OTCtable
One time-constant table-based equivalent-circuit model of a battery
Description
Connections
Variables
Basic Parameters
Basic Thermal Parameters
Voc Parameters
General Parameters
References
The EquivCircuit.OTCtable component is an equivalent-circuit model of a generic battery. The open-circuit voltage depends on the state-of-charge (SoC) and, optionally, the temperature of the cell, based on an interpolation table. The transient response is modeled by an SoC-dependent resistor-capacitor network.
Open Circuit Cell Voltage
The open-circuit cell voltage (Voc) is dependent on the state-of-charge and, optionally, the cell temperature.
If the Use temperature boolean parameter is false, then Voc depends only on the state-of-charge, using interpolation of the 1D Table parameter; otherwise Voc depends on SoC and the cell temperature, using interpolation of the the 2D Table parameter.
The Data Source parameter selects whether the interpolation table is defined inline, as an attachment, or as an external file.
The first column of the 1D Table is the state-of-charge (SoC), which varies from 0 (fully discharged) to 1 (fully charged).
A selected column of the table contains the open-circuit voltage data corresponding to the SoC in column 1. If Data Source is inline, the selected column is the second column, otherwise it is the value of the Column parameter.
The Skip rows parameter specifies the number of rows, starting with the first, to skip to get to the actual data.
The first column of the 2D Table is the SoC. The first row of the 2D Table is the temperature in degrees Celsius. The bulk of the content of the table specifies Voc at the corresponding SoC and temperature.
Thermal Effects
Select the thermal model of the battery from the heat model drop-down list. The available models are: isothermal, external port, and convection.
Isothermal
The isothermal model sets the cell temperature to a constant parameter, Tiso.
External Port
The external port model adds a thermal port to the battery model. The temperature of the heat port is the cell temperature. The parameters mcell and cp become available and are used in the heat equation
mcellcpdTcelldt=Pcell−Qcell
Qflow=ncellQcell
Pcell=icellvcell−voc
where Pcell is the heat generated in each cell, including chemical reactions and ohmic resistive losses, Qcell is the heat flow out of each cell, and Qflow is the heat flow out of the external port.
Convection
The convection model assumes the heat dissipation from each cell is due to uniform convection from the surface to an ambient temperature. The parameters mcell, cp, Acell, h, and Tamb become available, as does an output signal port that gives the cell temperature in Kelvin. The heat equation is the same as the heat equation for the external port, with Qcell given by
Qcell=hAcellTcell−Tamb
Capacity
The capacity of a cell can either be a fixed value, CA, or be controlled via an input signal, Cin, if the use capacity input box is checked.
Resistance
The resistance of a cell can either be a fixed value, Rcell, or be controlled via an input signal, Rin, if the use resistance input box is checked. This resistance is in addition to the resistance of the equivalent circuit.
State of Charge
A signal output, soc, gives the state-of-charge of the battery, with 0 being fully discharged and 1 being fully charged.
The parameter SOCmin sets the minimum allowable state-of-charge; if the battery is discharged past this level, the simulation is either terminated and an error message is raised, or, if the allow overdischarge parameter is true, a warning is generated. A similar effect occurs if the battery is fully charged so that the state of charge reaches one; the simulation is terminated unless allow overcharge is true.
The parameter SOC0 assigns the initial state-of charge of the battery.
Name
Type
Modelica ID
p
Electrical
Positive pin
n
Negative pin
soc
Real output
State of charge [0..1]
Cin
Real input
Sets capacity of cell, in ampere hours; available when use capacity input is true
Rin
Sets resistance of cell, in ohms; available when use cell resistance input is true
Units
Tcell
K
Internal temperature of battery
i
A
Current into battery
v
V
Voltage across battery
Default
Ncell
1
Number of cells, connected in series
CA
A·h
Capacity of cell; available when use capacity input is false
C
SOC0
Initial state-of-charge [0..1]
SOCmin
0.02
Minimum allowable state-of-charge
Rcell
0.005
Ω
Fixed cell resistance, if use cell resistance input is false
allow overcharge
false
True allows simulation to continue with 1<SoC
allow_overcharge
allow overdischarge
True allows simulation to continue with SoC<SoCmin
allow_overdischarge
use capacity input
True allows enables the Cin input port
useCapacityInput
use cell resistance input
True allows enables the Rin input port
useResistInput
Tiso
298.15
Constant cell temperature; used with isothermal heat model
cp
750
JkgK
Specific heat capacity of cell
mcell
0.014
kg
Mass of one cell
h
100
Wm2K
Surface coefficient of heat transfer; used with convection heat model
Acell
0.0014
m2
Surface area of one cell; used with convection heat model
Tamb
Ambient temperature; used with convection heat model
Use temperature
True means use the 2D table
VocUseTemp
Data Source
Selects whether the table is inline, an attachment, or a file
VocDataSource
Data
Name of file or attachment
VocData
Table 1D
Inline 1D interpolation table
VocTable1D
Table 2D
Inline 2D interpolation table
VocTable2D
Column
Specifies data column; used with 1D attachment/file
VocColumn
Skip rows
Specifies rows to skip; used with 1D attachment/file
VocSkipRows
Rout
1D interpolation table for series resistance
Rtc
1D interpolation table for time-constant resistance
Ttc
s
1D interpolation table for time-constant duration
A 1D interpolation table is a two-column Matrix. The first column is the state-of-charge, sorted, with low value (0) first. The second column is the corresponding parameter value at that state-of-charge.
[1] Chen, M. and Rincón-Mora, G.A., Accurate electrical battery model capable of predicting runtime and I-V performance, IEEE Transactions of Energy Conversion, Vol. 21, No. 2, 2006.
See Also
Battery Library Overview
Equivalent Circuit Overview
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