Buildings.DHC.Plants.Cooling.Controls
Package of control sequences for cooling plants
Information
This package contains control sequences for central cooling plants.
Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).
Package Content
| Name | Description |
|---|---|
 ChilledWaterBypass
|
Controller for chilled water bypass valve |
 ChilledWaterPumpSpeed
|
Controller for two headered variable speed chilled water pumps |
 ChillerStage
|
Chiller staging controller for plants with two chillers of the same size |
 FlowControl
|
This block controls the flow at the primary and secondary pumps |
 SelectMin
|
Block that includes or excludes storage plant pressure signal for min |
 TankStatus
|
Returns the tank status from its temperature sensors |
 Validation
|
Collection of validation models |
Buildings.DHC.Plants.Cooling.Controls.ChilledWaterBypass
Controller for chilled water bypass valve
Information
This model implements the chilled water loop bypass valve control logic as follows:
When the plant is on, the PID controller controls the valve opening ratio to reach the scaled mass flow rate setpoint.
The setpoint is mMin_flow multiplied by the number of chillers
that are on. mMin_flow is the minimum mass flow rate required by
one chiller.
This control sequence assumes that all the chillers are identical and the cooling load is evenly split between all of the chillers that are on.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | numChi | Number of chillers | |
| MassFlowRate | mMin_flow | Minimum mass flow rate of single chiller [kg/s] | |
| Real | k | 0.06 | Gain of controller |
| Time | Ti | 60 | Time constant of Integrator block [s] |
| SimpleController | controllerType | Modelica.Blocks.Types.Simple... | Type of controller |
Connectors
| Type | Name | Description |
|---|---|---|
| input BooleanInput | chiOn[numChi] | On signals of the chillers |
| input RealInput | mFloChi | Mass flow rate through the chillers [kg/s] |
| output RealOutput | y | Bypass valve opening ratio |
Modelica definition
model ChilledWaterBypass
"Controller for chilled water bypass valve"
extends Modelica.Blocks.Icons.Block;
parameter Integer numChi(
min=1)
"Number of chillers";
parameter Modelica.Units.SI.MassFlowRate mMin_flow
"Minimum mass flow rate of single chiller";
parameter Real k(min=0) = 0.06 "Gain of controller";
parameter Modelica.Units.SI.Time Ti(min=Modelica.Constants.small) = 60
"Time constant of Integrator block";
parameter Modelica.Blocks.Types.SimpleController controllerType=
Modelica.Blocks.Types.SimpleController.PI
"Type of controller";
Modelica.Blocks.Interfaces.BooleanInput chiOn[numChi]
"On signals of the chillers";
Modelica.Blocks.Interfaces.RealInput mFloChi(final unit="kg/s")
"Mass flow rate through the chillers";
Modelica.Blocks.Interfaces.RealOutput y
"Bypass valve opening ratio";
Buildings.Controls.OBC.CDL.Reals.PIDWithReset
bypValCon(
controllerType=controllerType,
final k=k,
final Ti=Ti,
y_reset=0)
"Chilled water bypass valve controller";
Modelica.Blocks.Math.BooleanToInteger booToInt[numChi]
"Boolean signal to integer";
Buildings.Controls.OBC.CDL.Integers.GreaterThreshold intGreThr
"Greater than zero";
Buildings.Controls.OBC.CDL.Integers.MultiSum numChiOn(nin=numChi)
"Number of chillers on";
Buildings.Controls.OBC.CDL.Conversions.IntegerToReal intToRea
"Integer to real";
Modelica.Blocks.Math.Gain mFloSetSca(k=1/numChi)
"Normalize mass flowrate setpoint";
Modelica.Blocks.Math.Gain mFloBypSca(k=1/(numChi*mMin_flow))
"Normalize the measured mass flowrate";
equation
connect(chiOn, booToInt.u);
connect(booToInt.y, numChiOn.u);
connect(numChiOn.y, intGreThr.u);
connect(intGreThr.y, bypValCon.trigger);
connect(numChiOn.y, intToRea.u);
connect(bypValCon.y, y);
connect(intToRea.y, mFloSetSca.u);
connect(mFloSetSca.y, bypValCon.u_s);
connect(mFloChi, mFloBypSca.u);
connect(mFloBypSca.y, bypValCon.u_m);
end ChilledWaterBypass;
Buildings.DHC.Plants.Cooling.Controls.ChilledWaterPumpSpeed
Controller for two headered variable speed chilled water pumps
Information
This model implements the control logic for variable speed pumps. The staging of pumps is implemented through an instance of Buildings.Applications.BaseClasses.Controls.VariableSpeedPumpStage.
The pump speed is controlled to maintain the pressure difference setpoint through a PI controller.
The model inputs are the measured chilled water mass flow rate
masFloPum and the pressure difference dpMea at a
reference point from the demand side. The output y is a vector
of pump speeds.
The model currently only supports the control of two variable speed pumps.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| PressureDifference | dpSetPoi | Pressure difference setpoint [Pa] | |
| Time | tWai | Waiting time [s] | |
| MassFlowRate | m_flow_nominal | Nominal mass flow rate of single chilled water pump [kg/s] | |
| Real | minSpe | 0.05 | Minimum speed ratio required by chilled water pumps [1] |
| MassFlowRate | criPoiFlo | 0.7*m_flow_nominal | Critcal point of flowrate for switching 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 |
| Speed Controller | |||
| SimpleController | controllerType | Modelica.Blocks.Types.Simple... | Type of pump speed controller |
| Real | k | 1 | Gain of controller [1] |
| Time | Ti | 60 | Time constant of Integrator block [s] |
| Time | Td | 0.1 | Time constant of Derivative block [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | masFloPum | Total mass flowrate of chilled water pumps [kg/s] |
| input RealInput | dpMea | Measured pressure difference [Pa] |
| output RealOutput | y[numPum] | Pump speed signal [1] |
| input BooleanInput | on | On signal of the plant |
Modelica definition
model ChilledWaterPumpSpeed
"Controller for two headered variable speed chilled water pumps"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.Units.SI.PressureDifference dpSetPoi(displayUnit="Pa")
"Pressure difference setpoint";
parameter Modelica.Units.SI.Time tWai "Waiting time";
parameter Modelica.Units.SI.MassFlowRate m_flow_nominal
"Nominal mass flow rate of single chilled water pump";
parameter Real minSpe(
final unit="1",
final min=0,
final max=1)=0.05
"Minimum speed ratio required by chilled water pumps";
parameter Modelica.Units.SI.MassFlowRate criPoiFlo=0.7*m_flow_nominal
"Critcal point of flowrate for switching pump on or off";
parameter Modelica.Units.SI.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";
parameter Modelica.Blocks.Types.SimpleController controllerType=
Modelica.Blocks.Types.SimpleController.PI
"Type of pump speed controller";
parameter Real k(
final unit="1",
final min=0)=1
"Gain of controller";
parameter Modelica.Units.SI.Time Ti(final min=Modelica.Constants.small) = 60
"Time constant of Integrator block";
parameter Modelica.Units.SI.Time Td(final min=0) = 0.1
"Time constant of Derivative block";
Modelica.Blocks.Interfaces.RealInput masFloPum(
final unit="kg/s")
"Total mass flowrate of chilled water pumps";
Modelica.Blocks.Interfaces.RealInput dpMea(
final unit="Pa")
"Measured pressure difference";
Modelica.Blocks.Interfaces.RealOutput y[numPum](
each final unit="1",
each final min=0,
each final max=1)
"Pump speed signal";
Modelica.Blocks.Math.Product pumSpe[numPum] "Output pump speed";
Buildings.Applications.BaseClasses.Controls.VariableSpeedPumpStage pumStaCon(
final tWai=tWai,
final m_flow_nominal=m_flow_nominal,
final minSpe=minSpe,
final criPoiFlo=criPoiFlo,
final deaBanFlo=deaBanFlo,
final criPoiSpe=criPoiSpe,
final deaBanSpe=deaBanSpe)
"Chilled water pump staging control";
Buildings.Controls.OBC.CDL.Reals.PIDWithReset conPID(
final controllerType=controllerType,
final Ti=Ti,
final k=k,
final Td=Td)
"PID controller of pump speed";
Modelica.Blocks.Sources.Constant dpSetSca(final k=1)
"Scaled differential pressure setpoint";
Modelica.Blocks.Math.Gain gai(k=1/dpSetPoi) "Gain for mesaured dp value";
Modelica.Blocks.Math.RealToBoolean twoPum(threshold=1.5) "Two pumps are on";
Modelica.Blocks.Math.Sum totPum(final nin=numPum) "Total number of pumps on";
Modelica.Blocks.Interfaces.BooleanInput on
"On signal of the plant";
Modelica.Blocks.Logical.Or orRes "Or block for controller reset";
protected
final parameter Integer numPum=2
"Number of chilled water pumps";
equation
connect(pumStaCon.masFloPum,masFloPum);
connect(conPID.y,pumStaCon.speSig);
connect(pumStaCon.y,pumSpe.u1);
connect(conPID.y,pumSpe[1].u2);
connect(conPID.y,pumSpe[2].u2);
connect(dpSetSca.y,conPID.u_s);
connect(dpMea, gai.u);
connect(gai.y, conPID.u_m);
connect(pumStaCon.y, totPum.u);
connect(totPum.y, twoPum.u);
connect(pumSpe.y, y);
connect(on, pumStaCon.on);
connect(twoPum.y, orRes.u2);
connect(on, orRes.u1);
connect(orRes.y, conPID.trigger);
end ChilledWaterPumpSpeed;
Buildings.DHC.Plants.Cooling.Controls.ChillerStage
Chiller staging controller for plants with two chillers of the same size
Information
This model implements the staging control logic as follows:
- When the plant enabling signal
onchanges fromfalsetotrue, one chiller is enabled. - When the total cooling load
QLoaexceeds 80 percent (adjustable) of one chiller's nominal capacityQChi_nominal, a second chiller is enabled. - When the total cooling load
QLoadrops below 60 percent (adjustable) of one chiller's nominal capacityQChi_nominal(i.e. 30 percent of both chillers combined), or the plant enabling signalonchanges fromtruetofalse, the second chiller is disabled. - When the plant enabling signal
onchanges fromtruetofalse, the operating chillers will be disabled sequentially. - Parameter
tWaiassures a transitional time is kept between each operation.
It is assumed that both chillers have the same capacity of
QChi_nominal.
Note: This model can be used for plants with two chillers with or without waterside econimizer (WSE). For plants with WSE, extra control logic on top of this model needs to be added.
.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| replaceable package Medium | Buildings.Media.Water | Service side medium | |
| Time | tWai | Waiting time [s] | |
| Power | QChi_nominal | Nominal cooling capacity (negative) [W] | |
| Power | staUpThr | -0.8*QChi_nominal | Stage up load threshold(from one to two chillers) [W] |
| Power | staDowThr | -0.6*QChi_nominal | Stage down load threshold(from two to one chiller) [W] |
Connectors
| Type | Name | Description |
|---|---|---|
| replaceable package Medium | Service side medium | |
| input BooleanInput | on | Enabling signal of the plant. True: chiller should be enabled |
| input RealInput | TChiWatRet | Chilled water return temperature |
| input RealInput | TChiWatSup | Chilled water supply temperature |
| input RealInput | mFloChiWat | Chilled water mass flow rate |
| output BooleanOutput | y[2] | On/off signal for the chillers - false: off; true: on |
Modelica definition
model ChillerStage
"Chiller staging controller for plants with two chillers of the same size"
replaceable package Medium=Buildings.Media.Water
constrainedby Modelica.Media.Interfaces.PartialMedium
"Service side medium";
parameter Modelica.Units.SI.Time tWai "Waiting time";
parameter Modelica.Units.SI.Power QChi_nominal(final max=0)
"Nominal cooling capacity (negative)";
parameter Modelica.Units.SI.Power staUpThr(final min=0) = -0.8*QChi_nominal
"Stage up load threshold(from one to two chillers)";
parameter Modelica.Units.SI.Power staDowThr(final min=0) = -0.6*QChi_nominal
"Stage down load threshold(from two to one chiller)";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot
"State graph root";
Modelica.Blocks.Interfaces.BooleanInput on
"Enabling signal of the plant. True: chiller should be enabled";
Modelica.Blocks.Interfaces.RealInput TChiWatRet
"Chilled water return temperature";
Modelica.Blocks.Interfaces.RealInput TChiWatSup
"Chilled water supply temperature";
Modelica.Blocks.Interfaces.RealInput mFloChiWat
"Chilled water mass flow rate";
Modelica.Blocks.Interfaces.BooleanOutput y[2]
"On/off signal for the chillers - false: off; true: on";
Modelica.StateGraph.InitialStep off(nIn=1, nOut=1)
"No cooling is demanded";
Modelica.StateGraph.StepWithSignal oneOn(
nOut=2,
nIn=2)
"Status of one chiller on";
Modelica.StateGraph.StepWithSignal twoOn(nOut=1, nIn=1)
"Status of two chillers on";
Modelica.StateGraph.TransitionWithSignal offToOne(
enableTimer=true,
waitTime=tWai)
"Condition of transition from off to one chiller on";
Modelica.StateGraph.TransitionWithSignal oneToTwo(
enableTimer=true,
waitTime=tWai)
"Condition of transition from one chiller to two chillers";
Modelica.StateGraph.TransitionWithSignal twoToOne(
enableTimer=true,
waitTime=tWai) "Condition of transion from two chillers to one chiller";
Modelica.StateGraph.TransitionWithSignal oneToOff(
enableTimer=true,
waitTime=tWai)
"Condition of transition from one chiller to off";
Buildings.Controls.OBC.CDL.Reals.Hysteresis thrOneToTwo(uLow=-staDowThr/
QChi_nominal, uHigh=-staUpThr/QChi_nominal)
"Threshold of turning two chillers on";
Modelica.Blocks.Logical.Not thrTwoToOne
"Threshold of turning off the second chiller";
Modelica.Blocks.Math.Add dT(
final k1=-1,
final k2=+1)
"Temperature difference";
Modelica.Blocks.Math.Product pro
"Product";
Modelica.Blocks.Math.Gain plr(final k=cp_default/QChi_nominal)
"Specific heat multiplier to calculate heat flow rate";
Buildings.Controls.OBC.CDL.Logical.Or Or "On signal for either chiller";
Modelica.Blocks.Logical.Not notOn "on switches to false";
Modelica.Blocks.Logical.Or TwoToOne
"Conditions that turn off the second chiller";
protected
final parameter Medium.ThermodynamicState sta_default=Medium.setState_pTX(
T=Medium.T_default,
p=Medium.p_default,
X=Medium.X_default)
"Medium state at default properties";
final parameter Modelica.Units.SI.SpecificHeatCapacity cp_default=
Medium.specificHeatCapacityCp(sta_default)
"Specific heat capacity of the fluid";
equation
connect(off.outPort[1],offToOne.inPort);
connect(oneToTwo.outPort,twoOn.inPort[1]);
connect(twoToOne.outPort,oneOn.inPort[2]);
connect(oneOn.outPort[2],oneToOff.inPort);
connect(oneOn.outPort[1],oneToTwo.inPort);
connect(oneToTwo.condition,thrOneToTwo.y);
connect(dT.y,pro.u1);
connect(plr.u, pro.y);
connect(plr.y, thrOneToTwo.u);
connect(dT.u1,TChiWatRet);
connect(TChiWatSup,dT.u2);
connect(pro.u2,mFloChiWat);
connect(oneToTwo.condition, thrTwoToOne.u);
connect(oneOn.active, Or.u1);
connect(twoOn.active, Or.u2);
connect(Or.y, y[1]);
connect(twoOn.active, y[2]);
connect(on, notOn.u);
connect(twoOn.outPort[1],twoToOne.inPort);
connect(offToOne.outPort,oneOn.inPort[1]);
connect(oneToOff.outPort,off.inPort[1]);
connect(on, offToOne.condition);
connect(thrTwoToOne.y, TwoToOne.u2);
connect(notOn.y, TwoToOne.u1);
connect(TwoToOne.y, twoToOne.condition);
connect(notOn.y, oneToOff.condition);
end ChillerStage;
Buildings.DHC.Plants.Cooling.Controls.FlowControl
This block controls the flow at the primary and secondary pumps
Information
This block implements a state graph to control the flows of the storage plant. It receives two tank status Boolean signals indicating that the tank is charged or empty. These two signals can be both false indicating an in-between state. The block can receive one of the following commands:
- Charge tank,
- No command, and
- Discharge tank.
The command to tank may be disregarded. For example, if the tank is receiving a discharge command but it is already empty, it will not discharge which would let warm return water directly into the supply side.
The system transitions among the following states:
| Step | Description | Transition in | Transition out |
|---|---|---|---|
| All Off (Initial Step) |
All off. This is the initial step. | - | - |
| Local Charging | Charge the tank with the local chiller. | "Charge tank" command AND tank is not charged yet AND chiller is enabled. This transition takes priority over the one below.1 |
The in-transition condition becomes false. |
| Remote Charging | Charge the tank with the remote chiller. | Same as above except that the chiller is not enabled. |
The in-transition condition becomes false. |
| Secondary Pump On | Turn on the secondary pump. This step is in parallel with the two below.2 |
The district has load AND the additional conditions of either step below become true. |
Both steps below are no longer active (implicit). |
| Tank Producing | The tank produces CHW to the district. This step is in parallel with "secondary pump on". |
The district has load AND "Discharge tank" command AND tank not empty. This transition takes priority over the one below. |
To "chiller producing": The in-transition condition becomes false AND The chiller is enabled. This transition takes priority over the one below. |
| To initial step: No load OR the in-transition conditions of "tank producing" and "chiller producing" are both false (i.e. neither tank or chiller is available). |
|||
| Chiller Producing | The chiller produces CHW to the district. This step is in parallel with "secondary pump on". |
The district has load AND the chiller is enabled. |
To "tank producing": The condition for in-transition of "tank producing" becomes true. This transition takes priority over the one below. |
| To initial step: No load OR the in-transition conditions of "tank producing" and "chiller producing" are both false. |
Notes:
- Out-transitions from the same step have priorities. When the conditions of more than one of them become true, the transition connected by a connector with the lowest index in the array fires. For example, even when the in-transition condition of "chiller producing" becomes true, as long as the in-transition condition of "tank producing" is also true, the latter fires because of priority.
- Steps that are in parallel are and must be active at the same time. When "secondary pump on" is active, either "tank producing" or "chiller producing" is also active.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Nominal values | |||
| MassFlowRate | mChi_flow_nominal | Nominal mass flow rate of the chiller loop [kg/s] | |
| MassFlowRate | mTan_flow_nominal | Nominal mass flow rate of the tank branch [kg/s] | |
| Dynamics | |||
| Filter | |||
| Boolean | use_outFil | true | = true, if output is filtered with a 2nd order CriticalDamping filter |
Connectors
| Type | Name | Description |
|---|---|---|
| input IntegerInput | com | Command: 1 = charge tank, 2 = no command, 3 = discharge tank |
| input BooleanInput | chiEnaSta | Chiller enable status, true if chiller is enabled |
| input BooleanInput | hasLoa | Set to true if there is a load |
| input RealInput | yPum | Normalized speed signal for the secondary pump [1] |
| output RealOutput | yVal | Valve normalized mass flow rate |
| output RealOutput | mPriPum_flow | Primary pump mass flow rate [kg/s] |
| output RealOutput | ySecPum | Secondary pump normalized speed [1] |
| input BooleanInput | tanSta[2] | Tank status - 1: is empty; 2: is charged; can be both false |
| output BooleanOutput | isChaRem | Is operated for remote charging |
Modelica definition
block FlowControl
"This block controls the flow at the primary and secondary pumps"
extends Modelica.Blocks.Icons.Block;
parameter Modelica.Units.SI.MassFlowRate mChi_flow_nominal
"Nominal mass flow rate of the chiller loop";
parameter Modelica.Units.SI.MassFlowRate mTan_flow_nominal
"Nominal mass flow rate of the tank branch";
parameter Boolean use_outFil=true
"= true, if output is filtered with a 2nd order CriticalDamping filter";
Modelica.Blocks.Interfaces.IntegerInput com
"Command: 1 = charge tank, 2 = no command, 3 = discharge tank";
Modelica.Blocks.Interfaces.BooleanInput chiEnaSta
"Chiller enable status, true if chiller is enabled";
Modelica.Blocks.Interfaces.BooleanInput hasLoa "Set to true if there is a load";
Modelica.Blocks.Interfaces.RealInput yPum(final unit="1")
"Normalized speed signal for the secondary pump";
Modelica.Blocks.Interfaces.RealOutput yVal "Valve normalized mass flow rate";
Modelica.Blocks.Interfaces.RealOutput mPriPum_flow(final unit="kg/s")
"Primary pump mass flow rate";
Modelica.Blocks.Interfaces.RealOutput ySecPum(final unit="1")
"Secondary pump normalized speed";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot "State graph root";
Modelica.StateGraph.InitialStep allOff(nOut=1, nIn=1) "Initial step, all off";
Modelica.StateGraph.Transition traChaLoc(condition=com == 1 and (not tanSta[2])
and chiEnaSta)
"Transition: Charge tank command AND tank not charged AND chiller enabled";
Modelica.StateGraph.Step steChaLoc(nIn=1, nOut=1) "Step: Local charging";
Modelica.StateGraph.Transition traRes1(condition=not traChaLoc.condition)
"Transition: Reset to initial step";
Modelica.StateGraph.Transition traChaRem(condition=com == 1 and (not tanSta[2])
and not chiEnaSta)
"Transition: Charge tank command AND tank not charged AND chiller not enabled";
Modelica.StateGraph.Step steChaRem(nIn=1, nOut=1) "Step: Remote charging";
Modelica.StateGraph.Transition traRes2(condition=not traChaRem.condition)
"Transition: Reset to initial step";
Modelica.StateGraph.Transition traProChi(condition=chiEnaSta)
"Transition: Chiller enabled";
Modelica.StateGraph.Step steProChi(nIn=2, nOut=2)
"Step: Chiller produces CHW";
Modelica.StateGraph.Transition traRes4(condition=not traPro.condition)
"Transition: Reset to initial step";
Modelica.StateGraph.Transition traProTan(condition=com == 3 and (not tanSta[1]))
"Transition: Tank commanded to discharge AND is not empty";
Modelica.StateGraph.Step steProTan(nIn=2, nOut=2) "Step: Tank produces CHW";
Modelica.StateGraph.Transition traRes3(condition=not traPro.condition)
"Transition: Reset to initial step";
Modelica.Blocks.Sources.BooleanExpression expPriPumFlo(
y=steChaLoc.active or steProChi.active)
"Expression for local charging OR chiller output";
Buildings.Controls.OBC.CDL.Conversions.BooleanToReal swiPriPum(realTrue=
mChi_flow_nominal, realFalse=0) "Switch for primary pump flow";
Modelica.Blocks.Sources.BooleanExpression expSecPum(y=stePumSecOn.active)
"Expression for tank output or chiller output";
Modelica.Blocks.Sources.BooleanExpression expVal(y=steChaRem.active)
"Boolean expression for remotely charging the tank";
Modelica.StateGraph.Alternative alt(nBranches=3)
"Alternative: Tank charging or plant outputting CHW";
Buildings.Controls.OBC.CDL.Reals.Switch swiSecPum
"Switch for secondary pump flow";
Modelica.Blocks.Sources.Constant zer(final k=0) "Constant zero";
Buildings.Controls.OBC.CDL.Conversions.BooleanToReal swiVal(realTrue=
mTan_flow_nominal, realFalse=0) "Switch for valve flow";
Modelica.Blocks.Interfaces.BooleanInput tanSta[2]
"Tank status - 1: is empty; 2: is charged; can be both false";
Modelica.StateGraph.Step stePumSecOn(nOut=1, nIn=1) "Step: Secondary pump on";
Modelica.StateGraph.Transition traPro(condition=hasLoa and (traProTan.condition
or traProChi.condition))
"Transition: Has load and the plant can produce CHW via either the chiller or the tank";
Modelica.StateGraph.Parallel parallel(nBranches=2)
"Parallel states of the components in the primary and secondary loops";
Modelica.StateGraph.Transition traTanToChi(condition=(not traProTan.condition)
and traProChi.condition)
"Transition: Tank no longer available (empty or commanded off) AND chiller available";
Modelica.StateGraph.Alternative altTanCha1(nBranches=2)
"Alternative: Tank charging locally or remotely";
Modelica.StateGraph.Step steRou1(nIn=1, nOut=1) "A step for routing only";
Modelica.StateGraph.Step steRou2(nIn=1, nOut=1) "A step for routing only";
Modelica.StateGraph.Transition traRou(final condition=true)
"A routing transition, always true";
Modelica.StateGraph.Transition traChiToTan(condition=traProTan.condition)
"Transition: Production priority handed to tank whenever possible";
Modelica.Blocks.Interfaces.BooleanOutput isChaRem
"Is operated for remote charging";
Modelica.Blocks.Sources.BooleanExpression booleanExpression(y=steChaRem.active);
equation
connect(traChaLoc.outPort,steChaLoc. inPort[1]);
connect(steChaLoc.outPort[1], traRes1.inPort);
connect(traChaRem.outPort,steChaRem. inPort[1]);
connect(steChaRem.outPort[1], traRes2.inPort);
connect(traProChi.outPort,steProChi. inPort[1]);
connect(traProTan.outPort,steProTan. inPort[1]);
connect(expPriPumFlo.y, swiPriPum.u);
connect(alt.inPort, allOff.outPort[1]);
connect(alt.outPort, allOff.inPort[1]);
connect(mPriPum_flow, swiPriPum.y);
connect(expSecPum.y, swiSecPum.u2);
connect(swiSecPum.u1, yPum);
connect(ySecPum, swiSecPum.y);
connect(zer.y, swiSecPum.u3);
connect(swiVal.u, expVal.y);
connect(swiVal.y, yVal);
connect(traPro.outPort, parallel.inPort);
connect(parallel.split[1], stePumSecOn.inPort[1]);
connect(stePumSecOn.outPort[1], parallel.join[1]);
connect(traTanToChi.outPort, steProChi.inPort[2]);
connect(traProTan.inPort, altTanCha1.split[1]);
connect(traRes3.outPort, altTanCha1.join[1]);
connect(traProChi.inPort, altTanCha1.split[2]);
connect(traRes4.outPort, altTanCha1.join[2]);
connect(steRou1.outPort[1], altTanCha1.inPort);
connect(altTanCha1.outPort,steRou2. inPort[1]);
connect(steRou1.inPort[1], parallel.split[2]);
connect(steRou2.outPort[1], parallel.join[2]);
connect(parallel.outPort, traRou.inPort);
connect(traChaLoc.inPort, alt.split[1]);
connect(traChaRem.inPort, alt.split[2]);
connect(traRes1.outPort, alt.join[1]);
connect(traRes2.outPort, alt.join[2]);
connect(traPro.inPort, alt.split[3]);
connect(traRou.outPort, alt.join[3]);
connect(booleanExpression.y, isChaRem);
connect(traChiToTan.outPort, steProTan.inPort[2]);
connect(steProChi.outPort[1], traChiToTan.inPort);
connect(steProChi.outPort[2], traRes4.inPort);
connect(steProTan.outPort[1], traTanToChi.inPort);
connect(steProTan.outPort[2], traRes3.inPort);
end FlowControl;
Buildings.DHC.Plants.Cooling.Controls.SelectMin
Block that includes or excludes storage plant pressure signal for min
Information
This block finds the minimum value from pressure head signals. The signal from the storage plant is included only when the plant is in remote charging mode.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | dpUse[nin] | Connector of Real input signals |
| input RealInput | dpStoPla | Connector of Real input signals |
| input BooleanInput | isChaRem | The storage plant is in remote charging mode |
| output RealOutput | y |
Modelica definition
block SelectMin
"Block that includes or excludes storage plant pressure signal for min"
extends Modelica.Blocks.Icons.Block;
parameter Integer nin
"Number of input connections";
Buildings.Controls.OBC.CDL.Interfaces.RealInput dpUse[nin]
"Connector of Real input signals";
Buildings.Controls.OBC.CDL.Interfaces.RealInput dpStoPla
"Connector of Real input signals";
Modelica.Blocks.Interfaces.BooleanInput isChaRem
"The storage plant is in remote charging mode";
Modelica.Blocks.Interfaces.RealOutput y;
equation
y = if isChaRem then
min(min(dpUse),dpStoPla)
else
min(dpUse);
end SelectMin;
Buildings.DHC.Plants.Cooling.Controls.TankStatus
Returns the tank status from its temperature sensors
Information
This model outputs tank status signals using the temperatures at the CHW tank top and the tank bottom as input. The status has two separate boolean signals indicating whether the tank is charged or empty (of cooling). The two output signals can be both false, indicating an in-between state, but they can never both be true.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Temperature | THig | Higher threshold to consider the tank empty [K] | |
| Temperature | TLow | Lower threshold to consider the tank full [K] | |
| TemperatureDifference | dTHys | 0.5 | Deadband for hysteresis [K] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | TTan[2] | Temperatures at the tank 1: top; and 2: bottom [K] |
| output BooleanOutput | y[2] | Tank status - y[1]=true is empty; y[2] = true is charged; both false means partially charged |
Modelica definition
block TankStatus "Returns the tank status from its temperature sensors"
parameter Modelica.Units.SI.Temperature THig
"Higher threshold to consider the tank empty";
parameter Modelica.Units.SI.Temperature TLow
"Lower threshold to consider the tank full";
parameter Modelica.Units.SI.TemperatureDifference dTHys(min=0.1) = 0.5
"Deadband for hysteresis";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TTan[2](
each final quantity="Temperature",
each final unit="K",
each displayUnit="degC") "Temperatures at the tank 1: top; and 2: bottom";
Buildings.Controls.OBC.CDL.Reals.Hysteresis hysCha(
final uLow=TLow,
final uHigh=TLow + dTHys) "Hysteresis, tank charged";
Buildings.Controls.OBC.CDL.Reals.Hysteresis hysEmp(
final uHigh=THig,
final uLow=THig - dTHys) "Hysteresis, tank empty";
Buildings.Controls.OBC.CDL.Logical.Not not1 "Not block";
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput y[2]
"Tank status - y[1]=true is empty; y[2] = true is charged; both false means partially charged";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant TTanTopChe(
final k(final unit="K", displayUnit="degC") = THig) "Set point for top temperatuer of tank";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant TTanBotChe(
final k(final unit="K", displayUnit="degC") = TLow) "Set point for bottom temperature of tank";
Buildings.Controls.OBC.CDL.Reals.Greater gre
"Test for temperature set points";
Buildings.Controls.OBC.CDL.Utilities.Assert assMes(
message = "THig must be greater than TLow.")
"Assertion if temperature set points are not correct";
equation
connect(hysCha.y, not1.u);
connect(TTan[1],hysCha. u);
connect(TTan[2],hysEmp. u);
connect(hysEmp.y, y[1]);
connect(not1.y, y[2]);
connect(TTanTopChe.y, gre.u1);
connect(TTanBotChe.y, gre.u2);
connect(gre.y, assMes.u);
end TankStatus;