Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls

Package of control blocks for fifth generation DHC ETS

Information

This package contains control blocks for energy transfer stations in fifth generation district heating and cooling systems.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name	Description
Borefield	Borefield controller
Chiller	Chiller controller
HeatExchanger	District heat exchanger controller
PIDWithEnable	PID controller with enable signal
PredictLeavingTemperature	Block that predicts heat exchanger leaving water temperature
PrimaryVariableFlow	Ideal control of condenser or evaporator variable flow rate
Reset	Supervisory supply temperature reset
SideCold	Control block for cold side
SideHot	Control block for hot side
Supervisory	Supervisory controller
SwitchBox	Controller for flow switch box
WatersideEconomizer	Waterside economizer controller
BaseClasses	Package with base classes

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Borefield

Borefield controller

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Borefield

Information

This block implements the control logic for the borefield system. The main control signal u is yielded by the hot side or cold side controller, see for instance Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideHot.

The system is enabled when

the main control signal is greater than zero,
the return position of at least one isolation valve is greater than 90%.

When the system is enabled,

the input signal is mapped to modulate in sequence the mixing valve (from full bypass to closed bypass for a control signal varying between 0% and 30%) and the pump speed (from the minimum to the maximum value for a control signal varying between 30% and 100%),
a PI loop tracks the maximum inlet temperature, the minimum between this loop output and the previously mapped signal being used to modulate the valve.

Note that the first control signal for the valve is needed to stabilize the control of the system when the mass flow rate required to meet the heat or cold rejection demand is below the flow rate corresponding to the minimum pump speed.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Temperature	TBorWatEntMax		Maximum value of borefield water entering temperature [K]
Real	spePumBorMin	0.1	Borefield pump minimum speed [1]

Connectors

Type	Name	Description
input RealInput	yValIso_actual[2]	Isolation valves return position (fractional)
input RealInput	u	Control signal from supervisory
output RealOutput	yPum	Control signal for borefield pump [kg/s]
output RealOutput	yValMix	Control signal for borefield mixing valve [1]
input RealInput	TBorWatEnt	Borefield water entering temperature [K]

Modelica definition

model Borefield "Borefield controller" extends Modelica.Blocks.Icons.Block; parameter Modelica.Units.SI.Temperature TBorWatEntMax(displayUnit="degC") "Maximum value of borefield water entering temperature"; parameter Real spePumBorMin( final unit="1")=0.1 "Borefield pump minimum speed"; Buildings.Controls.OBC.CDL.Interfaces.RealInput yValIso_actual[2] "Isolation valves return position (fractional)"; Buildings.Controls.OBC.CDL.Interfaces.RealInput u "Control signal from supervisory"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yPum( final unit="kg/s") "Control signal for borefield pump"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yValMix( final unit="1") "Control signal for borefield mixing valve"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TBorWatEnt( final unit="K", displayUnit="degC") "Borefield water entering temperature"; Buildings.Controls.OBC.CDL.Continuous.PIDWithReset conMix( final yMin=0, final yMax=1, final reverseActing=true, y_reset=0, k=0.1, final controllerType=Modelica.Blocks.Types.SimpleController.PI, Ti( displayUnit="s")=120) "Mixing valve controller"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant maxTBorWatEnt( y(final unit="K", displayUnit="degC"), final k=TBorWatEntMax) "Maximum value of borefield water entering temperature"; Buildings.Controls.OBC.CDL.Continuous.GreaterThreshold opeVal( final t=0.9, final h=0.1) "True if at least one isolation valve is open"; Buildings.Controls.OBC.CDL.Continuous.MultiMax multiMax1( final nin=2) "Maximum opening"; Buildings.Controls.OBC.CDL.Continuous.GreaterThreshold enaSup( final t=0.05, final h=0.025) "Borefield enabled from supervisory"; Buildings.Controls.OBC.CDL.Continuous.Switch runBor "Enable borefield system pump"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant limVal( final k=0.3) "Control signal value for full opening of the valve"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant speMin( final k=spePumBorMin) "Minimum pump speed"; Buildings.Controls.OBC.CDL.Logical.And enaBor "Borefield enable signal"; Buildings.Controls.OBC.CDL.Continuous.Line mapSpe "Mapping function for pump speed"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant one( final k=1) "One"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant zer( final k=0) "Zero"; Buildings.Controls.OBC.CDL.Continuous.Line mapVal "Mapping function for valve opening"; Buildings.Controls.OBC.CDL.Continuous.Min min1 "Minimum"; equation connect(multiMax1.y,opeVal.u); connect(yValIso_actual,multiMax1.u); connect(u,enaSup.u); connect(enaSup.y,enaBor.u1); connect(opeVal.y,enaBor.u2); connect(enaBor.y,conMix.trigger); connect(maxTBorWatEnt.y,conMix.u_s); connect(runBor.y,yPum); connect(TBorWatEnt,conMix.u_m); connect(enaBor.y,runBor.u2); connect(mapSpe.y,runBor.u1); connect(u,mapSpe.u); connect(speMin.y,mapSpe.f1); connect(min1.y,yValMix); connect(conMix.y,min1.u2); connect(mapVal.y,min1.u1); connect(one.y,mapSpe.x2); connect(one.y,mapSpe.f2); connect(one.y,mapVal.f2); connect(zer.y,mapVal.x1); connect(limVal.y,mapVal.x2); connect(u,mapVal.u); connect(limVal.y,mapSpe.x1); connect(zer.y,mapVal.f1); connect(zer.y,runBor.u3); end Borefield;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Chiller

Chiller controller

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Chiller

Information

This is a controller for the chiller system, which includes the dedicated condenser and evaporator pumps.

The system is enabled if any of the input control signals uHea or uCoo is true. When enabled,

the condenser and evaporator pumps are operated at constant speed,
the condenser (resp. evaporator) mixing valve is modulated with a PI loop controlling the minimum (resp. maximum) inlet temperature.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Temperature	TConWatEntMin		Minimum value of condenser water entering temperature [K]
Temperature	TEvaWatEntMax		Maximum value of evaporator water entering temperature [K]

Connectors

Type	Name	Description
input BooleanInput	uCoo	Cooling enable signal
input BooleanInput	uHea	Heating enable signal
input RealInput	TConWatEnt	Condenser water entering temperature [K]
input RealInput	TEvaWatEnt	Evaporator water entering temperature [K]
output RealOutput	yValCon	Condenser mixing valve control signal
output RealOutput	yValEva	Evaporator mixing valve control signal
output BooleanOutput	yChi	Chiller enable signal

Modelica definition

model Chiller "Chiller controller" extends Modelica.Blocks.Icons.Block; parameter Modelica.Units.SI.Temperature TConWatEntMin(displayUnit="degC") "Minimum value of condenser water entering temperature"; parameter Modelica.Units.SI.Temperature TEvaWatEntMax(displayUnit="degC") "Maximum value of evaporator water entering temperature"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uCoo "Cooling enable signal"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uHea "Heating enable signal"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TConWatEnt( final unit="K", displayUnit="degC") "Condenser water entering temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TEvaWatEnt( final unit="K", displayUnit="degC") "Evaporator water entering temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yValCon "Condenser mixing valve control signal"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yValEva "Evaporator mixing valve control signal"; Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput yChi "Chiller enable signal"; Buildings.Controls.OBC.CDL.Logical.Or heaOrCoo "Heating or cooling enabled"; PIDWithEnable conValEva( final controllerType=Modelica.Blocks.Types.SimpleController.PI, final yMax=1, final yMin=0, y_reset=0, k=0.1, Ti( displayUnit="s")=60, final reverseActing=true) "Evaporator three-way valve control"; PIDWithEnable conValCon( final controllerType=Modelica.Blocks.Types.SimpleController.PI, final yMax=1, final yMin=0, y_reset=0, k=0.1, Ti( displayUnit="s")=60, final reverseActing=false) "Condenser three-way valve control"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant maxTEvaWatEnt( y(final unit="K", displayUnit="degC"), final k=TEvaWatEntMax) "Maximum value of evaporator water entering temperature"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant minTConWatEnt( y(final unit="K", displayUnit="degC"), final k=TConWatEntMin) "Minimum value of condenser water entering temperature"; equation connect(TEvaWatEnt,conValEva.u_m); connect(TConWatEnt,conValCon.u_m); connect(heaOrCoo.y,yChi); connect(uHea,heaOrCoo.u1); connect(uCoo,heaOrCoo.u2); connect(maxTEvaWatEnt.y,conValEva.u_s); connect(minTConWatEnt.y,conValCon.u_s); connect(conValEva.y,yValEva); connect(heaOrCoo.y,conValEva.uEna); connect(heaOrCoo.y,conValCon.uEna); connect(conValCon.y,yValCon); end Chiller;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.HeatExchanger

District heat exchanger controller

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.HeatExchanger

Information

This block implements the control logic for the district heat exchanger, which realizes the interface between the building system and the district system.

The input signal u is yielded by the supervisory controller, see Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Supervisory. The primary and secondary circuits are enabled to operate if this input signal is greater than zero and the return position of at least one isolation valve is greater than 90%. When enabled,

the secondary circuit is controlled based on the input signal u, which is mapped to modulate in sequence the mixing valve (from full bypass to closed bypass for a control signal varying between 0% and 30%) and the pump speed (from the minimum to the maximum value for a control signal varying between 30% and 100%),
the primary pump speed (or valve opening) is directly modulated with the input signal u.

Note that the valve on the secondary side is needed to stabilize the control of the system when the secondary mass flow rate required to meet the heat or cold rejection demand is below the flow rate corresponding to the minimum pump speed.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
ConnectionConfiguration	conCon		District connection configuration
Real	spePum1Min	0.1	Heat exchanger primary pump minimum speed (fractional) [1]
Real	spePum2Min	0.1	Heat exchanger secondary pump minimum speed (fractional) [1]

Connectors

Type	Name	Description
input RealInput	yValIso[2]	Isolation valves return position (index 1 for condenser)
output RealOutput	y1	District heat exchanger primary control signal [1]
output RealOutput	yPum2	District heat exchanger secondary pump control signal [1]
output RealOutput	yVal2	District heat exchanger secondary valve control signal [1]
input RealInput	u	Control signal for secondary side (from supervisory)

Modelica definition

model HeatExchanger "District heat exchanger controller" extends Modelica.Blocks.Icons.Block; parameter DHC.EnergyTransferStations.Types.ConnectionConfiguration conCon "District connection configuration"; parameter Real spePum1Min( final unit="1", min=0)=0.1 "Heat exchanger primary pump minimum speed (fractional)"; parameter Real spePum2Min( final unit="1", min=0.01)=0.1 "Heat exchanger secondary pump minimum speed (fractional)"; Buildings.Controls.OBC.CDL.Interfaces.RealInput yValIso[2] "Isolation valves return position (index 1 for condenser)"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput y1(final unit="1") "District heat exchanger primary control signal"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yPum2( final unit="1") "District heat exchanger secondary pump control signal"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yVal2( final unit="1") "District heat exchanger secondary valve control signal"; Buildings.Controls.OBC.CDL.Continuous.Max max1 "Maximum between control signal and minimum speed or opening"; Buildings.Controls.OBC.CDL.Continuous.Switch swiOff1 "Output zero if not enabled"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant min1( final k=if have_val1 then 0 else spePum1Min) "Minimum pump speed or actuator opening"; Buildings.Controls.OBC.CDL.Interfaces.RealInput u "Control signal for secondary side (from supervisory)"; Buildings.Controls.OBC.CDL.Continuous.GreaterThreshold greThr( final t=0.01, final h=0.005) "Check for heat or cold rejection demand"; Buildings.Controls.OBC.CDL.Logical.And and2 "At least one valve is open and HX circuit is enabled"; Buildings.Controls.OBC.CDL.Continuous.GreaterThreshold heaRej( final t=0.9, final h=0.1) "Heat rejection if condenser isolation valve is open"; Buildings.Controls.OBC.CDL.Continuous.GreaterThreshold cooRej( final t=0.9, final h=0.1) "Cold rejection if evaporator isolation valve is open"; Buildings.Controls.OBC.CDL.Logical.Or or1 "At least one valve is open "; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant speMin( final k=spePum2Min) "Minimum pump speed"; Buildings.Controls.OBC.CDL.Continuous.Switch swiOff2 "Output zero if not enabled"; Buildings.Controls.OBC.CDL.Continuous.Line mapSpe "Mapping function for pump speed"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant one( final k=1) "One"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant zer( final k=0) "Zero"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant hal( final k=0.3) "Control signal value for full opening of the valve"; Buildings.Controls.OBC.CDL.Continuous.Line mapVal "Mapping function for valve opening"; protected parameter Boolean have_val1=conCon == DHC.EnergyTransferStations.Types.ConnectionConfiguration.TwoWayValve "True in case of control valve on district side, false in case of a pump"; equation connect(swiOff1.y, y1); connect(max1.y,swiOff1.u1); connect(u,greThr.u); connect(greThr.y,and2.u1); connect(and2.y,swiOff1.u2); connect(cooRej.y,or1.u2); connect(heaRej.y,or1.u1); connect(or1.y,and2.u2); connect(min1.y,max1.u2); connect(swiOff2.y,yPum2); connect(one.y,mapSpe.x2); connect(one.y,mapSpe.f2); connect(u,mapSpe.u); connect(speMin.y,mapSpe.f1); connect(mapSpe.y,swiOff2.u1); connect(zer.y,swiOff2.u3); connect(zer.y,swiOff1.u3); connect(hal.y,mapSpe.x1); connect(u,mapVal.u); connect(zer.y,mapVal.x1); connect(zer.y,mapVal.f1); connect(one.y,mapVal.f2); connect(hal.y,mapVal.x2); connect(mapVal.y,yVal2); connect(and2.y,swiOff2.u2); connect(u, max1.u1); connect(yValIso[1], heaRej.u); connect(yValIso[2], cooRej.u); end HeatExchanger;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.PIDWithEnable

PID controller with enable signal

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.PIDWithEnable

Information

This is an update of Buildings.Controls.OBC.CDL.Continuous.PIDWithReset with an additional Boolean input representing an enable signal.

When enabled, the controller output is identical to Buildings.Controls.OBC.CDL.Continuous.PIDWithReset (and the controller integral term is reset to yMin at enabling time).
When disabled, the controller output is zero (and the set point is replaced by the measurement signal to avoid any time integration of the control error).

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
SimpleController	controllerType	Buildings.Controls.OBC.CDL.T...	Type of controller
Real	k	1	Gain of controller
Time	Ti	0.5	Time constant of integrator block [s]
Time	Td	0.1	Time constant of derivative block [s]
Real	r	1	Typical range of control error, used for scaling the control error
Real	yMin	0	Lower limit of output
Real	yMax	1	Upper limit of output
Boolean	reverseActing	true	Set to true for reverse acting, or false for direct acting control action
Real	y_reset	yMin	Value to which the controller output is reset if the boolean trigger has a rising edge

Connectors

Type	Name	Description
input RealInput	u_s	Connector of setpoint input signal
input RealInput	u_m	Connector of measurement input signal
output RealOutput	y	Connector of actuator output signal
input BooleanInput	uEna	Enable signal

Modelica definition

block PIDWithEnable "PID controller with enable signal" extends Modelica.Blocks.Icons.Block; parameter Buildings.Controls.OBC.CDL.Types.SimpleController controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI "Type of controller"; parameter Real k( min=0)=1 "Gain of controller"; parameter Modelica.Units.SI.Time Ti(min=Buildings.Controls.OBC.CDL.Constants.small)= 0.5 "Time constant of integrator block"; parameter Modelica.Units.SI.Time Td(min=0) = 0.1 "Time constant of derivative block"; parameter Real r( min=100*Modelica.Constants.eps)=1 "Typical range of control error, used for scaling the control error"; parameter Real yMin=0 "Lower limit of output"; parameter Real yMax=1 "Upper limit of output"; parameter Boolean reverseActing=true "Set to true for reverse acting, or false for direct acting control action"; parameter Real y_reset=yMin "Value to which the controller output is reset if the boolean trigger has a rising edge"; Buildings.Controls.OBC.CDL.Interfaces.RealInput u_s "Connector of setpoint input signal"; Buildings.Controls.OBC.CDL.Interfaces.RealInput u_m "Connector of measurement input signal"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput y "Connector of actuator output signal"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uEna "Enable signal"; Buildings.Controls.OBC.CDL.Continuous.PIDWithReset conPID( final k=k, final Ti=Ti, final Td=Td, final r=r, final controllerType=controllerType, final yMin=yMin, final yMax=yMax, final reverseActing=reverseActing, final y_reset=y_reset); Buildings.Controls.OBC.CDL.Continuous.Switch swi; Buildings.Controls.OBC.CDL.Continuous.Switch swi1; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant valDis( final k=0) "Value when disabled"; equation connect(conPID.u_s,swi.y); connect(uEna,swi.u2); connect(u_s,swi.u1); connect(u_m,swi.u3); connect(uEna,conPID.trigger); connect(u_m,conPID.u_m); connect(conPID.y,swi1.u1); connect(swi1.y,y); connect(uEna,swi1.u2); connect(valDis.y,swi1.u3); end PIDWithEnable;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.PredictLeavingTemperature

Block that predicts heat exchanger leaving water temperature

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.PredictLeavingTemperature

Information

This block computes the predicted heat exchanger leaving water temperature as used in Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.WatersideEconomizer.

The predicted heat exchanger approach is computed as

dTApp = dTApp_nominal * m2_flow / m2_flow_nominal.

Which gives the predicted heat exchanger leaving water temperature as

T2WatLvg = T1WatEnt + dTApp.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Description
Nominal condition
TemperatureDifference	dTApp_nominal	Heat exchanger approach [K]
MassFlowRate	m2_flow_nominal	Heat exchanger secondary mass flow rate [kg/s]

Connectors

Type	Name	Description
input RealInput	T1WatEnt	Heat exchanger primary water entering temperature [K]
output RealOutput	T2WatLvg	Heat exchanger secondary water leaving temperature [K]
input RealInput	m2_flow	Heat exchanger secondary mass flow rate [kg/s]

Modelica definition

model PredictLeavingTemperature "Block that predicts heat exchanger leaving water temperature" extends Modelica.Blocks.Icons.Block; parameter Modelica.Units.SI.TemperatureDifference dTApp_nominal "Heat exchanger approach"; parameter Modelica.Units.SI.MassFlowRate m2_flow_nominal "Heat exchanger secondary mass flow rate"; Buildings.Controls.OBC.CDL.Interfaces.RealInput T1WatEnt( final unit="K", displayUnit="degC") "Heat exchanger primary water entering temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput T2WatLvg( final unit="K", displayUnit="degC") "Heat exchanger secondary water leaving temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput m2_flow( final unit="kg/s") "Heat exchanger secondary mass flow rate"; protected Real ratLoa "Part load ratio"; equation ratLoa = min(1, abs(m2_flow / m2_flow_nominal)); T2WatLvg = T1WatEnt + dTApp_nominal * ratLoa; end PredictLeavingTemperature;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.PrimaryVariableFlow

Ideal control of condenser or evaporator variable flow rate

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.PrimaryVariableFlow

Information

This block implements an ideal control of the evaporator (or condenser) water mass flow rate. The control intent aims to maintain a constant water temperature difference dT_nominal across the heat exchanger, within the limit of a minimum mass flow rate ratio ratFloMin. For computational performance and to avoid the use of a PI controller, the required mass flow rate is computed based on a signal representative of the load.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
HeatFlowRate	Q_flow_nominal		Heat flow rate at nominal conditions (>0 for condenser) [W]
TemperatureDifference	dT_nominal		DeltaT at nominal conditions (>0 for condenser) [K]
Real	ratFloMin	0.3	Minimum mass flow rate (ratio to nominal) [1]

Connectors

Type	Name	Description
input RealInput	loa	Signal approximating the load on condenser or evaporator [W]
output RealOutput	m_flow	Mass flow rate [kg/s]

Modelica definition

block PrimaryVariableFlow "Ideal control of condenser or evaporator variable flow rate" extends Modelica.Blocks.Icons.Block; parameter Modelica.Units.SI.HeatFlowRate Q_flow_nominal "Heat flow rate at nominal conditions (>0 for condenser)"; parameter Modelica.Units.SI.TemperatureDifference dT_nominal(min=if Q_flow_nominal > 0 then Modelica.Constants.eps else -100, max=if Q_flow_nominal < 0 then -Modelica.Constants.eps else 100) "DeltaT at nominal conditions (>0 for condenser)"; parameter Real ratFloMin( final unit="1", final min=0, final max=1)=0.3 "Minimum mass flow rate (ratio to nominal)"; constant Modelica.Units.SI.SpecificHeatCapacity cp=Buildings.Utilities.Psychrometrics.Constants.cpWatLiq "Specific heat capacity"; final parameter Modelica.Units.SI.MassFlowRate m_flow_nominal(min=0)= Q_flow_nominal/cp/dT_nominal "Mass flow rate at nominal conditions"; Buildings.Controls.OBC.CDL.Interfaces.RealInput loa(final unit="W") "Signal approximating the load on condenser or evaporator"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput m_flow(final unit="kg/s") "Mass flow rate"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant masFloMin( final k=ratFloMin*m_flow_nominal) "Minimum mass flow rate"; Buildings.Controls.OBC.CDL.Continuous.MultiplyByParameter masFlo_dT(final k=1 /cp/dT_nominal) "Mass flow rate for constant DeltaT"; Buildings.Controls.OBC.CDL.Continuous.Max masFlo "Mass flow rate"; Buildings.Controls.OBC.CDL.Continuous.Abs abs1 "Absolute value"; equation connect(loa, masFlo_dT.u); connect(masFloMin.y, masFlo.u1); connect(masFlo.y, m_flow); connect(masFlo_dT.y, abs1.u); connect(abs1.y, masFlo.u2); end PrimaryVariableFlow;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Reset

Supervisory supply temperature reset

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Reset

Information

This block implements the supervisory reset of the heating water supply temperature. The heating water supply temperature is reset down whenever the heating demand signal yielded by the building automation system is false. This enables operating the chiller at a reduced lift whenever there is no requirement on the water temperature supplied to the building system.

Note that the chilled water supply temperature is not reset for the sake of simplicity. It would indeed require a more involved algorithm preventing the reset in case it limits the cold rejection capacity considering the actual district water temperature.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Temperature	THeaWatSupSetMin		Minimum value of heating water supply temperature set point [K]

Connectors

Type	Name	Description
input BooleanInput	uHea	Heating enable signal
input RealInput	THeaWatSupPreSet	Heating water supply temperature set point [K]
output RealOutput	THeaWatSupSet	Heating water supply temperature set point after reset [K]

Modelica definition

model Reset "Supervisory supply temperature reset" extends Modelica.Blocks.Icons.Block; parameter Modelica.Units.SI.Temperature THeaWatSupSetMin(displayUnit="degC") "Minimum value of heating water supply temperature set point"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uHea "Heating enable signal"; Buildings.Controls.OBC.CDL.Interfaces.RealInput THeaWatSupPreSet( final unit="K", displayUnit="degC") "Heating water supply temperature set point"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput THeaWatSupSet( final unit="K", displayUnit="degC") "Heating water supply temperature set point after reset"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant minSet( k=THeaWatSupSetMin) "Minimum value of HW set point"; Buildings.Controls.OBC.CDL.Continuous.Switch swiHea "Switch"; Buildings.Controls.OBC.CDL.Continuous.LimitSlewRate ramLimHea(raisingSlewRate= 0.1) "Limit the rate of change"; equation connect(THeaWatSupPreSet,swiHea.u1); connect(minSet.y,swiHea.u3); connect(uHea,swiHea.u2); connect(swiHea.y,ramLimHea.u); connect(ramLimHea.y,THeaWatSupSet); end Reset;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideCold

Control block for cold side

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideCold

Information

This block serves as the controller for the cold side of the ETS in Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Supervisory. It computes the following control signals.

Control signals for ambient sources yAmb (array)
The cold rejection control signal yielded by the hot side controller is processed as follows.
- A controller is used to track the chilled water supply temperature (CHWST) set point. This controller is enabled when cooling is enabled. It yields a control signal value between 0 and nSouAmb.
- The systems serving as ambient sources are then controlled in sequence by mapping the minimum between the CHWST control loop output and the part of the cold rejection signal between 0 and nSouAmb to a nSouAmb-array of signals between 0 and 1.
Chilled water supply temperature set point TChiWatSupSet
The remaining part of the cold rejection signal between nSouAmb and nSouAmb+1 is used to reset the CHWST set point between a maximum value provided as an input variable, and a minimum value provided as a parameter.
Control signal for the evaporator loop isolation valve yIsoAmb
The valve is commanded to be fully open whenever the cold rejection control signal is greater than zero. The command signal is held for 60s to avoid short cycling.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Integer	nSouAmb	1	Number of ambient sources to control
Temperature	TChiWatSupSetMin		Minimum value of chilled water supply temperature set point [K]
SimpleController	controllerType	Buildings.Controls.OBC.CDL.T...	Type of controller
Real	k	0.1	Gain of controller
Time	Ti	120	Time constant of integrator block [s]

Connectors

Type	Name	Description
input RealInput	uCol	Cold rejection control signal
output RealOutput	TChiWatSupSet	Chilled water supply temperature set point [K]
input BooleanInput	uHeaCoo	Enable signal for heating or cooling
input RealInput	TSet	Supply temperature set point (heating or chilled water) [K]
input RealInput	TBot	Temperature at bottom of tank [K]
output RealOutput	yAmb[nSouAmb]	Control signal for ambient sources [1]
output RealOutput	yValIso	Ambient loop isolation valve control signal [1]

Modelica definition

model SideCold "Control block for cold side" extends Modelica.Blocks.Icons.Block; parameter Integer nSouAmb=1 "Number of ambient sources to control"; parameter Modelica.Units.SI.Temperature TChiWatSupSetMin(displayUnit="degC") "Minimum value of chilled water supply temperature set point"; parameter Buildings.Controls.OBC.CDL.Types.SimpleController controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI "Type of controller"; parameter Real k( min=0)=0.1 "Gain of controller"; parameter Modelica.Units.SI.Time Ti( min=Buildings.Controls.OBC.CDL.Constants.small)=120 "Time constant of integrator block"; Buildings.Controls.OBC.CDL.Interfaces.RealInput uCol "Cold rejection control signal"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput TChiWatSupSet( final unit="K", displayUnit="degC") "Chilled water supply temperature set point"; Buildings.Controls.OBC.CDL.Continuous.Line mapFun[nSouAmb] "Mapping functions for ambient source control"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant x1[nSouAmb]( final k={(i-1) for i in 1:nSouAmb}) "x1"; Buildings.Controls.OBC.CDL.Routing.RealScalarReplicator rep( final nout=nSouAmb) "Replicate control signal"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant f1[nSouAmb]( each final k=0) "f1"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant f2[nSouAmb]( each final k=1) "f2"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant x2[nSouAmb]( final k={(i) for i in 1:nSouAmb}) "x2"; Combined.Controls.PIDWithEnable conTChiWatSup( final k=k, final Ti=Ti, final controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI, final yMin=0, final yMax=1, final reverseActing=false) "Controller for CHWST"; Buildings.Controls.OBC.CDL.Continuous.Line mapFunTChiSupSet "Mapping function for CHWST reset"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant minTChiWatSup( y(final unit="K", displayUnit="degC"), final k=TChiWatSupSetMin) "Minimum value of chilled water supply temperature"; Buildings.Controls.OBC.CDL.Continuous.AddParameter addPar( p=nSouAmb) "One minus control loop output"; Buildings.Controls.OBC.CDL.Continuous.MultiplyByParameter gai( k=-nSouAmb) "Gain factor"; Buildings.Controls.OBC.CDL.Continuous.Max max1 "CHWST reset signal"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant zer( k=0) "Zero"; Buildings.Controls.OBC.CDL.Continuous.AddParameter subNumSou( p=-nSouAmb) "Control signal minus nSouAmb"; Buildings.Controls.OBC.CDL.Continuous.Min min1 "Ambient source control signal"; Buildings.Controls.OBC.CDL.Continuous.LimitSlewRate ramLimHea( raisingSlewRate=0.1) "Limit the rate of change"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uHeaCoo "Enable signal for heating or cooling"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TSet( final unit="K", displayUnit="degC") "Supply temperature set point (heating or chilled water)"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TBot( final unit="K", displayUnit="degC") "Temperature at bottom of tank"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yAmb[nSouAmb]( each final unit="1") "Control signal for ambient sources"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yValIso( final unit="1") "Ambient loop isolation valve control signal"; Buildings.Controls.OBC.CDL.Conversions.BooleanToReal booToRea "Convert DO to AO signal"; Buildings.Controls.OBC.CDL.Continuous.GreaterThreshold greThr( t=0.01) "Control signal is non zero (with 1% tolerance)"; Modelica.Blocks.Discrete.ZeroOrderHold zeroOrderHold( samplePeriod=60); equation connect(x1.y,mapFun.x1); connect(rep.y,mapFun.u); connect(f1.y,mapFun.f1); connect(f2.y,mapFun.f2); connect(x2.y,mapFun.x2); connect(TSet,conTChiWatSup.u_s); connect(TBot,conTChiWatSup.u_m); connect(f2[1].y,mapFunTChiSupSet.x2); connect(minTChiWatSup.y,mapFunTChiSupSet.f2); connect(TSet,mapFunTChiSupSet.f1); connect(uCol,subNumSou.u); connect(max1.y,mapFunTChiSupSet.u); connect(uCol,min1.u1); connect(addPar.y,min1.u2); connect(min1.y,rep.u); connect(mapFun.y,yAmb); connect(ramLimHea.y,TChiWatSupSet); connect(uHeaCoo,conTChiWatSup.uEna); connect(zer.y,mapFunTChiSupSet.x1); connect(uCol,greThr.u); connect(greThr.y,booToRea.u); connect(booToRea.y,zeroOrderHold.u); connect(zeroOrderHold.y,yValIso); connect(mapFunTChiSupSet.y,ramLimHea.u); connect(zer.y,max1.u2); connect(subNumSou.y,max1.u1); connect(conTChiWatSup.y, gai.u); connect(gai.y, addPar.u); end SideCold;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideHot

Control block for hot side

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideHot

Information

This block serves as the controller for the hot side of the ETS in Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Supervisory. It computes the following control signals.

Control signals for ambient sources yAmb (array)
The controller for heat rejection is enabled when the return position of the evaporator loop isolation valve is close to zero. When enabled, it maintains the temperature at the top of the heating water tank at the heating water supply temperature set point plus a dead band dTDea. The controller yields a control signal value between 0 and nSouAmb. The systems serving as ambient sources are then controlled in sequence by mapping the controller output to a nSouAmb-array of signals between 0 and 1.
Control signal for cold rejection yCol
The controller for cold rejection is enabled if
- the return position of the condenser loop isolation valve is close to zero, and
- heating is enabled, and
- the temperature at the top of the heating water tank is below a safety limit equal to the heating water supply temperature set point plus the parameter dTLoc. This last condition limits the temperature overshoot after the warmup periods, without having to finely tune the heat and cold rejection controller parameters to guard against the disturbing effect of a varying district water temperature.
When enabled, the controller maintains the temperature at the top of the heating water tank at the heating water supply temperature set point. The controller yields a signal between 0 and nSouAmb+1 which is connected to Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideCold where it is used to control in sequence the systems serving as ambient sources and ultimately to reset down the chilled water supply temperature.
Control signal for the condenser loop isolation valve yIsoAmb
The valve is commanded to be fully open whenever the controller for heat rejection yields an output signal greater than zero. The command signal is held for 60s to avoid short cycling.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Integer	nSouAmb	1	Number of ambient sources to control
TemperatureDifference	dTDea	1	Temperature difference band between set point tracking and heat rejection (absolute value) [K]
TemperatureDifference	dTLoc	dTDea + 2	Temperature difference between set point tracking and cold rejection lockout (absolute value) [K]
SimpleController	controllerType	Buildings.Controls.OBC.CDL.T...	Type of controller
Real	k	0.1	Gain of controller
Time	Ti	120	Time constant of integrator block [s]

Connectors

Type	Name	Description
output RealOutput	yCol	Control signal for cold side [1]
input BooleanInput	uHeaCoo	Enable signal for heating or cooling
input RealInput	TSet	Supply temperature set point (heating or chilled water) [K]
input RealInput	TTop	Temperature at top of tank [K]
output RealOutput	yAmb[nSouAmb]	Control signal for ambient sources [1]
output RealOutput	yValIso	Ambient loop isolation valve control signal [1]
input RealInput	yValIsoCon_actual	Return position of condenser to ambient loop isolation valve [1]
input RealInput	yValIsoEva_actual	Return position of evaporator to ambient loop isolation valve [1]

Modelica definition

block SideHot "Control block for hot side" extends Modelica.Blocks.Icons.Block; parameter Integer nSouAmb=1 "Number of ambient sources to control"; parameter Modelica.Units.SI.TemperatureDifference dTDea(min=0) = 1 "Temperature difference band between set point tracking and heat rejection (absolute value)"; parameter Modelica.Units.SI.TemperatureDifference dTLoc(min=0) = dTDea + 2 "Temperature difference between set point tracking and cold rejection lockout (absolute value)"; parameter Buildings.Controls.OBC.CDL.Types.SimpleController controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI "Type of controller"; parameter Real k( min=0)=0.1 "Gain of controller"; parameter Modelica.Units.SI.Time Ti(min=Buildings.Controls.OBC.CDL.Constants.small)= 120 "Time constant of integrator block"; PIDWithEnable conColRej( final k=k, final Ti=Ti, final controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI, final yMin=0, final yMax=nSouAmb+1, final reverseActing=true) "Controller for cold rejection"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yCol( final unit="1") "Control signal for cold side"; Buildings.Controls.OBC.CDL.Continuous.GreaterThreshold greThr( final t=0.01) "Control signal is non zero (with 1% tolerance)"; Buildings.Controls.OBC.CDL.Conversions.BooleanToReal booToRea "Convert DO to AO signal"; PIDWithEnable conHeaRej( final k=k, final Ti=Ti, final controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI, final yMin=0, final yMax=nSouAmb, final reverseActing=false) "Controller for heat rejection"; Buildings.Controls.OBC.CDL.Continuous.Line mapFun[nSouAmb] "Mapping functions for controlled systems"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant x1[nSouAmb]( final k={(i-1) for i in 1:nSouAmb}) "x1"; Buildings.Controls.OBC.CDL.Routing.RealScalarReplicator rep( final nout=nSouAmb) "Replicate control signal"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant f1[nSouAmb]( each final k=0) "f1"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant f2[nSouAmb]( each final k=1) "f2"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant x2[nSouAmb]( final k={(i) for i in 1:nSouAmb}) "x2"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uHeaCoo "Enable signal for heating or cooling"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TSet( final unit="K", displayUnit="degC") "Supply temperature set point (heating or chilled water)"; Buildings.Controls.OBC.CDL.Interfaces.RealInput TTop( final unit="K", displayUnit="degC") "Temperature at top of tank"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yAmb[nSouAmb]( each final unit="1") "Control signal for ambient sources"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yValIso( final unit="1") "Ambient loop isolation valve control signal"; Buildings.Controls.OBC.CDL.Interfaces.RealInput yValIsoCon_actual( final unit="1") "Return position of condenser to ambient loop isolation valve"; Buildings.Controls.OBC.CDL.Interfaces.RealInput yValIsoEva_actual( final unit="1") "Return position of evaporator to ambient loop isolation valve"; Buildings.Controls.OBC.CDL.Continuous.LessThreshold isValIsoConClo( final t=1E-6, h=0.5E-6) "Check if isolation valve is closed"; Buildings.Controls.OBC.CDL.Continuous.LessThreshold isValIsoEvaClo( final t=1E-6, h=0.5E-6) "At least one signal is non zero"; Buildings.Controls.OBC.CDL.Logical.MultiAnd mulAnd( nin=3); Buildings.Controls.OBC.CDL.Continuous.AddParameter addDea( p=dTDea) "Add dead band"; Modelica.Blocks.Discrete.ZeroOrderHold zeroOrderHold( samplePeriod=60); Buildings.Controls.OBC.CDL.Continuous.AddParameter addLoc( p=dTLoc) "Add temperature difference for lockout"; Buildings.Controls.OBC.CDL.Continuous.Less isBelLoc( h=0.1) "Check if temperature is below cold rejection lockout"; equation connect(mapFun.y,yAmb); connect(TSet,conColRej.u_s); connect(TTop,conColRej.u_m); connect(conHeaRej.y,greThr.u); connect(x1.y,mapFun.x1); connect(conHeaRej.y,rep.u); connect(rep.y,mapFun.u); connect(f1.y,mapFun.f1); connect(f2.y,mapFun.f2); connect(x2.y,mapFun.x2); connect(conColRej.y,yCol); connect(TTop,conHeaRej.u_m); connect(yValIsoCon_actual,isValIsoConClo.u); connect(yValIsoEva_actual,isValIsoEvaClo.u); connect(mulAnd.y,conColRej.uEna); connect(isValIsoEvaClo.y,conHeaRej.uEna); connect(TSet,addDea.u); connect(addDea.y,conHeaRej.u_s); connect(greThr.y,booToRea.u); connect(booToRea.y,zeroOrderHold.u); connect(zeroOrderHold.y,yValIso); connect(TSet,addLoc.u); connect(TTop,isBelLoc.u1); connect(addLoc.y,isBelLoc.u2); connect(uHeaCoo,mulAnd.u[1]); connect(isValIsoConClo.y,mulAnd.u[2]); connect(isBelLoc.y,mulAnd.u[3]); end SideHot;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Supervisory

Supervisory controller

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Supervisory

Information

This block implements the supervisory control functions of the ETS model Buildings.Experimental.DHC.EnergyTransferStations.Combined.ChillerBorefield.

Heating (resp. cooling) is enabled based on the input signal uHea (resp. uCoo) which is held for 15', meaning that, when enabled, the mode remains active for at least 15 minutes and, when disabled, the mode cannot be enabled again for at least 15 minutes. The heating and cooling enable signals should be computed externally based on a schedule (to lock out the system during off-hours), ideally in conjunction with the number of requests yielded by the terminal unit controllers, or any other signal representative of the load. Indeed, the heating water supply set point is allowed to be reset down only when heating is disabled, in which case the system performance is improved due to a lower chiller lift.
The controller resets the heating water supply temperature based on the logic described in Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.Reset. Note that this resetting logic is meant to operate the chiller at low lift. The chilled water supply temperature may be also reset down by Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideCold to maintain the heating water supply temperature set point. This second resetting logic is required for the heating function of the unit, but it has a negative impact on the lift.
Eventually the systems serving as ambient sources are controlled based on the maximum of the control signals yAmb yielded by Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideHot and Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SideCold.

Extends from Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.BaseClasses.PartialSupervisory (Partial model for supervisory controller).

Parameters

Type	Name	Default	Description
Integer	nSouAmb		Number of ambient sources to control
SimpleController	controllerType	Buildings.Controls.OBC.CDL.T...	Type of controller
Real	kHot	0.05	Gain of controller on hot side
Real	kCol	0.1	Gain of controller on cold side
Time	TiHot	300	Time constant of integrator block on hot side [s]
Time	TiCol	120	Time constant of integrator block on cold side [s]
Temperature	THeaWatSupSetMin		Minimum value of heating water supply temperature set point [K]
Temperature	TChiWatSupSetMin		Minimum value of chilled water supply temperature set point [K]

Connectors

Type	Name	Description
input BooleanInput	uHea	Heating enable signal
input BooleanInput	uCoo	Cooling enable signal
input RealInput	TChiWatSupPreSet	Chilled water supply temperature set point [K]
input RealInput	TChiWatBot	Chilled water temperature at tank bottom [K]
input RealInput	THeaWatTop	Heating water temperature at tank top [K]
input RealInput	THeaWatSupPreSet	Heating water supply temperature set point [K]
output RealOutput	THeaWatSupSet	Heating water supply temperature set point after reset [K]
output RealOutput	TChiWatSupSet	Chilled water supply temperature set point after reset [K]
output RealOutput	yValIsoEva	Evaporator to ambient loop isolation valve control signal [1]
output RealOutput	yValIsoCon	Condenser to ambient loop isolation valve control signal [1]
output RealOutput	yAmb[nSouAmb]	Control output for ambient sources [1]
output BooleanOutput	yHea	Tank in heating demand
output BooleanOutput	yCoo	Tank in cooling demand
input RealInput	yValIsoCon_actual	Return position of condenser to ambient loop isolation valve [1]
input RealInput	yValIsoEva_actual	Return position of evaporator to ambient loop isolation valve [1]

Modelica definition

model Supervisory "Supervisory controller" extends Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.BaseClasses.PartialSupervisory; parameter Buildings.Controls.OBC.CDL.Types.SimpleController controllerType=Buildings.Controls.OBC.CDL.Types.SimpleController.PI "Type of controller"; parameter Real kHot( min=0)=0.05 "Gain of controller on hot side"; parameter Real kCol( min=0)=0.1 "Gain of controller on cold side"; parameter Modelica.Units.SI.Time TiHot(min=Buildings.Controls.OBC.CDL.Constants.small)= 300 "Time constant of integrator block on hot side"; parameter Modelica.Units.SI.Time TiCol(min=Buildings.Controls.OBC.CDL.Constants.small)= 120 "Time constant of integrator block on cold side"; parameter Modelica.Units.SI.Temperature THeaWatSupSetMin(displayUnit="degC") "Minimum value of heating water supply temperature set point"; parameter Modelica.Units.SI.Temperature TChiWatSupSetMin(displayUnit="degC") "Minimum value of chilled water supply temperature set point"; Buildings.Controls.OBC.CDL.Interfaces.RealInput yValIsoCon_actual( final unit="1") "Return position of condenser to ambient loop isolation valve"; Buildings.Controls.OBC.CDL.Interfaces.RealInput yValIsoEva_actual( final unit="1") "Return position of evaporator to ambient loop isolation valve"; Combined.Controls.SideHot conHot( final k=kHot, final Ti=TiHot, final nSouAmb=nSouAmb, final controllerType=controllerType) "Hot side controller"; SideCold conCol( final k=kCol, final Ti=TiCol, final nSouAmb=nSouAmb, final controllerType=controllerType, final TChiWatSupSetMin=TChiWatSupSetMin) "Cold side controller"; Buildings.Controls.OBC.CDL.Continuous.Max max1[nSouAmb] "Maximum of output control signals"; Reset resTSup( final THeaWatSupSetMin=THeaWatSupSetMin) "Supply temperature reset"; equation connect(conHot.yAmb,max1.u1); connect(conCol.yAmb,max1.u2); connect(conHot.yCol,conCol.uCol); connect(resTSup.THeaWatSupSet,conHot.TSet); connect(THeaWatTop,conHot.TTop); connect(max1.y,yAmb); connect(TChiWatBot,conCol.TBot); connect(THeaWatSupPreSet,resTSup.THeaWatSupPreSet); connect(conHot.yValIso,yValIsoCon); connect(conCol.yValIso,yValIsoEva); connect(resTSup.THeaWatSupSet,THeaWatSupSet); connect(conCol.TChiWatSupSet,TChiWatSupSet); connect(TChiWatSupPreSet,conCol.TSet); connect(uHeaHol.y,conHot.uHeaCoo); connect(uCooHol.y,conCol.uHeaCoo); connect(uHeaHol.y,resTSup.uHea); connect(uHeaHol.y,yHea); connect(uCooHol.y,yCoo); connect(yValIsoCon_actual,conHot.yValIsoCon_actual); connect(yValIsoEva_actual,conHot.yValIsoEva_actual); end Supervisory;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SwitchBox

Controller for flow switch box

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.SwitchBox

Information

This block implements a control logic preventing flow reversal in the service line, for instance with the hydronic configuration of Buildings.Experimental.DHC.EnergyTransferStations.Combined.HeatPumpHeatExchanger. The block requires two input signals representing the mass flow rate contributing to a positive flow direction mPos_flow and the mass flow contributing to a reverse flow direction mRev_flow. The output signal y switches to maintain mPos_flow ≥ mRev_flow with a temporization avoiding short cycling. Due to the temporization, the mass flow rate may transiently change direction as illustrated in Buildings.Experimental.DHC.EnergyTransferStations.Combined.Subsystems.Validation.SwitchBox.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Real	trueHoldDuration		true hold duration [s]
Real	falseHoldDuration	trueHoldDuration	false hold duration [s]

Connectors

Type	Name	Description
input RealInput	mPos_flow	Service water mass flow rate in positive direction [kg/s]
input RealInput	mRev_flow	Service water mass flow rate in reverse direction [kg/s]
output RealOutput	y	Control output signal [1]

Modelica definition

block SwitchBox "Controller for flow switch box" extends Modelica.Blocks.Icons.Block; parameter Real trueHoldDuration( final quantity="Time", final unit="s") "true hold duration"; parameter Real falseHoldDuration( final quantity="Time", final unit="s") = trueHoldDuration "false hold duration"; Buildings.Controls.OBC.CDL.Interfaces.RealInput mPos_flow(final unit="kg/s") "Service water mass flow rate in positive direction"; Buildings.Controls.OBC.CDL.Interfaces.RealInput mRev_flow(final unit="kg/s") "Service water mass flow rate in reverse direction"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput y(final unit="1") "Control output signal"; Modelica.Blocks.Logical.GreaterEqual posDom "Output true in case of dominating positive flow"; Modelica.Blocks.Logical.Switch swi "Switch to select the mode"; Modelica.Blocks.Sources.Constant posModOn(final k=1) "Output signal in case of dominating positive flow"; Buildings.Controls.OBC.CDL.Logical.TrueFalseHold truFalHol( final trueHoldDuration=trueHoldDuration, final falseHoldDuration=falseHoldDuration) "True/false hold to remove the risk of chattering"; Modelica.Blocks.Sources.Constant revModOn(final k=0) "Output signal in case of dominating reverse flow"; equation connect(posModOn.y, swi.u1); connect(swi.y, y); connect(mRev_flow, posDom.u2); connect(posDom.y, truFalHol.u); connect(truFalHol.y, swi.u2); connect(mPos_flow, posDom.u1); connect(revModOn.y, swi.u3); end SwitchBox;

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.WatersideEconomizer

Waterside economizer controller

Buildings.Experimental.DHC.EnergyTransferStations.Combined.Controls.WatersideEconomizer

Information

This block implements the control logic for the waterside economizer.

The system is enabled if

it has been disabled for more than 20 minutes, and
the "cooling enabled" input signal is true, and
the evaporator isolation valve is closed (i.e., the system is not in cold rejection mode), and
the predicted leaving water temperature is lower than the entering water temperature minus dTEna.

The system is disabled if

it has been enabled for more than 20 minutes, and
the "cooling enabled" input signal is false, or
the evaporator isolation valve is open, or
the leaving water temperature is higher than the entering water temperature minus dTDis.

When the system is enabled

the primary side is controlled so that the primary flow rate varies linearly with the secondary flow rate,
the bypass valve on the secondary side is fully closed.

When the system is disabled

if the "cooling enabled" input signal is true and the evaporator isolation valve is closed, the primary pump (resp. valve) is operated at its minimum speed (resp. opening), otherwise it is switched off (resp. fully closed): this is needed to yield a representative measurement of the service water entering temperature,
the bypass valve on the secondary side is fully open.

Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Parameters

Type	Name	Default	Description
Nominal condition
MassFlowRate	m2_flow_nominal		Heat exchanger secondary mass flow rate [kg/s]
Temperature	T_a1_nominal		Nominal water inlet temperature on district side [K]
Temperature	T_b2_nominal		Nominal water outlet temperature on building side [K]
Controls
Real	y1Min	0.05	Minimum pump flow rate or valve opening for temperature measurement (fractional) [1]
TemperatureDifference	dTEna	1	Minimum delta-T above predicted heat exchanger leaving water temperature to enable WSE [K]
TemperatureDifference	dTDis	0.5	Minimum delta-T across heat exchanger before disabling WSE [K]

Connectors

Type	Name	Description
input RealInput	T1WatEnt	Heat exchanger primary water entering temperature [K]
input RealInput	m2_flow	Heat exchanger secondary mass flow rate [kg/s]
input RealInput	T2WatLvg	Heat exchanger secondary water leaving temperature [K]
input RealInput	T2WatEnt	Heat exchanger secondary water entering temperature [K]
output RealOutput	y1	Primary control signal (pump or valve) [1]
output RealOutput	yVal2	Secondary valve control signal [1]
input BooleanInput	uCoo	Cooling enable signal
input RealInput	yValIsoEva_actual	Return position of evaporator to ambient loop isolation valve [1]

Modelica definition

model WatersideEconomizer "Waterside economizer controller" extends Modelica.Blocks.Icons.Block; parameter Modelica.Units.SI.MassFlowRate m2_flow_nominal "Heat exchanger secondary mass flow rate"; parameter Modelica.Units.SI.Temperature T_a1_nominal "Nominal water inlet temperature on district side"; parameter Modelica.Units.SI.Temperature T_b2_nominal "Nominal water outlet temperature on building side"; parameter Real y1Min(final unit="1")=0.05 "Minimum pump flow rate or valve opening for temperature measurement (fractional)"; parameter Modelica.Units.SI.TemperatureDifference dTEna=1 "Minimum delta-T above predicted heat exchanger leaving water temperature to enable WSE"; parameter Modelica.Units.SI.TemperatureDifference dTDis=0.5 "Minimum delta-T across heat exchanger before disabling WSE"; Buildings.Controls.OBC.CDL.Interfaces.RealInput T1WatEnt( final unit="K", displayUnit="degC") "Heat exchanger primary water entering temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput m2_flow( final unit="kg/s") "Heat exchanger secondary mass flow rate"; Buildings.Controls.OBC.CDL.Interfaces.RealInput T2WatLvg( final unit="K", displayUnit="degC") "Heat exchanger secondary water leaving temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealInput T2WatEnt( final unit="K", displayUnit="degC") "Heat exchanger secondary water entering temperature"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput y1(final unit="1") "Primary control signal (pump or valve)"; Buildings.Controls.OBC.CDL.Interfaces.RealOutput yVal2( final unit="1") "Secondary valve control signal"; Buildings.Controls.OBC.CDL.Continuous.AddParameter addDelTem( final p=dTEna) "Add threshold for enabling WSE"; Modelica.StateGraph.InitialStepWithSignal iniSta(nIn=1, nOut=1) "Initial state "; Modelica.StateGraph.TransitionWithSignal ena "Transition to enabled state"; Modelica.StateGraph.StepWithSignal actSta(nIn=1, nOut=1) "Active WSE"; Modelica.StateGraph.TransitionWithSignal dis "Transition to disabled state"; Buildings.Controls.OBC.CDL.Continuous.Subtract delT1 "Add delta-T"; Buildings.Controls.OBC.CDL.Continuous.LessThreshold delTemDis(t=dTDis) "Compare to threshold for disabling WSE"; PredictLeavingTemperature calTemLvg( final dTApp_nominal=abs(T_a1_nominal - T_b2_nominal), final m2_flow_nominal=m2_flow_nominal) "Compute predicted leaving water temperature"; Buildings.Controls.OBC.CDL.Continuous.Less delTemDis1 "Compare to threshold for enabling WSE"; Buildings.Controls.OBC.CDL.Conversions.BooleanToReal booToRea( final realTrue=1, final realFalse=0) "Convert to real signal (close bypass valve when WSE enabled)"; inner Modelica.StateGraph.StateGraphRoot stateGraphRoot "Root of state graph"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant min1( final k=y1Min) "Minimum signal"; Buildings.Controls.OBC.CDL.Continuous.Line lin "Linear variation bounded by minimum and 1"; Buildings.Controls.OBC.CDL.Continuous.Switch swiOff1 "Output zero if cooling not enabled or isolation valve open (cold rejection)"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant zer(final k=0) "Zero"; Buildings.Controls.OBC.CDL.Interfaces.BooleanInput uCoo "Cooling enable signal"; Buildings.Controls.OBC.CDL.Logical.MultiAnd mulAnd(nin=4) "Enable if cooling enabled and temperature criterion verified"; Buildings.Controls.OBC.CDL.Logical.MultiOr or1(nin=3) "Cooling disabled or temperature criterion verified"; Buildings.Controls.OBC.CDL.Logical.Not not2 "Cooling disabled"; Buildings.Controls.OBC.CDL.Logical.Timer tim(t=1200) "True when WSE active for more than t"; Buildings.Controls.OBC.CDL.Logical.Timer tim1(t=1200) "True when WSE inactive for more than t"; Buildings.Controls.OBC.CDL.Logical.And and2 "Cooling disabled or temperature criterion verified"; Buildings.Controls.OBC.CDL.Continuous.LessThreshold isValIsoEvaClo( final t=1E-6, h=0.5E-6) "True if valve closed"; Buildings.Controls.OBC.CDL.Interfaces.RealInput yValIsoEva_actual(final unit="1") "Return position of evaporator to ambient loop isolation valve"; Buildings.Controls.OBC.CDL.Logical.Not not1 "True if valve open"; Buildings.Controls.OBC.CDL.Logical.And and1 "Cooling disabled or temperature criterion verified"; Buildings.Controls.OBC.CDL.Continuous.MultiplyByParameter nor2( k=1/m2_flow_nominal) "Normalize"; Buildings.Controls.OBC.CDL.Continuous.Switch swiOff2 "Switch between enabled and disabled mode"; Buildings.Controls.OBC.CDL.Continuous.Sources.Constant one(final k=1) "One"; equation connect(T2WatEnt, delT1.u1); connect(T2WatLvg, delT1.u2); connect(delT1.y, delTemDis.u); connect(T1WatEnt, calTemLvg.T1WatEnt); connect(calTemLvg.T2WatLvg, addDelTem.u); connect(addDelTem.y, delTemDis1.u1); connect(T2WatEnt, delTemDis1.u2); connect(iniSta.outPort[1], ena.inPort); connect(ena.outPort, actSta.inPort[1]); connect(actSta.outPort[1], dis.inPort); connect(dis.outPort, iniSta.inPort[1]); connect(booToRea.y, yVal2); connect(zer.y, swiOff1.u3); connect(mulAnd.y, ena.condition); connect(uCoo, not2.u); connect(actSta.active, booToRea.u); connect(delTemDis1.y, mulAnd.u[1]); connect(iniSta.active, tim1.u); connect(tim1.passed, mulAnd.u[2]); connect(uCoo, mulAnd.u[3]); connect(actSta.active, tim.u); connect(tim.passed, and2.u1); connect(or1.y, and2.u2); connect(and2.y, dis.condition); connect(m2_flow, calTemLvg.m2_flow); connect(yValIsoEva_actual,isValIsoEvaClo.u); connect(isValIsoEvaClo.y, mulAnd.u[4]); connect(isValIsoEvaClo.y, not1.u); connect(delTemDis.y, or1.u[1]); connect(not2.y, or1.u[2]); connect(not1.y, or1.u[3]); connect(uCoo, and1.u1); connect(and1.y, swiOff1.u2); connect(isValIsoEvaClo.y, and1.u2); connect(m2_flow, nor2.u); connect(min1.y, swiOff1.u1); connect(swiOff2.y, y1); connect(swiOff1.y, swiOff2.u1); connect(iniSta.active, swiOff2.u2); connect(lin.y, swiOff2.u3); connect(nor2.y, lin.u); connect(one.y, lin.x2); connect(one.y, lin.f2); connect(zer.y, lin.x1); connect(min1.y, lin.f1); end WatersideEconomizer;