CMMI first terminal is operatively coupled to phase B, and the second CMMI second terminal is operatively coupled to the second primary winding dot terminal;
a third CMMI comprising a third CMMI first terminal and a third CMMI second terminal, wherein the third CMMI first terminal is operatively coupled to phase C, and the third CMMI second terminal is operatively coupled to the third primary winding dot terminal; and
a controller operatively coupled to the first CMMI, the second CMMI, and the third CMMI, the controller operable to:
a) modulate a first voltage produced by the first CMMI to control a first equivalent impedance between phase A and the neutral;
b) modulate a second voltage produced by the second CMMI to control a second equivalent impedance between phase B and the neutral; and
c) modulate a third voltage produced by the third CMMI to control a third equivalent impedance between phase C and the neutral.