Buildings.Electrical.DC.Storage.BaseClasses

Base models for battery package

Information

This package contains base classes that are used to construct the models in Buildings.Electrical.DC.Storage.

Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).

Package Content

Name	Description
Charge	Model to compute the battery charge

Buildings.Electrical.DC.Storage.BaseClasses.Charge

Model to compute the battery charge

Buildings.Electrical.DC.Storage.BaseClasses.Charge

Information

This model represents the charge/discharge mechanism of a battery.

This model two parameters η_CHA and η_DIS that represent the efficiency during the charge and discharge of the battery.

The model given the power P that should be provide or taken from the battery and compute the actual power flowing through the battery as

Equation	Condition
P_actual = P η_CHA	P ≥ 0
P_actual = P (2 - η_DIS)	P < 0

The actual power is then used to compute the variation of the state of charge SOC. The state of charge is the state variable of this model and is a real value between 0 and 1.

d SOC / dt = P_actual

Note:The input power P has to be controlled in order to avoid the state of charge SOC exceeding the range between 0 and 1.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Efficiency	etaCha	0.9	Efficiency during charging [1]
Efficiency	etaDis	0.9	Efficiency during discharging [1]
Real	SOC_start	0.1	Initial state of charge [1]
Energy	EMax	EMax(min=0, displayUnit="kWh")	Maximum available charge [J]

Connectors

Type	Name	Description
input RealInput	P	[W]
output RealOutput	SOC	State of charge

Modelica definition

model Charge "Model to compute the battery charge" extends Modelica.Blocks.Icons.Block; parameter Modelica.SIunits.Efficiency etaCha(max=1) = 0.9 "Efficiency during charging"; parameter Modelica.SIunits.Efficiency etaDis(max=1) = 0.9 "Efficiency during discharging"; parameter Real SOC_start(min=0, max=1, unit="1")=0.1 "Initial state of charge"; parameter Modelica.SIunits.Energy EMax(min=0, displayUnit="kWh") "Maximum available charge"; Modelica.SIunits.Power PAct "Actual power"; Modelica.Blocks.Interfaces.RealInput P(final quantity="Power", final unit="W"); Modelica.Blocks.Interfaces.RealOutput SOC(min=0, max=1) "State of charge"; protected Boolean underCharged "Flag, true if battery is undercharged"; Boolean overCharged "Flag, true if battery is overcharged"; initial equation pre(underCharged) = SOC_start < 0; pre(overCharged) = SOC_start > 1; SOC = SOC_start; equation // Charge balance of battery PAct = if P > 0 then etaCha*P else (2-etaDis)*P; der(SOC)=PAct/EMax; // Equations to warn if state of charge exceeds 0 and 1 underCharged = SOC < 0; overCharged = SOC > 1; when change(underCharged) or change(overCharged) then assert(SOC >= 0, "Warning: Battery is below minimum charge.", level=AssertionLevel.warning); assert(SOC <= 1, "Warning: Battery is above maximum charge.", level=AssertionLevel.warning); end when; end Charge;