Buildings.Applications.DataCenters.DXCooled.Controls
Package with controllers for DX-cooled data centers
Information
This package contains controllers for DX-cooled data centers.
Extends from Modelica.Icons.Package (Icon for standard packages).
Package Content
| Name | Description |
|---|---|
 AirsideEconomizer
|
Controller for airside economizer |
 Compressor
|
Controller for compressor speed |
 CoolingMode
|
Controller for the DX cooling system with an airside economizer |
 Validation
|
Collection of validation models |
Buildings.Applications.DataCenters.DXCooled.Controls.AirsideEconomizer
Controller for airside economizer
Information
This model implements an airside economizer controller to modulate the outdoor air damper in order to maintain desired mixed air temperature. When the airside economizer is open, which means the system is in free cooling or partial mechanical cooling, the position of the OA damper is controlled by a PI controller to maintain a desired mixed air temperature; otherwise, the position of the OA damper is set as closed.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | minOAFra | Minimum outdoor air fraction [1] | |
| Control | |||
| Real | gai | 1 | Gain of controller |
| Time | Ti | 50 | Integrator time [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | TMixAirSet | Mixed air setpoint temperature [K] |
| input RealInput | TMixAirMea | Measured mixed air temperature [K] |
| input IntegerInput | cooMod | Cooling mode of the cooling system |
| output RealOutput | y | Connector of Real output signal |
Modelica definition
model AirsideEconomizer "Controller for airside economizer"
parameter Real gai(min=Modelica.Constants.small) = 1 "Gain of controller";
parameter Modelica.SIunits.Time Ti=50 "Integrator time";
parameter Real minOAFra(
min=0,
max=1,
final unit="1") "Minimum outdoor air fraction";
Modelica.Blocks.Interfaces.RealInput TMixAirSet(
final unit="K",
final quantity="ThermodynamicTemperature",
displayUnit="degC") "Mixed air setpoint temperature";
Modelica.Blocks.Interfaces.RealInput TMixAirMea(
final unit="K",
final quantity="ThermodynamicTemperature",
displayUnit="degC") "Measured mixed air temperature";
Modelica.Blocks.Interfaces.IntegerInput cooMod
"Cooling mode of the cooling system";
Modelica.Blocks.Interfaces.RealOutput y "Connector of Real output signal";
Buildings.Controls.Continuous.LimPID con(
reverseAction=true,
k=gai,
yMin=minOAFra,
final controllerType=Modelica.Blocks.Types.SimpleController.PI,
Ti=Ti) "PID controller";
protected
Buildings.Controls.OBC.CDL.Continuous.Sources.Constant const(final k=0)
"Constant output signal with value 1";
Buildings.Controls.OBC.CDL.Integers.Sources.Constant conInt(final k=Integer(
Types.CoolingModes.FullMechanical))
"Outputs signal for full mechanical cooling";
Buildings.Controls.OBC.CDL.Integers.Equal ecoOff
"Determine if airside economizer is off";
Buildings.Controls.OBC.CDL.Logical.Switch switch1
"Switch to select control output";
equation
connect(TMixAirSet, con.u_s);
connect(TMixAirMea, con.u_m);
connect(switch1.y, y);
connect(ecoOff.y, switch1.u2);
connect(const.y, switch1.u1);
connect(con.y, switch1.u3);
connect(ecoOff.u2, conInt.y);
connect(ecoOff.u1, cooMod);
end AirsideEconomizer;
Buildings.Applications.DataCenters.DXCooled.Controls.Compressor
Controller for compressor speed
Information
This model implements a PI controller to maintain the supply air temperature at its setpoint by adjusting the compressor's speed. When the free cooling is activated, the DX unit is deactivated by setting the speed signal as 0. In Partial Mechanical cooling and Full Mechanical cooling, the PI controller works to adjust the compressor's speed.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | k | 0.5 | Gain of controller |
| Time | Ti | 240 | Time constant of integrator block [s] |
| Real | yMax | 1 | Upper limit of output |
| Real | yMin | 0 | Lower limit of output |
| Boolean | reverseAction | true | Set to true for throttling the water flow rate through a cooling coil controller |
Connectors
| Type | Name | Description |
|---|---|---|
| input IntegerInput | cooMod | Cooling mode of the cooling system |
| output RealOutput | y | Compressor speed [1] |
| input RealInput | TMixAirSet | Mixed air setpoint temperature [K] |
| input RealInput | TMixAirMea | Measured mixed air temperature [K] |
Modelica definition
model Compressor "Controller for compressor speed"
parameter Real k=0.5 "Gain of controller";
parameter Modelica.SIunits.Time Ti=240 "Time constant of integrator block";
parameter Real yMax=1 "Upper limit of output";
parameter Real yMin=0 "Lower limit of output";
parameter Boolean reverseAction=true
"Set to true for throttling the water flow rate through a cooling coil controller";
Buildings.Controls.Continuous.LimPID dxSpe(
Td=1,
final controllerType=Modelica.Blocks.Types.SimpleController.PI,
final k=k,
final Ti=Ti,
final yMax=yMax,
final yMin=yMin,
reverseAction=reverseAction,
reset=Buildings.Types.Reset.Parameter,
y_reset=yMin) "Controller for variable speed DX coil";
Modelica.Blocks.Interfaces.IntegerInput cooMod
"Cooling mode of the cooling system";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput y(
min=0,
max=1,
final unit="1") "Compressor speed";
Modelica.Blocks.Interfaces.RealInput TMixAirSet(
final unit="K",
final quantity="ThermodynamicTemperature",
displayUnit="degC") "Mixed air setpoint temperature";
Modelica.Blocks.Interfaces.RealInput TMixAirMea(
final unit="K",
final quantity="ThermodynamicTemperature",
displayUnit="degC") "Measured mixed air temperature";
Buildings.Controls.OBC.CDL.Logical.Not not1
"Negation of signal to trigger the integrator reset";
protected
Buildings.Controls.OBC.CDL.Integers.Sources.Constant conInt(final k=Integer(
Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling))
"Outputs signal for full mechanical cooling";
Buildings.Controls.OBC.CDL.Integers.Equal freCoo
"Determine if free cooling is on";
Buildings.Controls.OBC.CDL.Logical.Switch switch1
"Switch to select control output";
Buildings.Controls.OBC.CDL.Continuous.Sources.Constant const(final k=0)
"Constant output signal with value 1";
equation
connect(cooMod, freCoo.u1);
connect(conInt.y, freCoo.u2);
connect(freCoo.y, switch1.u2);
connect(const.y, switch1.u1);
connect(dxSpe.y, switch1.u3);
connect(switch1.y, y);
connect(TMixAirSet, dxSpe.u_s);
connect(TMixAirMea, dxSpe.u_m);
connect(not1.y, dxSpe.trigger);
connect(freCoo.y, not1.u);
end Compressor;
Buildings.Applications.DataCenters.DXCooled.Controls.CoolingMode
Controller for the DX cooling system with an airside economizer
Information
This model implements a cooling mode controller for an air-cooled direct expansion (DX) cooling system with an airside economizer. This controller is based on a simplified differential dry-bulb temperature control strategy, as described in ASHRAE G36.
There are three cooling modes for this system: free cooling (FC) mode, partially mechanical cooling (PMC) mode and fully mechanical cooling (FMC) mode. The detailed switching logic is shown in the following:
The airside economizer is enabled when:
- Tout<Tret
The airside economizer is disabled when:
- Tout>Tret
The DX coil is enabled when:
- Tout>Tsup,set
The DX coil is disabled when:
- Tout>Tsup,set
where Tswi is the switching temperature, subscript set means set point, out means outdoor air, ret means return air, and sup means supply air. A deadband δT can be added to the above logics to avoid frequent switching.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | tWai | Waiting time, set to avoid frequent switching [s] | |
| TemperatureDifference | dT | 1.1 | Deadband [K] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | TOutDryBul | Dry-bulb temperature of outdoor air [K] |
| input RealInput | TRet | Return air temperature [K] |
| input RealInput | TSupSet | Supply air temperature setpoint [K] |
| output IntegerOutput | y | Cooling mode signal, integer value of Buildings.Applications.DataCenters.Examples.BaseClasses.Types.CoolingMode |
Modelica definition
model CoolingMode
"Controller for the DX cooling system with an airside economizer"
parameter Modelica.SIunits.Time tWai
"Waiting time, set to avoid frequent switching";
parameter Modelica.SIunits.TemperatureDifference dT(min=0.1) = 1.1 "Deadband";
Modelica.Blocks.Interfaces.RealInput TOutDryBul(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Dry-bulb temperature of outdoor air";
Modelica.Blocks.Interfaces.RealInput TRet(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Return air temperature";
Modelica.Blocks.Interfaces.RealInput TSupSet(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Supply air temperature setpoint ";
Modelica.Blocks.Interfaces.IntegerOutput y
"Cooling mode signal, integer value of Buildings.Applications.DataCenters.Examples.BaseClasses.Types.CoolingMode";
Modelica.StateGraph.Transition con1(
enableTimer=true,
waitTime=tWai,
condition=TOutDryBul > TSupSet + dT)
"Fire condition 1: free cooling to partially mechanical cooling";
Modelica.StateGraph.StepWithSignal parMecCoo(nIn=2, nOut=2)
"Partial mechanical cooling mode";
Modelica.StateGraph.InitialStepWithSignal freCoo(nIn=1) "Free cooling mode";
Modelica.StateGraph.StepWithSignal fulMecCoo "Fully mechanical cooling mode";
Modelica.StateGraph.Transition con2(
enableTimer=true,
waitTime=tWai,
condition=TOutDryBul > TRet + dT)
"Fire condition 2: partially mechanical cooling to fully mechanical cooling";
Modelica.StateGraph.Transition con3(
enableTimer=true,
waitTime=tWai,
condition=TOutDryBul < TRet - dT)
"Fire condition 3: fully mechanical cooling to partially mechanical cooling";
Modelica.StateGraph.Transition con4(
enableTimer=true,
waitTime=tWai,
condition=TOutDryBul < TSupSet - dT)
"Fire condition 4: partially mechanical cooling to free cooling";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
Modelica.Blocks.MathInteger.MultiSwitch swi(
nu=3,
y_default=0,
expr={Integer(Types.CoolingModes.FreeCooling),Integer(Types.CoolingModes.PartialMechanical),
Integer(Types.CoolingModes.FullMechanical)})
"Switch boolean signals to real signal";
equation
connect(freCoo.outPort[1], con1.inPort);
connect(con1.outPort, parMecCoo.inPort[1]);
connect(con2.inPort, parMecCoo.outPort[1]);
connect(con2.outPort, fulMecCoo.inPort[1]);
connect(fulMecCoo.outPort[1], con3.inPort);
connect(con4.outPort, freCoo.inPort[1]);
connect(con3.outPort, parMecCoo.inPort[2]);
connect(con4.inPort, parMecCoo.outPort[2]);
connect(swi.u[1], freCoo.active);
connect(parMecCoo.active, swi.u[2]);
connect(fulMecCoo.active, swi.u[3]);
connect(y, swi.y);
end CoolingMode;