Bidirectional power converter for balancing state of charge among series connected electrical energy storage units

Abstract

A system is provided for balancing state of charge among plural series connected electrical energy storage units that includes a power converter that selectively couples to an individual storage unit of the a string of electrical energy storage units and transfers energy by bidirectionally between the individual storage unit and the string of storage units.

1 - 22 . (canceled) 
   
   
       23 . A system, comprising:
 a string of electrical energy storage units having a first end and a second end; and   a buck-boost dc-dc power converted coupled simultaneously to a selected portion of the string of electrical energy storage units and to the first and second ends of the string of electrical energy storage units, the power converter being configured to transfer energy bidirectionally between the selected portion of the string of storage units and the end points of the string of storage units,   wherein the power converter is configured to transfer energy at a controllable rate of transfer, and   the power converter comprises:   an up-converter configured to transfer energy from the selected portion of the string of storage units to the end points of the string of storage units; and   a down-converter configured to transfer energy from the string of storage units to the selected portion of the string of storage units.   
   
   
       24 . The system of  claim 23 , wherein the power converter is configured to monitor voltage and current data of the selected portion of the string of storage units resulting from a transfer of energy. 
   
   
       25 . The system of  claim 23 , wherein the power converter is configured to transfer units of energy between the selected portion of the string of storage units and the end points of the string of storage units. 
   
   
       26 . The system of  claim 23 , wherein the power converter comprises:
 a primary inductor;   a first secondary inductor magnetically coupled to the primary inductor;   a first switch selectively coupling the selected portion of the string of storage units to the primary inductor; and   the first secondary inductor coupling to an output capacitor;   the output capacitor coupled in parallel to the string of storage units.   
   
   
       27 . The system of  claim 23 , further comprising:
 a primary inductor;
 a first secondary inductor magnetically coupled to the primary inductor; 
 a switch selectively coupling the first secondary inductor to the end points of the string of storage units, and configured to transfer energy from the string of storage units to charge the first secondary inductor when the switch is on, and to discharge energy into the primary inductor and charging the selected portion of the string of individual storage units when the switch is of. 
   
   
   
       28 . The system of  claim 23 , wherein a common transfer is configured to serve as the up-converter and the down converter. 
   
   
       29 . The system of  claim 23 , wherein each storage unit is a storage cell. 
   
   
       30 . The system of  claim 23 , wherein each storage unit is a battery module having a string of storage units. 
   
   
       31 . The system of  claim 23 , wherein a battery pack comprises a string of one or more storage units.