Controlling voltage in electrical power distribution grid

Abstract

Control of grid voltage in a power grid. A power transformer converts alternating current (AC) electrical power at a higher voltage on the primary leads to AC electrical power at a lower grid voltage on the secondary leads. An auxiliary AC/AC power converter converts input AC electrical power at the input conductors to output AC electrical power at the output conductors, The auxiliary AC/AC power converter converts substantially less electrical power than the AC electrical power converted by the power transformer. The secondary leads of the power transformer are series-connected to the output conductors of the auxiliary AC/AC power converter. Input conductors of the auxiliary AC/AC power converter are parallel-connected to either (i) the primary leads of the power transformer, or (ii) the secondary leads of the power transformer. The output alternating voltage of the auxiliary AC/AC power converter adds to the output alternating voltage of the power transformer to control the grid voltage in the power grid.

What is claimed is: 
     
         1 . A method for controlling grid voltage in a power grid including a power transformer with primary leads and secondary leads, wherein the power transformer is configured to convert alternating current (AC) electrical power at a higher voltage on the primary leads to AC electrical power at a lower grid voltage on the secondary leads, the method comprising:
 providing a first auxiliary AC/AC power converter with first input conductors and first output conductors, wherein the first auxiliary AC/AC power converter is configured to convert input AC electrical power at the first input conductors to output AC electrical power at the first output conductors, wherein the first auxiliary AC/AC power converter is configured to convert substantially less electrical power than the AC electrical power converted by the power transformer;   series-connecting the secondary leads of the power transformer to the first output conductors of the first auxiliary AC/AC power converter; and   parallel-connecting first input conductors of the first auxiliary AC/AC power converter to the primary leads of the power transformer;   wherein the output alternating voltage of the first auxiliary AC/AC power converter adds to the output alternating voltage of the power transformer to control the grid voltage in the power grid.   
     
     
         2 . The method of  claim 1 , wherein the switches are configurable to reverse connection between the first input conductors of the auxiliary transformer. 
     
     
         3 . The method of  claim 1 , wherein the power transformer includes three or more primary leads and three or more corresponding secondary leads configured to output different phases, and wherein the first output conductors of the first auxiliary AC/AC power converter are configured to output different phases corresponding to the phases of the multiple secondary leads of the power transformer. 
     
     
         4 . The method of  claim 1 , further comprising:
 sensing at least one sensed electrical parameter output after the series-connection of the secondary leads of the power transformer to the first output conductors of the first auxiliary AC/AC power converter, wherein the at least one sensed electrical output parameter is selected from the group consisting of: total alternating voltage of the first auxiliary AC/AC power converter summed with the output alternating voltage of the power transformer, current and phase.   
     
     
         5 . The method of  claim 4 , further comprising:
 providing a control signal to the first auxiliary AC/AC power converter responsive to the at least one sensed parameter.   
     
     
         6 . The method of  claim 1 , wherein the first auxiliary AC/AC power converter is an auxiliary transformer and wherein the first input conductors of the auxiliary transformer are connectible through a plurality of switches to the power transformer, the method further comprising:
 providing a control signal to the switches responsive to the at least one sensed parameter.   
     
     
         7 . The method of  claim 1 , further comprising:
 receiving remotely a control parameter; and   provide a monitoring signal remotely with respect to status of the controlled grid voltage.   
     
     
         8 . The method of  claim 1 , further comprising:
 providing a second auxiliary AC/AC power converter with second input conductors and second output conductors, wherein the second auxiliary AC/AC power converter is configured to convert input AC electrical power at the second input conductors to output AC electrical power at the second output conductors, wherein the second auxiliary AC/AC power converter is configured to convert substantially less electrical power than the AC electrical power converted by the power transformer;   series-connecting the secondary leads of the power transformer to the second output conductors of the second auxiliary AC/AC power converter; and   parallel-connecting second input conductors of the second auxiliary AC/AC power converter to the primary leads of the power transformer;   wherein the output alternating voltage of the second auxiliary AC/AC power converter adds to the output alternating voltage of the power transformer to control the grid voltage in the power grid.   
     
     
         9 . The method of  claim 8 , wherein the first and second AC/AC power converters include first and second auxiliary transformers which share a magnetic core. 
     
     
         10 . A system for controlling grid voltage in a power grid, the system comprising:
 a power transformer with primary leads and secondary leads, wherein the power transformer is configured to convert alternating current (AC) electrical power at a higher voltage on the primary leads to AC electrical power at a lower grid voltage on the secondary leads;   a first auxiliary AC/AC power converter with first input conductors and first output conductors, wherein the first auxiliary AC/AC power converter is configured to convert input AC electrical power at the first input conductors to output AC electrical power at the first output conductors, wherein the first auxiliary AC/AC power converter is configured to convert substantially less electrical power than the AC electrical power converted by the power transformer;   wherein the secondary leads of the power transformer are series-connected to the first output conductors of the first auxiliary AC/AC power converter;   wherein the first input conductors of the first auxiliary AC/AC power converter are parallel-connected to the primary leads of the power transformer;   wherein the output alternating voltage of the first auxiliary AC/AC power converter adds to the output alternating voltage of the power transformer to control the grid voltage in the power grid.   
     
     
         11 . The system of  claim 10 , wherein the first auxiliary AC/AC power converter is an auxiliary transformer and wherein the first input conductors of the first auxiliary transformer are connectible through a plurality of switches to the primary leads of the power transformer, wherein the switches are configurable to reverse connection between the first input conductors of the auxiliary transformer. 
     
     
         12 . The system of  claim 10 , wherein the power transformer includes three or more primary leads and three or more corresponding secondary leads configured to output different phases, and wherein the first output conductors of the first auxiliary AC/AC power converter are configured to output different phases corresponding to the different phases of the multiple secondary leads of the power transformer. 
     
     
         13 . The system of  claim 10 , further comprising:
 a sensor configured to sense at least one sensed electrical parameter output after the series-connection of the secondary leads of the power transformer to the first output conductors of the first auxiliary AC/AC power converter, wherein the at least one sensed electrical output parameter is selected from the group consisting of: total alternating voltage of the first auxiliary AC/AC power converter summed with the output alternating voltage of the power transformer, current and phase.   
     
     
         14 . The system of  claim 11 , further comprising:
 a control module operatively connected to the sensor, wherein the control module is configured to provide a control signal to the first auxiliary AC/AC power converter responsive to the at least one sensed parameter.   
     
     
         15 . The system of  claim 11 , further comprising:
 a control module operatively connected to the sensor, wherein the control module is configured to provide a control signal to the switches responsive to the at least one sensed parameter.   
     
     
         16 . The system of  claim 10 , further comprising
 a communications module configured to receive remotely a control parameter and provide a monitoring signal remotely with respect to the status of the system for controlling grid voltage in the power grid.   
     
     
         17 . The system of  claim 10 , further comprising:
 a second auxiliary AC/AC power converter with second input conductors and second output conductors, wherein the second auxiliary AC/AC power converter is configured to convert input AC electrical power at the second input conductors to output AC electrical power at the second output conductors, wherein the second auxiliary AC/AC power converter is configured to convert substantially less electrical power than the AC electrical power converted by the power transformer;   wherein the secondary leads of the power transformer are series-connected to the second output conductors of the second auxiliary AC/AC power converter;   wherein the second input conductors of the second auxiliary AC/AC power converter are parallel-connected to the primary leads of the power transformer;   wherein the output alternating voltage of the second auxiliary AC/AC power converter adds to the output alternating voltage of the power transformer to control the grid voltage in the power grid.   
     
     
         18 . The system of  claim 17 , wherein the first and second AC/AC power converters include first and second auxiliary transformers which share a magnetic core. 
     
     
         19 . A system for controlling grid voltage in a power grid, the system comprising:
 a power line with input leads and output leads, wherein the power line carries alternating current (AC) electrical power between the input and output leads;   an auxiliary AC/AC power converter with input conductors and output conductors, wherein the auxiliary AC/AC power converter is configured to convert input AC electrical power at the input conductors to output AC electrical power at the output conductors, wherein the auxiliary AC/AC power converter is configured to convert substantially less electrical power than the AC electrical power carried by the power line;   wherein the output leads of the power line are series-connected to the output conductors of the auxiliary AC/AC power converter;   wherein the input conductors of the auxiliary AC/AC power converter are parallel-connected to the input leads of the power line;   wherein the output alternating voltage of the auxiliary AC/AC power converter adds to the output alternating voltage of the power line to control the grid voltage in the power grid.   
     
     
         20 . The system of  claim 19 , wherein the auxiliary AC/AC power converter is an auxiliary transformer and wherein the input conductors of the auxiliary transformer are connectible through a plurality of switches to the input leads of the power line.