Buildings.Applications.DataCenters.ChillerCooled.Controls
Package with control components for Buildings.Applications.DataCenters.ChillerCooled.Examples
Information
Collection of models for the control of chilled water system with waterside economizer.
Extends from Modelica.Icons.Package (Icon for standard packages).
Package Content
| Name | Description |
|---|---|
 ChillerStage
|
Chiller staging control logic |
 ConstantSpeedPumpStage
|
Staging control for constant speed pumps |
 CoolingMode
|
Mode controller for integrated waterside economizer and chiller |
 CoolingModeNonIntegrated
|
Cooling mode controller in the chilled water system with a non-integrated waterside economizer |
 CoolingTowerSpeed
|
Controller for the fan speed in cooling towers |
 Reheat
|
Model that implements an on and off controller for a reheater |
 VariableSpeedPumpStage
|
Staging control for variable speed pumps |
 Validation
|
Collection of validation models |
Buildings.Applications.DataCenters.ChillerCooled.Controls.ChillerStage
Chiller staging control logic
Information
This is a chiller staging control that works as follows:
- The chillers are all off when cooling mode is Free Cooling.
- One chiller is commanded on when cooling mode is not Free Cooling.
- Two chillers are commanded on when cooling mode is not Free Cooling and the cooling load addressed by each chiller is larger than a critical value.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | tWai | Waiting time [s] | |
| Power | QEva_nominal | Nominal cooling capaciaty(Negative means cooling) [W] | |
| Power | criPoiLoa | 0.55*QEva_nominal | Critical point of cooling load for switching one chiller on or off [W] |
| Power | dQ | 0.25*QEva_nominal | Deadband for critical point of cooling load [W] |
| Temperature | criPoiTem | 279.15 | Critical point of temperature for switching one chiller on or off [K] |
| TemperatureDifference | dT | 1 | Deadband width for critical point of switching temperature [K] |
Connectors
| Type | Name | Description |
|---|---|---|
| input IntegerInput | cooMod | Cooling mode signal, integer value of Buildings.Applications.DataCenters.Types.CoolingMode |
| input RealInput | QTot | Total cooling load in the chillers, negative |
| output RealOutput | y[2] | On/off signal for the chillers - 0: off; 1: on |
| input RealInput | TCHWSup | Temperature of leaving chilled water [K] |
Modelica definition
model ChillerStage "Chiller staging control logic"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.SIunits.Time tWai "Waiting time";
parameter Modelica.SIunits.Power QEva_nominal
"Nominal cooling capaciaty(Negative means cooling)";
parameter Modelica.SIunits.Power criPoiLoa = 0.55*QEva_nominal
"Critical point of cooling load for switching one chiller on or off";
parameter Modelica.SIunits.Power dQ = 0.25*QEva_nominal
"Deadband for critical point of cooling load";
parameter Modelica.SIunits.Temperature criPoiTem = 279.15
"Critical point of temperature for switching one chiller on or off";
parameter Modelica.SIunits.TemperatureDifference dT = 1
"Deadband width for critical point of switching temperature";
Modelica.Blocks.Interfaces.IntegerInput cooMod
"Cooling mode signal, integer value of
Buildings.Applications.DataCenters.Types.CoolingMode";
Modelica.Blocks.Interfaces.RealInput QTot
"Total cooling load in the chillers, negative";
Modelica.Blocks.Interfaces.RealOutput y[2]
"On/off signal for the chillers - 0: off; 1: on";
Modelica.Blocks.Interfaces.RealInput TCHWSup(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Temperature of leaving chilled water ";
Modelica.StateGraph.Transition con1(
enableTimer=true,
waitTime=tWai,
condition=cooMod > Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling))
"Fire condition 1: free cooling to partially mechanical cooling";
Modelica.StateGraph.StepWithSignal oneOn(nIn=2, nOut=2)
"One chiller is commanded on";
Modelica.StateGraph.InitialStep off(nIn=1) "Free cooling mode";
Modelica.StateGraph.StepWithSignal twoOn "Two chillers are commanded on";
Modelica.StateGraph.Transition con2(
enableTimer=true,
waitTime=tWai,
condition=cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FullMechanical) and
(-QTot > -(criPoiLoa + dQ) or TCHWSup > criPoiTem + dT))
"Fire condition 2: partially mechanical cooling to fully mechanical cooling";
Modelica.StateGraph.Transition con3(
enableTimer=true,
waitTime=tWai,
condition=(-QTot < -(criPoiLoa - dQ) or TCHWSup < criPoiTem - dT))
"Fire condition 3: fully mechanical cooling to partially mechanical cooling";
Modelica.StateGraph.Transition con4(
enableTimer=true,
waitTime=tWai,
condition=cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling))
"Fire condition 4: partially mechanical cooling to free cooling";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
Modelica.Blocks.Tables.CombiTable1Ds combiTable1Ds(
table=[0,0,0;
1,1,0;
2,1,1]);
Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger booToInt(
final integerTrue=1,
final integerFalse=0);
Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger booToInt1(
final integerFalse=0, final integerTrue=2);
Buildings.Controls.OBC.CDL.Integers.Add addInt;
Buildings.Controls.OBC.CDL.Conversions.IntegerToReal intToRea;
equation
connect(off.outPort[1], con1.inPort);
connect(con1.outPort, oneOn.inPort[1]);
connect(con2.inPort, oneOn.outPort[1]);
connect(con2.outPort, twoOn.inPort[1]);
connect(twoOn.outPort[1], con3.inPort);
connect(con4.outPort, off.inPort[1]);
connect(con3.outPort, oneOn.inPort[2]);
connect(con4.inPort, oneOn.outPort[2]);
connect(combiTable1Ds.y, y);
connect(twoOn.active, booToInt1.u);
connect(oneOn.active, booToInt.u);
connect(booToInt.y, addInt.u1);
connect(booToInt1.y, addInt.u2);
connect(addInt.y, intToRea.u);
connect(intToRea.y, combiTable1Ds.u);
end ChillerStage;
Buildings.Applications.DataCenters.ChillerCooled.Controls.ConstantSpeedPumpStage
Staging control for constant speed pumps
Information
This model describes a simple staging control for two constant-speed pumps in a chilled water plant with two chillers and a waterside economizer (WSE). The staging sequence is shown as below.
- When WSE is enabled, all the constant speed pumps are commanded on.
- When fully mechanical cooling (FMC) mode is enabled, the number of running constant speed pumps equals to the number of running chillers.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | tWai | Waiting time [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input IntegerInput | cooMod | Cooling mode - 0:off, 1: free cooling mode; 2: partially mechanical cooling; 3: fully mechanical cooling |
| input IntegerInput | numOnChi | The number of running chillers |
| output RealOutput | y[2] | On/off signal - 0: off; 1: on |
Modelica definition
model ConstantSpeedPumpStage "Staging control for constant speed pumps"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.SIunits.Time tWai "Waiting time";
Modelica.Blocks.Interfaces.IntegerInput cooMod
"Cooling mode - 0:off, 1: free cooling mode; 2: partially mechanical cooling; 3: fully mechanical cooling";
Modelica.Blocks.Interfaces.IntegerInput numOnChi
"The number of running chillers";
Modelica.Blocks.Interfaces.RealOutput y[2] "On/off signal - 0: off; 1: on";
Modelica.StateGraph.Transition con1(
enableTimer=true,
waitTime=tWai,
condition=
cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling)
or
cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.PartialMechanical)
or
cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FullMechanical))
"Fire condition 1: free cooling to partially mechanical cooling";
Modelica.StateGraph.StepWithSignal oneOn(nIn=2, nOut=2)
"One chiller is commanded on";
Modelica.StateGraph.InitialStep off(nIn=1) "Free cooling mode";
Modelica.StateGraph.StepWithSignal twoOn "Two chillers are commanded on";
Modelica.StateGraph.Transition con2(
enableTimer=true,
waitTime=tWai,
condition=
cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling)
or
cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.PartialMechanical)
or
(cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FullMechanical) and numOnChi > 1))
"Fire condition 2: partially mechanical cooling to fully mechanical cooling";
Modelica.StateGraph.Transition con3(
enableTimer=true,
waitTime=tWai,
condition=cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FullMechanical)
and numOnChi < 2)
"Fire condition 3: fully mechanical cooling to partially mechanical cooling";
Modelica.StateGraph.Transition con4(
enableTimer=true,
waitTime=tWai,
condition=cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling))
"Fire condition 4: partially mechanical cooling to free cooling";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
Modelica.Blocks.Tables.CombiTable1Ds combiTable1Ds(table=[0,0,0; 1,1,0; 2,1,1]);
Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger booToInt(
final integerTrue=1,
final integerFalse=0);
Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger booToInt1(
final integerFalse=0, final integerTrue=2);
Buildings.Controls.OBC.CDL.Integers.Add addInt;
Buildings.Controls.OBC.CDL.Conversions.IntegerToReal intToRea;
equation
connect(off.outPort[1], con1.inPort);
connect(con1.outPort, oneOn.inPort[1]);
connect(con2.inPort, oneOn.outPort[1]);
connect(con2.outPort, twoOn.inPort[1]);
connect(twoOn.outPort[1], con3.inPort);
connect(con4.outPort, off.inPort[1]);
connect(con3.outPort, oneOn.inPort[2]);
connect(con4.inPort, oneOn.outPort[2]);
connect(combiTable1Ds.y, y);
connect(oneOn.active, booToInt.u);
connect(twoOn.active, booToInt1.u);
connect(booToInt.y, addInt.u1);
connect(booToInt1.y, addInt.u2);
connect(intToRea.y, combiTable1Ds.u);
connect(addInt.y, intToRea.u);
end ConstantSpeedPumpStage;
Buildings.Applications.DataCenters.ChillerCooled.Controls.CoolingMode
Mode controller for integrated waterside economizer and chiller
Information
Controller that outputs if the chilled water system is in Free Cooling (FC) mode, Partially Mechanical Cooling (PMC) mode or Fully Mechanical Cooling (FMC) mode.
The waterside economizer is enabled when
- The waterside economizer has been disabled for at least 20 minutes, and
- TCHWR > TWetBul + TTowApp + deaBan1
The waterside economizer is disabled when
- The waterside economizer has been enabled for at least 20 minutes, and
- TWSE_CHWST > TWSE_CHWRT - deaBan2
The chiller is enabled when
- The chiller has been disabled for at leat 20 minutes, and
- TWSE_CHWST > TCHWSTSet + deaBan3
The chiller is disabled when
- The chiller has been enabled for at leat 20 minutes, and
- TWSE_CHWST ≤ TCHWSTSet + deaBan4
where TWSE_CHWST is the chilled water supply temperature for the WSE, TWetBul is the wet bulb temperature, TTowApp is the cooling tower approach, TWSE_CHWRT is the chilled water return temperature for the WSE, and TCHWSTSet is the chilled water supply temperature setpoint for the system. deaBan 1-4 are deadbands for each switching point.
References
- Stein, Jeff. Waterside Economizing in Data Centers: Design and Control Considerations. ASHRAE Transactions 115.2 (2009).
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | tWai | Waiting time [s] | |
| TemperatureDifference | deaBan1 | Dead band width 1 for switching chiller on [K] | |
| TemperatureDifference | deaBan2 | Dead band width 2 for switching waterside economizer off [K] | |
| TemperatureDifference | deaBan3 | Dead band width 3 for switching waterside economizer on [K] | |
| TemperatureDifference | deaBan4 | Dead band width 4 for switching chiller off [K] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | TCHWRetWSE | Temperature of entering chilled water that flows to waterside economizer [K] |
| input RealInput | TCHWSupWSE | Temperature of leaving chilled water that flows out from waterside economizer [K] |
| input RealInput | TCHWSupSet | Supply chilled water temperature setpoint [K] |
| input RealInput | TApp | Approach temperature in the cooling tower [K] |
| output IntegerOutput | y | Cooling mode signal, integer value of Buildings.Applications.DataCenters.Types.CoolingMode |
| input RealInput | TWetBul | Wet bulb temperature of outdoor air [K] |
Modelica definition
model CoolingMode
"Mode controller for integrated waterside economizer and chiller"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.SIunits.Time tWai "Waiting time";
parameter Modelica.SIunits.TemperatureDifference deaBan1
"Dead band width 1 for switching chiller on ";
parameter Modelica.SIunits.TemperatureDifference deaBan2
"Dead band width 2 for switching waterside economizer off";
parameter Modelica.SIunits.TemperatureDifference deaBan3
"Dead band width 3 for switching waterside economizer on ";
parameter Modelica.SIunits.TemperatureDifference deaBan4
"Dead band width 4 for switching chiller off";
Modelica.Blocks.Interfaces.RealInput TCHWRetWSE(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC")
"Temperature of entering chilled water that flows to waterside economizer ";
Modelica.Blocks.Interfaces.RealInput TCHWSupWSE(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC")
"Temperature of leaving chilled water that flows out from waterside economizer";
Modelica.Blocks.Interfaces.RealInput TCHWSupSet(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Supply chilled water temperature setpoint ";
Modelica.Blocks.Interfaces.RealInput TApp(
final quantity="TemperatureDifference",
final unit="K",
displayUnit="degC") "Approach temperature in the cooling tower";
Modelica.Blocks.Interfaces.IntegerOutput y
"Cooling mode signal, integer value of Buildings.Applications.DataCenters.Types.CoolingMode";
Modelica.StateGraph.Transition con1(
enableTimer=true,
waitTime=tWai,
condition=TCHWSupWSE > TCHWSupSet + deaBan1)
"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=TCHWRetWSE < TCHWSupWSE + deaBan2)
"Fire condition 2: partially mechanical cooling to fully mechanical cooling";
Modelica.StateGraph.Transition con3(
enableTimer=true,
waitTime=tWai,
condition=TCHWRetWSE > TWetBul + TApp + deaBan3)
"Fire condition 3: fully mechanical cooling to partially mechanical cooling";
Modelica.StateGraph.Transition con4(
enableTimer=true,
waitTime=tWai,
condition=TCHWSupWSE <= TCHWSupSet + deaBan4)
"Fire condition 4: partially mechanical cooling to free cooling";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
Modelica.Blocks.Interfaces.RealInput TWetBul(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC")
"Wet bulb temperature of outdoor air";
Modelica.Blocks.MathInteger.MultiSwitch swi(
y_default=0,
nu=3,
expr={Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling),
Integer(Buildings.Applications.DataCenters.Types.CoolingModes.PartialMechanical),
Integer(Buildings.Applications.DataCenters.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.y, y);
connect(freCoo.active, swi.u[1]);
connect(parMecCoo.active, swi.u[2]);
connect(fulMecCoo.active, swi.u[3]);
end CoolingMode;
Buildings.Applications.DataCenters.ChillerCooled.Controls.CoolingModeNonIntegrated
Cooling mode controller in the chilled water system with a non-integrated waterside economizer
Information
Chilled water plant with a non-integrated waterside economizer (WSE) have two cooling modes: free cooling (FC) mode and fully mechanical cooling (FMC) mode. This model determines when to activate FC or FMC for a chilled water system with 2 chillers and 1 waterside economizer.
The FMC mode is activated when
- TWetBulb≥ TWetBulb,tran, or
- TCHWST≥TCHWSTSet + deaBan,
and the FC mode is activated when
- TWetBulb< TWetBulb,tran, and
- numOnChi<2,
where TWetBulb is the wet bulb temperature of the outdoor air, TWetBulb,tran is the wet bulb temperature transition point for switching between FC and FMC, TCHWST is the chilled water supply temperature, TCHWSTSet is the chilled water supply temperature setpoint,and numOnChi is the number of running chillers.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| TemperatureDifference | deaBan | Dead band width for switching waterside economizer off [K] | |
| Temperature | TSwi | Temperature transition to free cooling mode [K] | |
| Time | tWai | Waiting time [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input IntegerInput | numOnChi | Number of running chillers |
| input RealInput | TWetBul | Wet bulb temperature of outdoor air [K] |
| input RealInput | TCHWSup | Temperature of leaving chilled water [K] |
| input RealInput | TCHWSupSet | Temperature setpoint of leaving chilled water [K] |
| output IntegerOutput | y | Cooling mode signal (1: free cooling mode, 3: fully mechanical cooling) |
Modelica definition
model CoolingModeNonIntegrated
"Cooling mode controller in the chilled water system with a non-integrated waterside economizer"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.SIunits.TemperatureDifference deaBan
"Dead band width for switching waterside economizer off ";
parameter Modelica.SIunits.Temperature TSwi
"Temperature transition to free cooling mode";
parameter Modelica.SIunits.Time tWai
"Waiting time";
Modelica.Blocks.Interfaces.IntegerInput numOnChi
"Number of running chillers";
Modelica.Blocks.Interfaces.RealInput TWetBul(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC")
"Wet bulb temperature of outdoor air";
Modelica.Blocks.Interfaces.RealInput TCHWSup(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Temperature of leaving chilled water ";
Modelica.Blocks.Interfaces.RealInput TCHWSupSet(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Temperature setpoint of leaving chilled water ";
Modelica.Blocks.Interfaces.IntegerOutput y
"Cooling mode signal (1: free cooling mode, 3: fully mechanical cooling)";
Modelica.StateGraph.InitialStepWithSignal freCoo(nIn=1)
"Free cooling mode";
Modelica.StateGraph.StepWithSignal fulMecCoo
"Fully mechanical cooling mode";
Modelica.StateGraph.Transition con1(
enableTimer=true,
waitTime=tWai,
condition=TWetBul > TSwi + deaBan or TCHWSup > TCHWSupSet + deaBan)
"Fire condition 1: free cooling to fully mechanical cooling";
Modelica.Blocks.MathInteger.MultiSwitch swi(
nu=2,
y_default=0,
expr={Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FreeCooling),
Integer(Buildings.Applications.DataCenters.Types.CoolingModes.FullMechanical)})
"Switch boolean signals to real signal";
Modelica.StateGraph.Transition con2(
enableTimer=true,
waitTime=tWai,
condition=TWetBul <= TSwi - deaBan and numOnChi == 1)
"Fire condition 2: fully mechanical cooling to free cooling";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
equation
connect(freCoo.outPort[1],con1. inPort);
connect(con1.outPort,fulMecCoo. inPort[1]);
connect(fulMecCoo.outPort[1], con2.inPort);
connect(con2.outPort, freCoo.inPort[1]);
connect(freCoo.active, swi.u[1]);
connect(fulMecCoo.active, swi.u[2]);
connect(swi.y, y);
end CoolingModeNonIntegrated;
Buildings.Applications.DataCenters.ChillerCooled.Controls.CoolingTowerSpeed
Controller for the fan speed in cooling towers
Information
This model describes a simple cooling tower speed controller for a chilled water system with integrated waterside economizers.
The control logics are described in the following:
- When the system is in Fully Mechanical Cooling (FMC) mode, the cooling tower fan speed is controlled to maintain the condener water supply temperature (CWST) at or around the setpoint.
- When the system is in Partially Mechanical Cooling (PMC) mode, the cooling tower fan speed is set as 100% to make condenser water as cold as possible and maximize the waterside economzier output.
- When the system is in Free Cooling (FC) mode, the cooling tower fan speed is controlled to maintain the chilled water supply temperature (CHWST) at or around its setpoint.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Controller | |||
| SimpleController | controllerType | Modelica.Blocks.Types.Simple... | Type of controller |
| Real | k | 1 | Gain of controller [1] |
| Time | Ti | 0.5 | Time constant of integrator block [s] |
| Time | Td | 0.1 | Time constant of derivative 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 RealInput | TCHWSupSet | Chilled water supply temperature setpoint [K] |
| input RealInput | TCWSupSet | Condenser water supply temperature setpoint [K] |
| input RealInput | TCHWSup | Chilled water supply temperature [K] |
| input RealInput | TCWSup | Condenser water supply temperature [K] |
| output RealOutput | y | Speed signal for cooling tower fans |
| input IntegerInput | cooMod | Cooling mode signal, integer value of Buildings.Applications.DataCenters.Types.CoolingMode |
Modelica definition
model CoolingTowerSpeed "Controller for the fan speed in cooling towers"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.Blocks.Types.SimpleController controllerType=
Modelica.Blocks.Types.SimpleController.PID
"Type of controller";
parameter Real k(min=0, unit="1") = 1
"Gain of controller";
parameter Modelica.SIunits.Time Ti(min=Modelica.Constants.small)=0.5
"Time constant of integrator block";
parameter Modelica.SIunits.Time Td(min=0)=0.1
"Time constant of derivative block";
parameter Real yMax(start=1)=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";
Modelica.Blocks.Interfaces.RealInput TCHWSupSet(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Chilled water supply temperature setpoint";
Modelica.Blocks.Interfaces.RealInput TCWSupSet(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Condenser water supply temperature setpoint";
Modelica.Blocks.Interfaces.RealInput TCHWSup(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Chilled water supply temperature ";
Modelica.Blocks.Interfaces.RealInput TCWSup(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="degC") "Condenser water supply temperature ";
Modelica.Blocks.Interfaces.RealOutput y
"Speed signal for cooling tower fans";
Modelica.Blocks.Sources.Constant uni(k=1) "Unit";
Modelica.Blocks.Sources.BooleanExpression pmcMod(
y= cooMod == Integer(Buildings.Applications.DataCenters.Types.CoolingModes.PartialMechanical))
"Partially mechanical cooling mode";
Modelica.Blocks.Interfaces.IntegerInput cooMod
"Cooling mode signal, integer value of
Buildings.Applications.DataCenters.Types.CoolingMode";
Buildings.Controls.Continuous.LimPID conPID(
controllerType=controllerType,
k=k,
Ti=Ti,
Td=Td,
yMax=yMax,
yMin=yMin,
reverseAction=reverseAction)
"PID controller";
Modelica.Blocks.Math.IntegerToBoolean fmcMod(threshold=3)
"Fully mechanical cooling mode";
protected
Modelica.Blocks.Logical.Switch swi1
"Switch 1";
Modelica.Blocks.Logical.Switch swi2
"Switch 2";
Modelica.Blocks.Logical.Switch swi3
"Switch 3";
equation
connect(TCWSupSet, swi1.u1);
connect(TCHWSupSet, swi1.u3);
connect(swi1.y, conPID.u_s);
connect(fmcMod.y, swi2.u2);
connect(TCWSup, swi2.u1);
connect(TCHWSup, swi2.u3);
connect(swi2.y, conPID.u_m);
connect(pmcMod.y, swi3.u2);
connect(uni.y, swi3.u1);
connect(conPID.y, swi3.u3);
connect(swi3.y, y);
connect(fmcMod.y, swi1.u2);
connect(cooMod, fmcMod.u);
end CoolingTowerSpeed;
Buildings.Applications.DataCenters.ChillerCooled.Controls.Reheat
Model that implements an on and off controller for a reheater
Information
This model can be used to generate on/off signal for the reheater inside the AHU.
This reheater will be on only if the following two conditions are satisfied at the same time:
- The position of the water-side valve reaches its switch point,
yValSwi; - The difference between the inlet temperature of the reheater and the required outlet temperature setpoint
is lower than its critical switch point,
dTSwi.
In addition, a deadband and waiting time is used to avoid frequent switching.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | yValSwi | yValSwi(min=0, max=1, unit="... | Switch point for valve signal [1] |
| Real | yValDeaBan | yValDeaBan(min=0, max=1, uni... | Deadband for valve signal [1] |
| TemperatureDifference | dTSwi | Switch point for temperature difference [K] | |
| TemperatureDifference | dTDeaBan | Deadband for temperature difference [K] | |
| Time | tWai | Waiting time [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | yVal | Valve position [1] |
| input RealInput | dT | Temperature difference [K] |
| output BooleanOutput | y | On and off signal for the reheater |
Modelica definition
model Reheat "Model that implements an on and off controller for a reheater"
parameter Real yValSwi(min=0, max=1, unit="1")
"Switch point for valve signal";
parameter Real yValDeaBan(min=0, max=1, unit="1")
"Deadband for valve signal";
parameter Modelica.SIunits.TemperatureDifference dTSwi
"Switch point for temperature difference";
parameter Modelica.SIunits.TemperatureDifference dTDeaBan
"Deadband for temperature difference";
parameter Modelica.SIunits.Time tWai
"Waiting time";
Modelica.Blocks.Interfaces.RealInput yVal(
min=0,
max=1,
unit="1") "Valve position";
Modelica.Blocks.Interfaces.RealInput dT(
final quantity="ThermodynamicTemperature",
final unit="K")
"Temperature difference";
Modelica.Blocks.Interfaces.BooleanOutput y
"On and off signal for the reheater";
Modelica.StateGraph.InitialStepWithSignal off "Off";
Modelica.StateGraph.StepWithSignal on "On";
Modelica.StateGraph.Transition offToOn(
enableTimer=true,
waitTime=tWai,
condition=yVal <= yValSwi - yValDeaBan and dT < dTSwi - dTDeaBan)
"Conditions that switch off to on";
Modelica.StateGraph.Transition onToOff(
condition=yVal > yValSwi+yValDeaBan or dT > dTSwi+dTDeaBan,
enableTimer=true,
waitTime=tWai)
"Conditions that switch on to off";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
equation
connect(off.outPort[1], offToOn.inPort);
connect(offToOn.outPort, on.inPort[1]);
connect(on.outPort[1], onToOff.inPort);
connect(onToOff.outPort, off.inPort[1]);
connect(on.active, y);
end Reheat;
Buildings.Applications.DataCenters.ChillerCooled.Controls.VariableSpeedPumpStage
Staging control for variable speed pumps
Information
This model implements a simple staging control logic for variable speed pumps.
- When the mass flowrate in each pump is greater than a threshold, and the speed signal is greater than a threshold, then activate one more pump;
- When the mass flowrate in each pump is less than a threshold, or the speed signal is smaller than a threshold, then deactivate one more pump.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | tWai | Waiting time [s] | |
| MassFlowRate | m_flow_nominal | Nominal mass flow rate of the identical variable-speed pumps [kg/s] | |
| Real | minSpe | 0.05 | Minimum speed ratio required by variable speed pumps [1] |
| MassFlowRate | criPoiFlo | 0.7*m_flow_nominal | Critcal point of flowrate for switch pump on or off [kg/s] |
| MassFlowRate | deaBanFlo | 0.1*m_flow_nominal | Deadband for critical point of flowrate [kg/s] |
| Real | criPoiSpe | 0.5 | Critical point of speed signal for switching on or off |
| Real | deaBanSpe | 0.3 | Deadband for critical point of speed signal |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | masFloPum | Total mass flowrate in the variable speed pumps |
| input RealInput | speSig | Speed signal |
| output RealOutput | y[2] | On/off signal - 0: off; 1: on |
Modelica definition
model VariableSpeedPumpStage "Staging control for variable speed pumps"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.SIunits.Time tWai "Waiting time";
parameter Modelica.SIunits.MassFlowRate m_flow_nominal
"Nominal mass flow rate of the identical variable-speed pumps";
parameter Real minSpe(unit="1",min=0,max=1) = 0.05
"Minimum speed ratio required by variable speed pumps";
parameter Modelica.SIunits.MassFlowRate criPoiFlo = 0.7*m_flow_nominal
"Critcal point of flowrate for switch pump on or off";
parameter Modelica.SIunits.MassFlowRate deaBanFlo = 0.1*m_flow_nominal
"Deadband for critical point of flowrate";
parameter Real criPoiSpe = 0.5
"Critical point of speed signal for switching on or off";
parameter Real deaBanSpe = 0.3
"Deadband for critical point of speed signal";
Modelica.Blocks.Interfaces.RealInput masFloPum
"Total mass flowrate in the variable speed pumps";
Modelica.Blocks.Interfaces.RealInput speSig
"Speed signal";
Modelica.Blocks.Interfaces.RealOutput y[2]
"On/off signal - 0: off; 1: on";
Modelica.StateGraph.Transition con1(
enableTimer=true,
waitTime=tWai,
condition=speSig > minSpe)
"Fire condition 1: free cooling to partially mechanical cooling";
Modelica.StateGraph.StepWithSignal oneOn(nIn=2, nOut=2)
"One chiller is commanded on";
Modelica.StateGraph.InitialStep off(nIn=1)
"Free cooling mode";
Modelica.StateGraph.StepWithSignal twoOn
"Two chillers are commanded on";
Modelica.StateGraph.Transition con2(
enableTimer=true,
waitTime=tWai,
condition=speSig > criPoiSpe + deaBanSpe and
masFloPum > criPoiFlo + deaBanFlo)
"Fire condition 2: partially mechanical cooling to fully mechanical cooling";
Modelica.StateGraph.Transition con3(
enableTimer=true,
waitTime=tWai,
condition=speSig < criPoiSpe - deaBanSpe
or masFloPum < criPoiFlo - deaBanFlo)
"Fire condition 3: fully mechanical cooling to partially mechanical cooling";
Modelica.StateGraph.Transition con4(
enableTimer=true,
waitTime=tWai,
condition=speSig <= minSpe)
"Fire condition 4: partially mechanical cooling to free cooling";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
Modelica.Blocks.Tables.CombiTable1Ds combiTable1Ds(
table=[0,0,0;
1,1,0;
2,1,1])
"Determine which pump should be on - rotation control is not considered here";
Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger booToInt(
final integerTrue=1,
final integerFalse=0);
Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger booToInt1(
final integerFalse=0, final integerTrue=2);
Buildings.Controls.OBC.CDL.Integers.Add addInt;
Buildings.Controls.OBC.CDL.Conversions.IntegerToReal intToRea;
equation
connect(off.outPort[1], con1.inPort);
connect(con1.outPort, oneOn.inPort[1]);
connect(con2.inPort, oneOn.outPort[1]);
connect(con2.outPort, twoOn.inPort[1]);
connect(twoOn.outPort[1], con3.inPort);
connect(con4.outPort, off.inPort[1]);
connect(con3.outPort, oneOn.inPort[2]);
connect(con4.inPort, oneOn.outPort[2]);
connect(combiTable1Ds.y, y);
connect(booToInt.u, oneOn.active);
connect(twoOn.active, booToInt1.u);
connect(booToInt.y, addInt.u1);
connect(booToInt1.y, addInt.u2);
connect(addInt.y, intToRea.u);
connect(intToRea.y, combiTable1Ds.u);
end VariableSpeedPumpStage;