Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses

Package with base classes for Buildings.Fluid.HeatPump.Controls.Safety

Information

This package contains base classes that are used to construct the models in Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety

Package Content

Name	Description
BoundaryMap	Block that checks if the inputs are within the characteristic map
CycleRateBoundary	Checks if the cycle rate is in boundary
OnOffFuzzyLogic	Fuzzy logic approach for on-off control
OnPastThreshold	Returns true if the device stays on for longer than a threshold time
PartialOperationalEnvelope	Indicates if the device operation is within a defined envelope
PartialSafety	Safety control with I/O
PartialSafetyWithCounter	Safety control which adds an error counter to the I/O

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.BoundaryMap

Block that checks if the inputs are within the characteristic map

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.BoundaryMap

Information

Given an input of TCon and TEva, the model returns false if the given point is outside of the given operational envelope.

The maximal and minimal TCon depend on TEva and are defined by the upper and lower boundaries in form of 1Ds-Tables.

The maximal and minimal TEva values are obtained trough the table and are constant.

For the boundaries of the TCon input value, a dynamic hysteresis is used to ensure a used device will stay off a certain time after shutdown.

This is similar to the hysteresis in a pressure-based safety control, which prevents operation outside this envelope in real devices.

Parameters

Type	Name	Description
Real	tab[:, 2]	Table for boundary with second column as useful temperature side
TemperatureDifference	dT	Delta value used to avoid state events when used as a safety control [K]
Boolean	isUppBou	=true if it is an upper boundary, false for lower

Connectors

Type	Name	Description
output BooleanOutput	noErr	=false when an error occurs
input RealInput	TAmbSid	Temperature at ambient side [K]
input RealInput	TUseSid	Useful temperature side [K]

Modelica definition

model BoundaryMap "Block that checks if the inputs are within the characteristic map" parameter Real tab[:,2] "Table for boundary with second column as useful temperature side"; parameter Modelica.Units.SI.TemperatureDifference dT "Delta value used to avoid state events when used as a safety control"; parameter Boolean isUppBou "=true if it is an upper boundary, false for lower"; Modelica.Blocks.Interfaces.BooleanOutput noErr "=false when an error occurs"; Modelica.Blocks.Interfaces.RealInput TAmbSid(unit="K", displayUnit="degC") "Temperature at ambient side"; Modelica.Blocks.Tables.CombiTable1Ds tabBou( final table=tab, final smoothness=Modelica.Blocks.Types.Smoothness.LinearSegments, final tableOnFile=false) "Table with envelope data"; Modelica.Blocks.MathBoolean.Nor nor(nu=3) "=true if the operational envelope is not violated"; Modelica.Blocks.Logical.Hysteresis hysLef( final uLow=-0.05, final uHigh=0, pre_y_start=false) "Hysteresis for left side of envelope"; Modelica.Blocks.Logical.Hysteresis hysRig( final uLow=-0.05, final uHigh=0, pre_y_start=false) "Hysteresis for right side of envelope"; Modelica.Blocks.Sources.Constant conTAmbSidMin(k=TAmbSidMin) "Constant minimal temperature of ambient temperature side"; Modelica.Blocks.Sources.Constant conTAmbSidMax(k=TAmbSidMax) "Constant maximal temperature of ambient temperature side"; Modelica.Blocks.Math.Add subMax(final k1=+1, final k2=-1) "Actual minus maximal ambient side temperature"; Modelica.Blocks.Math.Add sub(final k1=-1, final k2=+1) "Minimal minus current ambient side temperature"; Modelica.Blocks.Interfaces.RealInput TUseSid(unit="K", displayUnit="degC") "Useful temperature side "; Modelica.Blocks.Math.Add subBou(final k1=if isUppBou then 1 else -1, final k2= if isUppBou then -1 else 1) "Subtract boundary from current value depending on lower or upper boundary"; Modelica.Blocks.Logical.Hysteresis hysBou( final uLow=-dT, final uHigh=0, pre_y_start=false) "Hysteresis for temperature limit"; protected parameter Real icoMin=-70 "Used to set the frame where the icon should appear"; parameter Real icoMax=70 "Used to set the frame where the icon should appear"; final parameter Modelica.Units.SI.Temperature TAmbSidMax=tab[end, 1] "Maximal value of ambient side"; final parameter Modelica.Units.SI.Temperature TAmbSidMin=tab[1, 1] "Minimal temperature at ambient side"; final parameter Modelica.Units.SI.Temperature TUseSidMax=max(tab[:, 2]) "Maximal temperature of useful side"; final parameter Modelica.Units.SI.Temperature TUseSidMin=0 "Minimal value of useful side"; final parameter Real poi[size(scaTAmbSid, 1),2]=transpose({scaTAmbSidToPoi, scaTUseSidToPoi}) "Points for dynamic annotation"; final parameter Modelica.Units.SI.Temperature scaTAmbSid[:]=tab[:, 1] "Helper array with only not ambient side temperature values"; final parameter Modelica.Units.SI.Temperature scaTUseSid[:]=tab[:, 2] "Helper array with only useful side temperature values"; final parameter Real scaTAmbSidToPoi[size(scaTAmbSid, 1)]( each min=-100, each max=100) = (scaTAmbSid - fill(TAmbSidMin, size(scaTAmbSid, 1)))*(icoMax - icoMin)/(TAmbSidMax - TAmbSidMin) + fill(icoMin, size(scaTAmbSid, 1)) "Scale ambient side to icon size"; final parameter Real scaTUseSidToPoi[size(scaTAmbSid, 1)]( each min=-100, each max=100) = (scaTUseSid - fill(TUseSidMin, size(scaTUseSid, 1)))*(icoMax - icoMin)/(TUseSidMax - TUseSidMin) + fill(icoMin, size(scaTUseSid, 1)) "Scale useful side to icon size"; equation connect(nor.y, noErr); connect(hysLef.y, nor.u[1]); connect(hysRig.y, nor.u[2]); connect(subMax.u2,conTAmbSidMax.y); connect(sub.u2,conTAmbSidMin.y); connect(subMax.y, hysRig.u); connect(sub.y, hysLef.u); connect(hysBou.u, subBou.y); connect(hysBou.y, nor.u[3]); connect(tabBou.y[1], subBou.u2); connect(subBou.u1, TUseSid); connect(TAmbSid, tabBou.u); connect(TAmbSid, sub.u1); connect(TAmbSid, subMax.u1); end BoundaryMap;

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.CycleRateBoundary

Checks if the cycle rate is in boundary

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.CycleRateBoundary

Information

The block counts the number of times the device is turned on in a given time interval by tracking the rising edge of the boolean input signal. If this number is higher than a set value, the block indicates an error.

Extends from Modelica.Blocks.Interfaces.BooleanSISO (Single Input Single Output control block with signals of type Boolean).

Parameters

Type	Name	Default	Description
Integer	maxCycRat		Maximal cycle rate
Time	delTim	3600	Delay time of output with respect to input signal [s]

Connectors

Type	Name	Description
input BooleanInput	u	Connector of Boolean input signal
output BooleanOutput	y	Connector of Boolean output signal

Modelica definition

block CycleRateBoundary "Checks if the cycle rate is in boundary" extends Modelica.Blocks.Interfaces.BooleanSISO; parameter Integer maxCycRat "Maximal cycle rate"; parameter Modelica.Units.SI.Time delTim(displayUnit="h") = 3600 "Delay time of output with respect to input signal"; Modelica.Blocks.Logical.LessThreshold runCouLesMax(threshold=maxCycRat) "Checks if the count of total runs is lower than the maximal value"; Modelica.Blocks.MathInteger.TriggeredAdd triAdd "Count number of starts"; Modelica.Blocks.Sources.IntegerConstant intConPluOne(final k=1) "Value for counting"; Modelica.Blocks.Math.IntegerToReal intToRea "Convert to real in order to compare and delay"; Modelica.Blocks.Math.Add sub(k2=-1) "Difference of current and delayed starts"; Modelica.Blocks.Nonlinear.FixedDelay fixDel(final delayTime=delTim) "Apply delay to enable starts per delay time"; equation connect(intConPluOne.y, triAdd.u); connect(intToRea.u, triAdd.y); connect(intToRea.y, sub.u1); connect(intToRea.y, fixDel.u); connect(fixDel.y, sub.u2); connect(runCouLesMax.y, y); connect(u, triAdd.trigger); connect(sub.y, runCouLesMax.u); end CycleRateBoundary;

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.OnOffFuzzyLogic

Fuzzy logic approach for on-off control

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.OnOffFuzzyLogic

Information

The model uses a fuzzy logic approach to avoid the need for a state-machine. The device either has to turn off, run at the desired operating speed, or run at the minimal speed.

Parameters

Type	Name	Default	Description
Real	ySetRed		Reduced relative compressor speed to allow longer on-time

Connectors

Type	Name	Description
input BooleanInput	turOn	Indicates if device should turn on
input BooleanInput	isAblToTurOn	Indicates if the device can turn on
input BooleanInput	turOff	Indicates if the device should turn off
input BooleanInput	isAblToTurOff	Indicates if the device can turn off
input BooleanInput	staOff	Indicates if the device has to stay off
input BooleanInput	staOn	Indicates if the device has to stay on
output RealOutput	yOut	Output for relative compressor speed from 0 to 1
input RealInput	ySet	Input for relative compressor speed from 0 to 1

Modelica definition

model OnOffFuzzyLogic "Fuzzy logic approach for on-off control" parameter Real ySetRed "Reduced relative compressor speed to allow longer on-time"; Modelica.Blocks.Interfaces.BooleanInput turOn(start=false, fixed=true) "Indicates if device should turn on"; Modelica.Blocks.Interfaces.BooleanInput isAblToTurOn "Indicates if the device can turn on"; Modelica.Blocks.Interfaces.BooleanInput turOff(start=false, fixed=true) "Indicates if the device should turn off"; Modelica.Blocks.Interfaces.BooleanInput isAblToTurOff "Indicates if the device can turn off"; Modelica.Blocks.Interfaces.BooleanInput staOff "Indicates if the device has to stay off"; Modelica.Blocks.Interfaces.BooleanInput staOn "Indicates if the device has to stay on"; Modelica.Blocks.Interfaces.RealOutput yOut "Output for relative compressor speed from 0 to 1"; Modelica.Blocks.Interfaces.RealInput ySet "Input for relative compressor speed from 0 to 1"; protected Integer devRunMin(start=0, fixed=true) "Indicates if device needs to run at minimal limit"; Integer devTurOff(start=0, fixed=true) "Indicates if device needs to turn off"; Integer devNorOpe(start=1, fixed=true) "Indicates if device is at normal operation"; equation // The part "+ 0 * devTurOff" is implicitly included yOut = ySet * devNorOpe + ySetRed * devRunMin; when edge(turOn) then if isAblToTurOn then devTurOff = 0; devRunMin = 0; devNorOpe = 1; else devTurOff = 1; devRunMin = 0; devNorOpe = 0; end if; elsewhen edge(turOff) then if isAblToTurOff then devTurOff = 0; devRunMin = 0; devNorOpe = 1; else devTurOff = 0; devRunMin = 1; devNorOpe = 0; end if; elsewhen isAblToTurOn and turOn then devTurOff = 0; devRunMin = 0; devNorOpe = 1; elsewhen isAblToTurOff and turOff then devTurOff = 0; devRunMin = 0; devNorOpe = 1; elsewhen staOff then devTurOff = 0; devRunMin = 0; devNorOpe = 1; elsewhen staOn then devTurOff = 0; devRunMin = 0; devNorOpe = 1; end when; end OnOffFuzzyLogic;

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.OnPastThreshold

Returns true if the device stays on for longer than a threshold time

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.OnPastThreshold

Information

This block delays a true signal and only returns true if the device stays on (true) for longer than a threshold time. If the device is switched off before the threshold time, this block continues returning false.

This block is used to check the mimimal on- or off-time of a device.

Extends from Modelica.Blocks.Interfaces.BooleanSISO (Single Input Single Output control block with signals of type Boolean).

Parameters

Type	Name	Default	Description
Time	minOnTime		Minimal time the device is turned on or off [s]

Connectors

Type	Name	Description
input BooleanInput	u	Connector of Boolean input signal
output BooleanOutput	y	Connector of Boolean output signal

Modelica definition

block OnPastThreshold "Returns true if the device stays on for longer than a threshold time" extends Modelica.Blocks.Interfaces.BooleanSISO; parameter Modelica.Units.SI.Time minOnTime "Minimal time the device is turned on or off"; Modelica.Blocks.Logical.Timer runTim "Counts the seconds the heat pump is locked still"; Modelica.Blocks.Logical.GreaterEqualThreshold runTimGreMin(final threshold= minOnTime) "Checks if the on-time is greater than the minimal on-time"; equation connect(runTimGreMin.y, y); connect(u,runTim. u); connect(runTim.y, runTimGreMin.u); end OnPastThreshold;

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.PartialOperationalEnvelope

Indicates if the device operation is within a defined envelope

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.PartialOperationalEnvelope

Information

Model to check if the operating conditions are inside the given boundaries. If not, the heat pump or chiller will switch off.

This safety control is mainly based on the operational envelope of the compressor. Refrigerant flowsheet and type will influence these values.

Limitations

Only three sides of the real envelope are implemented (Figures 2 and 3). The real operational envelope implies continuous operation. This means start-up from e.g. a cold heat pump supply temperature is possible. To avoid additional equations for startup and continuous operation, we neither implement the lower boundary for heating nor the upper boundary for cooling devices. This avoids the situation where the device can never be turned on.
From all the influences on the real envelope, the compressor frequency impacts the possible range of operation. However, the compressor speed-dependent envelopes are typcially not provided in datasheets. Further, including a third dimension requires 3D-table data. This is currently not supported by Buildings or Modelica Standard Library.

Existing envelopes

Technical datasheets often contain information about the operational envelope. The device records for heat pumps ( Buildings.Fluid.HeatPumps.ModularReversible.RefrigerantCycle.TableData2DData) and chillers ( Buildings.Fluid.Chillers.ModularReversible.RefrigerantCycle.TableData2DData) contain typical values. Older devices typically have lower limits while new refrigerant machines based on propane or advanced flowsheets are able to achieve temperature over 70 °C for heating.

Parameterization from datasheets

Depending on the underlying datasheet in use, you have to think thoroughly if you need inlet or outlet conditions, and if you are modelling a heat pump or chiller. Figure 1 depicts possible upper and lower boundaries as well as what variables the boundaries are defined with. Depending on your setup, you may have to transpose existing boundaries. For instance, when using an envelope designed for a heat pump in a chiller model, the useful side (column 2 of the data) is not the condenser but the evaporator. Thus, you have to switch columns 1 and 2. The following examples aim to explain how to obtain the envelopes:

If the model in use is a heat pump, the useful side is always the side of TConOutMea and TConInMea. In the chiller, the useful side is always the side of TEvaOutMea or TEvaInMea.

The envelopes for air-to-water heat pumps often contain water supply temperature (TConOutMea) on the y-axis and ambient temperatures (TEvaInMea) on the x-axis. In these cases, tabUppHea is based on the y-axis maximal values and tabLowCoo based on the y-axis minimal values. Figure 2 depicts this setup.
The envelopes for air-to-air devices often contain ambient inlet (TConInMea) as y and room (TEvaInMea) inlet temperatures as x. In these cases, tabUppHea is based on the x-axis maximal values and tabLowCoo based on the x-axis minimal values. Figure 3 depicts this setup.
Compressor datasheets often provide evaporating and condensing temperatures or pressure levels. Those are not avaiable in the simpified model approach. Thus, you have to assume pinch temperatures to convert it to either in- or outflow temperature levels of the secondary side temperatures (i.e. TConOutMea, TConInMea, TEvaInMea, TEvaOutMea).

Figure 1: Possible upper and lower boundaries as well as temperature specifications in datasheets

Figure 2: Example for an air-to-water heat pump or chiller. The supply temperature is the temperature leaving the device into the hydraulic circuit of the building. Red crosses indicate the point to write into the 2D table in Modelica.

Figure 3: Example for an air-to-air heat pump or chiller. The room temperature acts as an inflow to the device. Red crosses indicate the point to write into the 2D table in Modelica.

Extends from BaseClasses.PartialSafetyWithCounter (Safety control which adds an error counter to the I/O).

Parameters

Type	Name	Default	Description
Temperature	tabUppHea[:, 2]		Upper boundary for heating with second column as useful temperature side [K]
Temperature	tabLowCoo[:, 2]		Lower boundary for cooling with second column as useful temperature side [K]
TemperatureDifference	dTHys	5	Temperature deadband in the operational envelope [K]
Operational Envelope
Boolean	use_TConOutHea	true	=true to use condenser outlet temperature for envelope in heating mode, false for inlet
Boolean	use_TEvaOutHea	false	=true to use evaporator outlet temperature for envelope in heating mode, false for inlet
Boolean	use_TConOutCoo	false	=true to use useful side outlet temperature for envelope in cooling mode, false for inlet
Boolean	use_TEvaOutCoo	true	=true to use evaporator outlet temperature for envelope in cooling mode, false for inlet

Connectors

Type	Name	Description
input RealInput	ySet	Input for relative compressor speed from 0 to 1
output RealOutput	yOut	Output for relative compressor speed from 0 to 1
RefrigerantMachineControlBus	sigBus	Bus-connector for the heat pump
output IntegerOutput	err	Integer for displaying number of errors during simulation

Modelica definition

partial model PartialOperationalEnvelope "Indicates if the device operation is within a defined envelope" extends BaseClasses.PartialSafetyWithCounter; parameter Modelica.Units.SI.Temperature tabUppHea[:,2] "Upper boundary for heating with second column as useful temperature side"; parameter Modelica.Units.SI.Temperature tabLowCoo[:,2] "Lower boundary for cooling with second column as useful temperature side"; parameter Boolean use_TConOutHea=true "=true to use condenser outlet temperature for envelope in heating mode, false for inlet"; parameter Boolean use_TEvaOutHea=false "=true to use evaporator outlet temperature for envelope in heating mode, false for inlet"; parameter Boolean use_TConOutCoo=false "=true to use useful side outlet temperature for envelope in cooling mode, false for inlet"; parameter Boolean use_TEvaOutCoo=true "=true to use evaporator outlet temperature for envelope in cooling mode, false for inlet"; parameter Modelica.Units.SI.TemperatureDifference dTHys=5 "Temperature deadband in the operational envelope"; Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.BoundaryMap bouMapHea( final tab=tabUppHea, final dT=dTHys, final isUppBou=true) "Operational boundary map for heating operation"; Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.BoundaryMap bouMapCoo( final tab=tabLowCoo, final dT=dTHys, final isUppBou=false) "Operational boundary map for cooling operation"; Modelica.Blocks.Logical.LogicalSwitch swiHeaCoo "Switch between heating and cooling envelope"; equation connect(ySet,swiErr.u1); connect(swiHeaCoo.y, booPasThr.u); connect(bouMapCoo.noErr, swiHeaCoo.u3); connect(bouMapHea.noErr, swiHeaCoo.u1); end PartialOperationalEnvelope;

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.PartialSafety

Safety control with I/O

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.PartialSafety

Information

Partial block for a safety control. Based on the signals in the sigBus either the input signals are equal to the output signals or, if an error occurs, set to 0.

Connectors

Type	Name	Description
input RealInput	ySet	Input for relative compressor speed from 0 to 1
output RealOutput	yOut	Output for relative compressor speed from 0 to 1
RefrigerantMachineControlBus	sigBus	Bus-connector for the heat pump

Modelica definition

partial model PartialSafety "Safety control with I/O" Modelica.Blocks.Interfaces.RealInput ySet "Input for relative compressor speed from 0 to 1"; Modelica.Blocks.Interfaces.RealOutput yOut "Output for relative compressor speed from 0 to 1"; Buildings.Fluid.HeatPumps.ModularReversible.BaseClasses.RefrigerantMachineControlBus sigBus "Bus-connector for the heat pump"; end PartialSafety;

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.PartialSafetyWithCounter

Safety control which adds an error counter to the I/O

Buildings.Fluid.HeatPumps.ModularReversible.Controls.Safety.BaseClasses.PartialSafetyWithCounter

Information

This block counts the number of errors occurred in a specific safety block.

Extends from PartialSafety (Safety control with I/O).

Connectors

Type	Name	Description
input RealInput	ySet	Input for relative compressor speed from 0 to 1
output RealOutput	yOut	Output for relative compressor speed from 0 to 1
RefrigerantMachineControlBus	sigBus	Bus-connector for the heat pump
output IntegerOutput	err	Integer for displaying number of errors during simulation

Modelica definition

partial model PartialSafetyWithCounter "Safety control which adds an error counter to the I/O" extends PartialSafety; Modelica.Blocks.Logical.Switch swiErr "Switches to zero when an error occurs"; Modelica.Blocks.Sources.Constant conZer(final k=0) "Constant zero"; Modelica.Blocks.MathInteger.TriggeredAdd disErr( y_start=0, use_reset=false, use_set=false) "Used to show if the error was triggered"; Modelica.Blocks.Interfaces.IntegerOutput err "Integer for displaying number of errors during simulation"; Modelica.Blocks.Logical.Not notVal "=true indicates a error"; Modelica.Blocks.Sources.IntegerConstant intConOne(final k=1) "Used for display of current error"; Modelica.Blocks.Routing.BooleanPassThrough booPasThr "Used to keep the connection to the counter"; equation connect(conZer.y,swiErr. u3); connect(disErr.y,err); connect(notVal.y, disErr.trigger); connect(intConOne.y, disErr.u); connect(booPasThr.y, swiErr.u2); connect(booPasThr.y, notVal.u); connect(swiErr.y, yOut); end PartialSafetyWithCounter;