Fast search algorithm for finding initial diffusion voltage in electro-chemical systems
First Claim
1. A method for determining an initial diffusion voltage (Vdiff)initial as a starting point when calculating a diffusion voltage Vdiff in an electrochemical cell, comprising:
- obtaining a time difference toff between a time when the cell was last turned-OFF and a time when the cell was next turned-ON;
selecting a starting diffusion voltage (Vdiff)stat based on toff;
determining a trial diffusion voltage Vdiff based on a diffusion circuit model and (Vdiff)start;
calculating an error voltage Verror=(Vdiff)−
|VOFF−
VON| where VOFF and VON are cell voltages at cell turn-OFF and cell turn-ON respectively;
repeating the foregoing determining and calculating steps using for each iteration (Vdiff)start=(Vdiff)previous+Verror until Verror is less than or equal to a first predetermined tolerance amount ε
;
storing in a memory a value of Vdiff corresponding to the condition Verror≦
ε
; and
setting (Vdiff)initial equal to the just stored value of Vdiff.
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Abstract
A method for rapidly determining an initial diffusion voltage (Vdiff)initial as a starting point in calculating a diffusion voltage in an electro-chemical cell (e.g., a battery used in an automotive vehicle) includes obtaining a time difference toff between a time when the cell was last turned-OFF and a time when the cell was next turned-ON, selecting a starting diffusion voltage (Vdiff)start based on toff, determining a trial diffusion voltage Vdiff based on a diffusion circuit model and (Vdiff)start, calculating an error voltage Verror=(Vdiff)−|VOFF−VON| where VOFF and VON are cell voltages at turn-OFF and turn-ON respectively, repeating the foregoing determining and calculating steps using for each iteration (Vdiff)start=(Vdiff)previous+Verror until Verror is less than or equal to a first predetermined tolerance amount ε, storing in a memory a value of Vdiff corresponding to the condition Verror≦ε, and setting (Vdiff)initial equal to the just stored value of Vdiff. A further diffusion voltage Vdiff is then determined using the same diffusion circuit model and the just obtained (Vdiff)initial and is advantageously used by a controller in an electric propulsion vehicle to determine a state of charge of the propulsion battery.
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Citations
20 Claims
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1. A method for determining an initial diffusion voltage (Vdiff)initial as a starting point when calculating a diffusion voltage Vdiff in an electrochemical cell, comprising:
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obtaining a time difference toff between a time when the cell was last turned-OFF and a time when the cell was next turned-ON; selecting a starting diffusion voltage (Vdiff)stat based on toff; determining a trial diffusion voltage Vdiff based on a diffusion circuit model and (Vdiff)start; calculating an error voltage Verror=(Vdiff)−
|VOFF−
VON| where VOFF and VON are cell voltages at cell turn-OFF and cell turn-ON respectively;repeating the foregoing determining and calculating steps using for each iteration (Vdiff)start=(Vdiff)previous+Verror until Verror is less than or equal to a first predetermined tolerance amount ε
;storing in a memory a value of Vdiff corresponding to the condition Verror≦
ε
; andsetting (Vdiff)initial equal to the just stored value of Vdiff. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An energy management controller for a vehicle containing a battery, comprising:
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a memory configured to store a battery condition parameter; a processor coupled to the memory and configured to; determine an initial diffusion voltage (Vdiff)initial of the battery by; obtaining a time difference toff between a time when the battery was last turned-OFF and a time when the battery was next turned-ON; selecting a starting diffusion voltage (Vdiff)start based on toff; determining a trial diffusion voltage Vdiff based on a diffusion circuit model of the battery and (Vdiff)start; calculating an error voltage Verror=(Vdiff)−
|VOFF−
VON| where VOFF and VON are battery voltages at battery turn-OFF and battery turn-ON respectively;repeating the foregoing determining and calculating steps using for each iteration (Vdiff)start=(Vdiff)previous+Verror until Verror is less than or equal to a first predetermined tolerance amount ε
;storing in the memory a value of Vdiff corresponding to the condition Verror≦
ε
; and
thensetting (Vdiff)initial equal to the just stored value of Vdiff; and
thenobtain a further diffusion voltage Vdiff based on the diffusion circuit model of the battery and the initial diffusion voltage (Vdiff)initial obtained in the setting step; and determine the battery condition parameter using the just obtained further diffusion voltage Vdiff. - View Dependent Claims (13, 14, 15, 16, 17)
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18. A hybrid electric vehicle (HEV), comprising:
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an internal combustion engine; an electric motor generator coupled to the internal combustion engine, the electric motor generator configured for use as a generator to produce a charging voltage; a battery coupled to the electric motor generator; and an engine control computer coupled to the internal combustion engine, the electric motor generator and the battery, the engine control computer comprising; a memory for storing a plurality of parameters regarding battery conditions; and a processor coupled to the memory and configured to; determine an initial diffusion voltage (Vdiff)initial by; obtaining a time difference toff between a time when the battery was last turned-OFF and a time when the battery was next turned-ON; selecting a starting diffusion voltage (Vdiff)start based on toff; determining a trial diffusion voltage Vdiff based on a diffusion circuit model of the battery and (Vdiff)start; calculating an error voltage Verror=(Vdiff)−
|VOFF−
VON| where VOFF and VON are battery voltages at battery turn-OFF and battery turn-ON respectively;repeating the foregoing determining and calculating steps using for each iteration (Vdiff)start=(Vdiff)previous+Verror until Verror is less than or equal to a first predetermined tolerance amount ε
;storing in the memory a value of Vdiff corresponding to the condition Verror≦
ε
; and
thensetting (Vdiff)initial equal to the just stored value of Vdiff; and
thenobtain a further value of diffusion voltage Vdiff based on the diffusion circuit model of the battery and (Vdiff)initial obtained in the setting step; and determine a state of charge of the battery using the just obtained further value of diffusion voltage Vdiff. - View Dependent Claims (19, 20)
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Specification