Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed
Package of sequences for cooling tower fan speed control
Information
This package contains sequences for cooling tower fan speed control. The implementation is based on section 5.20.12.2 in ASHRAE Guideline 36-2021.
Package Content
| Name | Description |
|---|---|
 Controller
|
Tower fan speed control |
 EnabledWSE
|
Package of sequences for control tower fan speed when waterside economizer is enabled |
| ReturnWaterTemperature
|
Sequences of control tower fan speed for controlling condenser water return temperature |
 Validation
|
Collection of validation models |
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.Controller
Tower fan speed control
Information
Block that outputs cooling tower fan speed ySpeSet. This is implemented
according to ASHRAE Guideline 36-2021, section 5.20.12.2, item a and c.
These sections specify sequences to control tower fan speed in the mode
when waterside economizer (if the plant does have it) is enabled or disabled, for
maintaining condenser water return temperature at its setpoint. This control is
used for plants with dynamic load profiles, i.e., those for which PLR may change
by more than approximately 25% in any hour.
It includes two subsequences:
- Sequence of controlling tower fan speed when waterside economizer is enabled, see Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.EnabledWSE.Controller for a description.
- Sequence of controlling the tower fan speed to maintain the condenser water return temperature at its setpoint. This control would be disabled if the waterside economizer is enabled. See Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Controller for a description.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | need_heaPreCon | true | True: the plant requires chiller head pressure being controlled |
| Integer | nChi | 2 | Total number of chillers |
| Integer | nTowCel | 4 | Total number of cooling tower cells |
| Integer | nConWatPum | 2 | Total number of condenser water pumps |
| TowerSpeedControl | fanSpeCon | Buildings.Controls.OBC.ASHRA... | Tower fan speed control type |
| Boolean | closeCoupledPlant | true | Flag to indicate if the plant is close coupled |
| Boolean | have_WSE | true | Flag to indicate if the plant has waterside economizer |
| Real | desCap | 1e6 | Plant design capacity [W] |
| Real | fanSpeMin | 0.1 | Minimum tower fan speed |
| WSE Enabled | |||
| Integrated | |||
| Real | chiMinCap[nChi] | {1e4,1e4} | Minimum cyclining load below which chiller will begin cycling [W] |
| SimpleController | intOpeCon | Buildings.Controls.OBC.CDL.T... | Type of controller |
| Real | kIntOpe | 1 | Gain of controller |
| Real | TiIntOpe | 0.5 | Time constant of integrator block [s] |
| Real | TdIntOpe | 0.1 | Time constant of derivative block [s] |
| WSE-only | |||
| SimpleController | chiWatCon | Buildings.Controls.OBC.CDL.T... | Type of controller |
| Real | kWSE | 1 | Gain of controller |
| Real | TiWSE | 0.5 | Time constant of integrator block [s] |
| Real | TdWSE | 0.1 | Time constant of derivative block [s] |
| Return temperature control | |||
| Setpoint | |||
| Real | minChiLif[nChi] | {12,12} | Minimum LIFT of each chiller [K] |
| Real | TConWatSup_nominal[nChi] | {293.15,293.15} | Design condenser water supply temperature (condenser entering) of each chiller [K] |
| Real | TConWatRet_nominal[nChi] | {303.15,303.15} | Design condenser water return temperature (condenser leaving) of each chiller [K] |
| Real | TChiWatSupMin[nChi] | {278.15,278.15} | Lowest chilled water supply temperature of each chiller [K] |
| Coupled plant | |||
| SimpleController | couPlaCon | Buildings.Controls.OBC.CDL.T... | Type of controller |
| Real | kCouPla | 1 | Gain of controller |
| Real | TiCouPla | 0.5 | Time constant of integrator block [s] |
| Real | TdCouPla | 0.1 | Time constant of derivative block [s] |
| Real | yCouPlaMax | 1 | Upper limit of output |
| Real | yCouPlaMin | 0 | Lower limit of output |
| Less coupled plant | |||
| Real | samplePeriod | 30 | Period of sampling condenser water supply and return temperature difference |
| SimpleController | supWatCon | Buildings.Controls.OBC.CDL.T... | Type of controller |
| Real | kSupCon | 1 | Gain of controller |
| Real | TiSupCon | 0.5 | Time constant of integrator block [s] |
| Real | TdSupCon | 0.1 | Time constant of derivative block [s] |
| Real | ySupConMax | 1 | Upper limit of output |
| Real | ySupConMin | 0 | Lower limit of output |
| Advanced | |||
| Real | speChe | 0.005 | Lower threshold value to check fan or pump speed |
| Return temperature control: Enable tower | |||
| Real | cheMinFanSpe | 300 | Threshold time for checking duration when tower fan equals to the minimum tower fan speed [s] |
| Real | cheMaxTowSpe | 300 | Threshold time for checking duration when any enabled chiller maximum cooling speed equals to the minimum tower fan speed [s] |
| Real | cheTowOff | 60 | Threshold time for checking duration when there is no enabled tower fan [s] |
| Return temperature control: Setpoint | |||
| Real | iniPlaTim | 600 | Time to hold return temperature to initial setpoint after plant being enabled [s] |
| Real | ramTim | 180 | Time to ramp return water temperature from initial value to setpoint [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | uChiLoa | Current cooling load [W] |
| input BooleanInput | uChi[nChi] | Chiller enabling status: true=ON |
| input BooleanInput | uWse | Waterside economizer enabling status: true=ON |
| input RealInput | TChiWatSup | Chilled water supply temperature [K] |
| input RealInput | TChiWatSupSet | Chilled water supply temperature setpoint [K] |
| input RealInput | reqPlaCap | Current required plant capacity [W] |
| input RealInput | uMaxSpeSet[nChi] | Maximum cooling tower speed setpoint from each chiller head pressure control loop [1] |
| input BooleanInput | uTow[nTowCel] | Cooling tower cell operating status: true=running tower cell |
| input BooleanInput | uPla | Plant enabling status |
| input RealInput | TConWatRet | Condenser water return temperature (condenser leaving) [K] |
| input BooleanInput | uConWatPum[nConWatPum] | Current condenser water pump status |
| input RealInput | TConWatSup | Condenser water supply temperature (condenser entering) [K] |
| output RealOutput | ySpeSet | Fan speed setpoint of each cooling tower cell [1] |
| output RealOutput | yLifMax | Maximum LIFT among enabled chillers [K] |
| output RealOutput | yLifMin | Minimum LIFT among enabled chillers [K] |
| output RealOutput | TConWatRetSet | Condenser water return temperature setpoint [K] |
| output RealOutput | TConWatSupSet | Condenser water supply temperature setpoint [K] |
Modelica definition
block Controller "Tower fan speed control"
parameter Boolean need_heaPreCon = true
"True: the plant requires chiller head pressure being controlled";
parameter Integer nChi=2 "Total number of chillers";
parameter Integer nTowCel=4 "Total number of cooling tower cells";
parameter Integer nConWatPum=2 "Total number of condenser water pumps";
parameter Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Types.TowerSpeedControl
fanSpeCon=
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Types.TowerSpeedControl.CondenserWaterReturnTemperaure
"Tower fan speed control type";
final parameter Boolean have_conWatRetCon = fanSpeCon==Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Types.TowerSpeedControl.CondenserWaterReturnTemperaure
"True: the fan speed is controlled to maintain the condenser water return temperature setpoint";
parameter Boolean closeCoupledPlant=true
"Flag to indicate if the plant is close coupled";
parameter Boolean have_WSE=true
"Flag to indicate if the plant has waterside economizer";
parameter Real desCap(unit="W")=1e6 "Plant design capacity";
parameter Real fanSpeMin=0.1 "Minimum tower fan speed";
parameter Real chiMinCap[nChi](
final unit=fill("W", nChi))={1e4,1e4}
"Minimum cyclining load below which chiller will begin cycling";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController intOpeCon=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI
"Type of controller";
parameter Real kIntOpe=1 "Gain of controller";
parameter Real TiIntOpe(unit="s")=0.5
"Time constant of integrator block";
parameter Real TdIntOpe(unit="s")=0.1
"Time constant of derivative block";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController chiWatCon=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI
"Type of controller";
parameter Real kWSE=1 "Gain of controller";
parameter Real TiWSE(unit="s")=0.5
"Time constant of integrator block";
parameter Real TdWSE(unit="s")=0.1
"Time constant of derivative block";
parameter Real minChiLif[nChi](unit=fill("K", nChi))={12,12} "Minimum LIFT of each chiller";
parameter Real TConWatSup_nominal[nChi](
unit=fill("K", nChi),
each displayUnit="degC")={293.15,293.15}
"Design condenser water supply temperature (condenser entering) of each chiller";
parameter Real TConWatRet_nominal[nChi](
unit=fill("K", nChi),
each displayUnit="degC")={303.15,303.15}
"Design condenser water return temperature (condenser leaving) of each chiller";
parameter Real TChiWatSupMin[nChi](
unit=fill("K", nChi),
each displayUnit="degC")={278.15,278.15}
"Lowest chilled water supply temperature of each chiller";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController couPlaCon=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI "Type of controller";
parameter Real kCouPla=1 "Gain of controller";
parameter Real TiCouPla(unit="s")=0.5
"Time constant of integrator block";
parameter Real TdCouPla(unit="s")=0.1
"Time constant of derivative block";
parameter Real yCouPlaMax=1 "Upper limit of output";
parameter Real yCouPlaMin=0 "Lower limit of output";
parameter Real samplePeriod=30
"Period of sampling condenser water supply and return temperature difference";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController supWatCon=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI "Type of controller";
parameter Real kSupCon=1 "Gain of controller";
parameter Real TiSupCon(unit="s")=0.5
"Time constant of integrator block";
parameter Real TdSupCon(unit="s")=0.1
"Time constant of derivative block";
parameter Real ySupConMax=1 "Upper limit of output";
parameter Real ySupConMin=0 "Lower limit of output";
parameter Real speChe=0.005 "Lower threshold value to check fan or pump speed";
parameter Real cheMinFanSpe(unit="s")=300
"Threshold time for checking duration when tower fan equals to the minimum tower fan speed";
parameter Real cheMaxTowSpe(unit="s")=300
"Threshold time for checking duration when any enabled chiller maximum cooling speed equals to the minimum tower fan speed";
parameter Real cheTowOff(unit="s")=60
"Threshold time for checking duration when there is no enabled tower fan";
parameter Real iniPlaTim(unit="s")=600
"Time to hold return temperature to initial setpoint after plant being enabled";
parameter Real ramTim(unit="s")=180
"Time to ramp return water temperature from initial value to setpoint";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uChiLoa(final unit="W",
final quantity="HeatFlowRate") if have_WSE "Current cooling load";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uChi[nChi]
"Chiller enabling status: true=ON";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uWse if have_WSE
"Waterside economizer enabling status: true=ON";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TChiWatSup(
final unit="K",
displayUnit="degC",
final quantity="ThermodynamicTemperature") if have_WSE
"Chilled water supply temperature";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TChiWatSupSet(
final unit="K",
displayUnit="degC",
final quantity="ThermodynamicTemperature")
"Chilled water supply temperature setpoint";
Buildings.Controls.OBC.CDL.Interfaces.RealInput reqPlaCap(
final unit="W",
final quantity="HeatFlowRate") "Current required plant capacity";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uMaxSpeSet[nChi](
final min=fill(0, nChi),
final max=fill(1, nChi),
final unit=fill("1", nChi)) if need_heaPreCon
"Maximum cooling tower speed setpoint from each chiller head pressure control loop";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uTow[nTowCel]
"Cooling tower cell operating status: true=running tower cell";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uPla
"Plant enabling status";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TConWatRet(
final unit="K",
displayUnit="degC",
final quantity="ThermodynamicTemperature") if have_conWatRetCon
"Condenser water return temperature (condenser leaving)";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uConWatPum[nConWatPum]
"Current condenser water pump status";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TConWatSup(
final unit="K",
displayUnit="degC",
final quantity="ThermodynamicTemperature")
if have_conWatRetCon and not closeCoupledPlant
"Condenser water supply temperature (condenser entering)";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput ySpeSet(
final min=0,
final max=1,
final unit="1") if have_conWatRetCon
"Fan speed setpoint of each cooling tower cell";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yLifMax(
final unit="K") if have_conWatRetCon
"Maximum LIFT among enabled chillers";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yLifMin(
final unit="K") if have_conWatRetCon
"Minimum LIFT among enabled chillers";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput TConWatRetSet(
final quantity="ThermodynamicTemperature",
displayUnit="degC",
final unit="K") if have_conWatRetCon
"Condenser water return temperature setpoint";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput TConWatSupSet(
final quantity="ThermodynamicTemperature",
displayUnit="degC",
final unit="K") if have_conWatRetCon and not closeCoupledPlant
"Condenser water supply temperature setpoint";
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.ReturnWaterTemperature.Controller
fanSpeRetTem(
final need_heaPreCon=need_heaPreCon,
final nChi=nChi,
final nTowCel=nTowCel,
final nConWatPum=nConWatPum,
final have_WSE=have_WSE,
final closeCoupledPlant=closeCoupledPlant,
final desCap=desCap,
final fanSpeMin=fanSpeMin,
final minChiLif=minChiLif,
final TConWatRet_nominal=TConWatRet_nominal,
final TConWatSup_nominal=TConWatSup_nominal,
final TChiWatSupMin=TChiWatSupMin,
final cheMinFanSpe=cheMinFanSpe,
final cheMaxTowSpe=cheMaxTowSpe,
final cheTowOff=cheTowOff,
final iniPlaTim=iniPlaTim,
final ramTim=ramTim,
final couPlaCon=couPlaCon,
final kCouPla=kCouPla,
final TiCouPla=TiCouPla,
final yCouPlaMax=yCouPlaMax,
final yCouPlaMin=yCouPlaMin,
final TdCouPla=TdCouPla,
final supWatCon=supWatCon,
final kSupCon=kSupCon,
final TiSupCon=TiSupCon,
final TdSupCon=TdSupCon,
final ySupConMax=ySupConMax,
final ySupConMin=ySupConMin,
final speChe=speChe) if have_conWatRetCon
"Fan speed control based on condenser water return temperature control";
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Towers.FanSpeed.EnabledWSE.Controller
fanSpeWse(
final nChi=nChi,
final chiMinCap=chiMinCap,
final fanSpeMin=fanSpeMin,
final intOpeCon=intOpeCon,
final kIntOpe=kIntOpe,
final TiIntOpe=TiIntOpe,
final TdIntOpe=TdIntOpe,
final fanSpeChe=speChe,
final chiWatCon=chiWatCon,
final kWSE=kWSE,
final TiWSE=TiWSE,
final TdWSE=TdWSE) if have_WSE
"Tower fan speed when waterside economizer is enabled";
Buildings.Controls.OBC.CDL.Logical.Sources.Constant con1(
final k=fanSpeCon == Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Types.TowerSpeedControl.CondenserWaterReturnTemperaure)
"Check if the speed control is for returning water temperature";
Buildings.Controls.OBC.CDL.Utilities.Assert assMes(
final message="The tower speed control should be for controlling the return temperature setpoint.")
"Tower speed control warning";
equation
connect(fanSpeWse.ySpeSet, fanSpeRetTem.uSpeWSE);
connect(fanSpeWse.uChiLoa, uChiLoa);
connect(fanSpeWse.uChi, uChi);
connect(fanSpeWse.uWse, uWse);
connect(fanSpeWse.TChiWatSup, TChiWatSup);
connect(fanSpeWse.TChiWatSupSet, TChiWatSupSet);
connect(uChi, fanSpeRetTem.uChi);
connect(uWse, fanSpeRetTem.uWse);
connect(fanSpeRetTem.reqPlaCap, reqPlaCap);
connect(fanSpeRetTem.uMaxSpeSet, uMaxSpeSet);
connect(fanSpeRetTem.uTow, uTow);
connect(TChiWatSupSet, fanSpeRetTem.TChiWatSupSet);
connect(fanSpeRetTem.uPla, uPla);
connect(fanSpeRetTem.TConWatRet, TConWatRet);
connect(fanSpeRetTem.TConWatSup, TConWatSup);
connect(fanSpeRetTem.ySpeSet,ySpeSet);
connect(fanSpeRetTem.yLifMax, yLifMax);
connect(fanSpeRetTem.yLifMin, yLifMin);
connect(fanSpeRetTem.TConWatRetSet, TConWatRetSet);
connect(fanSpeRetTem.TConWatSupSet, TConWatSupSet);
connect(uConWatPum, fanSpeRetTem.uConWatPum);
connect(con1.y, assMes.u);
end Controller;