Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers
Economizer control of multi zone VAV AHU
Information
The package contains a multi zone VAV AHU economizer control sequence and the related economizer subsequences.
Package Content
| Name | Description |
|---|---|
 Controller
|
Multi zone VAV AHU economizer control sequence |
 Subsequences
|
Subsequences for economizer control |
 Validation
|
Collection of validation models |
Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers.Controller
Multi zone VAV AHU economizer control sequence
Information
Multi zone VAV AHU economizer control sequence that calculates outdoor and return air damper positions based on ASHRAE Guidline 36, PART5 sections: N.2.c, N.5, N.6.c, N.7, A.17, N.12.
The sequence consists of three subsequences.
-
First, the block
damLimcomputes the damper position limits to satisfy outdoor air requirements. See Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers.Subsequences.Limits for a description. -
Second, the block
enaDisenables or disables the economizer based on outdoor temperature and optionally enthalpy, and based on the supply fan status, freeze protection stage and zone state. See Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers.Subsequences.Enable for a description. -
Third, the block
modmodulates the outdoor and return damper position to track the supply air temperature setpoint, subject to the limits of the damper positions that were computed in the above two blocks. See Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers.Subsequences.Modulation for a description.
To enable freeze protection control logic that closes the outdoor air damper based
on the mixed air temperature TMix, set use_TMix=true.
This part of the control logic is not in Guideline 36, public review draft 1.
To enable the freeze protection according to Guideline 36, public review draft 1,
which may be revised in future versions, set
use_G36FrePro=true.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | use_enthalpy | false | Set to true if enthalpy measurement is used in addition to temperature measurement |
| Boolean | use_TMix | true | Set to true if mixed air temperature measurement is enabled |
| Boolean | use_G36FrePro | false | Set to true to use G36 freeze protection |
| Time | delta | 5 | Time horizon over which the outdoor air flow measurment is averaged [s] |
| Minimum outdoor air | |||
| SimpleController | controllerTypeMinOut | Buildings.Controls.OBC.CDL.T... | Type of controller |
| Real | kMinOut | 0.05 | Gain of controller for minimum outdoor air [1] |
| Time | TiMinOut | 1200 | Time constant of controller for minimum outdoor air intake [s] |
| Time | TdMinOut | 0.1 | Time constant of derivative block for minimum outdoor air intake [s] |
| Freeze protection | |||
| SimpleController | controllerTypeFre | Buildings.Controls.OBC.CDL.T... | Type of controller |
| Temperature | TFreSet | 279.15 | Lower limit for mixed air temperature for freeze protection, used if use_TMix=true [K] |
| Real | kFre | 0.1 | Gain for mixed air temperature tracking for freeze protection, used if use_TMix=true [1/K] |
| Time | TiFre | 120 | Time constant of controller for mixed air temperature tracking for freeze protection. Require TiFre < TiMinOut [s] |
| Economizer freeze protection | |||
| Time | TdFre | 0.1 | Time constant of derivative block for freeze protection [s] |
| Advanced | |||
| Hysteresis | |||
| TemperatureDifference | delTOutHis | 1 | Delta between the temperature hysteresis high and low limit [K] |
| SpecificEnergy | delEntHis | 1000 | Delta between the enthalpy hysteresis high and low limits [J/kg] |
| Delays at disable | |||
| Time | retDamFulOpeTim | 180 | Time period to keep RA damper fully open before releasing it for minimum outdoor airflow control at disable to avoid pressure fluctuations [s] |
| Time | disDel | 15 | Short time delay before closing the OA damper at disable to avoid pressure fluctuations [s] |
| Commissioning | |||
| Controller | |||
| Real | uHeaMax | -0.25 | Lower limit of controller input when outdoor damper opens for modulation control. Require -1 < uHeaMax < uCooMin < 1. |
| Real | uCooMin | +0.25 | Upper limit of controller input when return damper is closed for modulation control. Require -1 < uHeaMax < uCooMin < 1. |
| Real | uOutDamMax | (uHeaMax + uCooMin)/2 | Maximum loop signal for the OA damper to be fully open. Require -1 < uHeaMax < uOutDamMax <= uRetDamMin < uCooMin < 1. [1] |
| Real | uRetDamMin | (uHeaMax + uCooMin)/2 | Minimum loop signal for the RA damper to be fully open. Require -1 < uHeaMax < uOutDamMax <= uRetDamMin < uCooMin < 1. [1] |
| Physical damper position limits | |||
| Real | retDamPhyPosMax | 1 | Physically fixed maximum position of the return air damper [1] |
| Real | retDamPhyPosMin | 0 | Physically fixed minimum position of the return air damper [1] |
| Real | outDamPhyPosMax | 1 | Physically fixed maximum position of the outdoor air damper [1] |
| Real | outDamPhyPosMin | 0 | Physically fixed minimum position of the outdoor air damper [1] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | uTSup | Signal for supply air temperature control (T Sup Control Loop Signal in diagram) [1] |
| input RealInput | TOut | Outdoor air (OA) temperature [K] |
| input RealInput | TOutCut | OA temperature high limit cutoff. For differential dry bulb temeprature condition use return air temperature measurement [K] |
| input RealInput | hOut | Outdoor air enthalpy [J/kg] |
| input RealInput | hOutCut | OA enthalpy high limit cutoff. For differential enthalpy use return air enthalpy measurement [J/kg] |
| input RealInput | TMix | Measured mixed air temperature, used for freeze protection [K] |
| input RealInput | VOut_flow_normalized | Measured outdoor volumetric airflow rate, normalized by design minimum outdoor airflow rate [1] |
| input RealInput | VOutMinSet_flow_normalized | Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate [1] |
| input IntegerInput | uFreProSta | Freeze protection status |
| input IntegerInput | uOpeMod | AHU operation mode status signal |
| input BooleanInput | uSupFan | Supply fan status |
| output RealOutput | yRetDamPos | Return air damper position [1] |
| output RealOutput | yOutDamPos | Outdoor air damper position [1] |
Modelica definition
block Controller "Multi zone VAV AHU economizer control sequence"
parameter Boolean use_enthalpy=false
"Set to true if enthalpy measurement is used in addition to temperature measurement";
parameter Boolean use_TMix=true
"Set to true if mixed air temperature measurement is enabled";
parameter Boolean use_G36FrePro=false
"Set to true to use G36 freeze protection";
parameter Modelica.SIunits.TemperatureDifference delTOutHis=1
"Delta between the temperature hysteresis high and low limit";
parameter Modelica.SIunits.SpecificEnergy delEntHis=1000
"Delta between the enthalpy hysteresis high and low limits";
parameter Modelica.SIunits.Time retDamFulOpeTim=180
"Time period to keep RA damper fully open before releasing it for minimum outdoor airflow control at disable to avoid pressure fluctuations";
parameter Modelica.SIunits.Time disDel=15
"Short time delay before closing the OA damper at disable to avoid pressure fluctuations";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController controllerTypeMinOut=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI
"Type of controller";
parameter Real kMinOut(final unit="1")=0.05
"Gain of controller for minimum outdoor air";
parameter Modelica.SIunits.Time TiMinOut=1200
"Time constant of controller for minimum outdoor air intake";
parameter Modelica.SIunits.Time TdMinOut=0.1
"Time constant of derivative block for minimum outdoor air intake";
parameter Buildings.Controls.OBC.CDL.Types.SimpleController controllerTypeFre=
Buildings.Controls.OBC.CDL.Types.SimpleController.PI
"Type of controller";
parameter Modelica.SIunits.Temperature TFreSet = 279.15
"Lower limit for mixed air temperature for freeze protection, used if use_TMix=true";
parameter Real kFre(final unit="1/K") = 0.1
"Gain for mixed air temperature tracking for freeze protection, used if use_TMix=true";
parameter Modelica.SIunits.Time TiFre(max=TiMinOut)=120
"Time constant of controller for mixed air temperature tracking for freeze protection. Require TiFre < TiMinOut";
parameter Modelica.SIunits.Time TdFre=0.1
"Time constant of derivative block for freeze protection";
parameter Modelica.SIunits.Time delta=5
"Time horizon over which the outdoor air flow measurment is averaged";
parameter Real uHeaMax=-0.25
"Lower limit of controller input when outdoor damper opens for modulation control. Require -1 < uHeaMax < uCooMin < 1.";
parameter Real uCooMin=+0.25
"Upper limit of controller input when return damper is closed for modulation control. Require -1 < uHeaMax < uCooMin < 1.";
parameter Real uOutDamMax(
final min=-1,
final max=1,
final unit="1") = (uHeaMax + uCooMin)/2
"Maximum loop signal for the OA damper to be fully open. Require -1 < uHeaMax < uOutDamMax <= uRetDamMin < uCooMin < 1.";
parameter Real uRetDamMin(
final min=-1,
final max=1,
final unit="1") = (uHeaMax + uCooMin)/2
"Minimum loop signal for the RA damper to be fully open. Require -1 < uHeaMax < uOutDamMax <= uRetDamMin < uCooMin < 1.";
parameter Real retDamPhyPosMax(
final min=0,
final max=1,
final unit="1") = 1
"Physically fixed maximum position of the return air damper";
parameter Real retDamPhyPosMin(
final min=0,
final max=1,
final unit="1") = 0
"Physically fixed minimum position of the return air damper";
parameter Real outDamPhyPosMax(
final min=0,
final max=1,
final unit="1") = 1
"Physically fixed maximum position of the outdoor air damper";
parameter Real outDamPhyPosMin(
final min=0,
final max=1,
final unit="1") = 0
"Physically fixed minimum position of the outdoor air damper";
Buildings.Controls.OBC.CDL.Interfaces.RealInput uTSup(final unit="1")
"Signal for supply air temperature control (T Sup Control Loop Signal in diagram)";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TOut(
final unit="K",
final quantity="ThermodynamicTemperature") "Outdoor air (OA) temperature";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TOutCut(
final unit="K",
final quantity="ThermodynamicTemperature")
"OA temperature high limit cutoff. For differential dry bulb temeprature condition use return air temperature measurement";
Buildings.Controls.OBC.CDL.Interfaces.RealInput hOut(
final unit="J/kg",
final quantity="SpecificEnergy") if use_enthalpy "Outdoor air enthalpy";
Buildings.Controls.OBC.CDL.Interfaces.RealInput hOutCut(
final unit="J/kg",
final quantity="SpecificEnergy") if use_enthalpy
"OA enthalpy high limit cutoff. For differential enthalpy use return air enthalpy measurement";
Buildings.Controls.OBC.CDL.Interfaces.RealInput TMix(
final unit="K",
final quantity = "ThermodynamicTemperature") if use_TMix
"Measured mixed air temperature, used for freeze protection";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VOut_flow_normalized(
final unit="1")
"Measured outdoor volumetric airflow rate, normalized by design minimum outdoor airflow rate";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VOutMinSet_flow_normalized(
final unit="1")
"Effective minimum outdoor airflow setpoint, normalized by design minimum outdoor airflow rate";
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput uFreProSta if use_G36FrePro
"Freeze protection status";
Buildings.Controls.OBC.CDL.Interfaces.IntegerInput uOpeMod
"AHU operation mode status signal";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uSupFan
"Supply fan status";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yRetDamPos(
final min=0,
final max=1,
final unit="1") "Return air damper position";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yOutDamPos(
final min=0,
final max=1,
final unit="1") "Outdoor air damper position";
Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers.Subsequences.Enable
enaDis(
final use_enthalpy=use_enthalpy,
final delTOutHis=delTOutHis,
final delEntHis=delEntHis,
final retDamFulOpeTim=retDamFulOpeTim,
final disDel=disDel)
"Multi zone VAV AHU economizer enable/disable sequence";
Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers.Subsequences.Limits
damLim(
final retDamPhyPosMax=retDamPhyPosMax,
final retDamPhyPosMin=retDamPhyPosMin,
final outDamPhyPosMax=outDamPhyPosMax,
final outDamPhyPosMin=outDamPhyPosMin,
final k=kMinOut,
final Ti=TiMinOut,
final Td=TdMinOut,
final uRetDamMin=uRetDamMin,
final controllerType=controllerTypeMinOut)
"Multi zone VAV AHU economizer minimum outdoor air requirement damper limit sequence";
Buildings.Controls.OBC.ASHRAE.G36_PR1.AHUs.MultiZone.Economizers.Subsequences.Modulation
mod(
final uRetDamMin=uRetDamMin,
final uMin=uHeaMax,
final uMax=uCooMin,
final uOutDamMax=uOutDamMax)
"Multi zone VAV AHU economizer damper modulation sequence";
Buildings.Controls.OBC.ASHRAE.G36_PR1.Generic.FreezeProtectionMixedAir freProTMix(
final controllerType=controllerTypeFre,
final TFreSet = TFreSet,
final k=kFre,
final Ti=TiFre,
final Td=TdFre) if use_TMix
"Block that tracks TMix against a freeze protection setpoint";
protected
Buildings.Controls.OBC.CDL.Continuous.MovingMean movAve(final delta=delta)
"Moving average of outdoor air flow measurement, normalized by design minimum outdoor airflow rate";
Buildings.Controls.OBC.CDL.Continuous.Min outDamMaxFre
"Maximum control signal for outdoor air damper due to freeze protection";
Buildings.Controls.OBC.CDL.Continuous.Max retDamMinFre
"Minimum position for return air damper due to freeze protection";
Buildings.Controls.OBC.CDL.Continuous.Sources.Constant noTMix(k=0) if not use_TMix
"Ignore max evaluation if there is no mixed air temperature sensor";
Buildings.Controls.OBC.CDL.Continuous.Sources.Constant noTMix1(k=1) if not use_TMix
"Ignore min evaluation if there is no mixed air temperature sensor";
Buildings.Controls.OBC.CDL.Integers.Sources.Constant freProSta(
final k=Buildings.Controls.OBC.ASHRAE.G36_PR1.Types.FreezeProtectionStages.stage0) if not use_G36FrePro
"Freeze protection status is 0. Use if G36 freeze protection is not implemented";
equation
connect(uSupFan, enaDis.uSupFan);
connect(uFreProSta, enaDis.uFreProSta);
connect(hOutCut, enaDis.hOutCut);
connect(hOut, enaDis.hOut);
connect(TOutCut, enaDis.TOutCut);
connect(TOut, enaDis.TOut);
connect(VOutMinSet_flow_normalized, damLim.VOutMinSet_flow_normalized);
connect(uSupFan, damLim.uSupFan);
connect(uOpeMod, damLim.uOpeMod);
connect(uFreProSta, damLim.uFreProSta);
connect(damLim.yOutDamPosMax, enaDis.uOutDamPosMax);
connect(damLim.yOutDamPosMin, enaDis.uOutDamPosMin);
connect(damLim.yRetDamPosMin, enaDis.uRetDamPosMin);
connect(damLim.yRetDamPhyPosMax, enaDis.uRetDamPhyPosMax);
connect(damLim.yRetDamPosMax, enaDis.uRetDamPosMax);
connect(enaDis.yOutDamPosMax, mod.uOutDamPosMax);
connect(enaDis.yRetDamPosMax, mod.uRetDamPosMax);
connect(damLim.yOutDamPosMin, mod.uOutDamPosMin);
connect(enaDis.yRetDamPosMin, mod.uRetDamPosMin);
connect(uTSup, mod.uTSup);
connect(VOut_flow_normalized, movAve.u);
connect(movAve.y, damLim.VOut_flow_normalized);
connect(retDamMinFre.y, yRetDamPos);
connect(mod.yOutDamPos, outDamMaxFre.u1);
connect(outDamMaxFre.y, yOutDamPos);
connect(outDamMaxFre.u2, noTMix1.y);
connect(mod.yRetDamPos, retDamMinFre.u2);
connect(retDamMinFre.u1, noTMix.y);
connect(TMix, freProTMix.TMix);
connect(freProTMix.yFrePro, retDamMinFre.u1);
connect(freProTMix.yFreProInv, outDamMaxFre.u2);
connect(freProSta.y, damLim.uFreProSta);
connect(freProSta.y, enaDis.uFreProSta);
end Controller;