Buildings.Examples.ChillerPlant.BaseClasses.Controls
Package with control components for Buildings.Examples.ChillerPlant
Information
This package contains component models that are used to construct the control system in Buildings.Examples.ChillerPlant.
Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).
Package Content
| Name | Description |
|---|---|
 BatteryControl
|
Controller for battery |
 ChillerSwitch
|
Control unit for enabling/disabling chiller |
 KMinusU
|
Output y=k-u |
 LinearPiecewiseTwo
|
A two-pieces linear piecewise function |
 RequestCounter
|
Count the number of actuators that have request |
 TrimAndRespond
|
Trim and respond logic |
 TrimAndRespondContinuousTimeApproximation
|
Trim and respond logic |
 WSEControl
|
Control unit for WSE |
 Examples
|
Test of components |
Buildings.Examples.ChillerPlant.BaseClasses.Controls.BatteryControl
Controller for battery
Information
Block for a battery controller. The battery is charged during night if its charge is below a threshold. It remains charging until it is full. During day, it discharges provided that its charge is above a threshold. It remains discharging until it is empty.
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | SOC | State of charge |
| output RealOutput | y | Power charged or discharged from battery |
Modelica definition
model BatteryControl "Controller for battery"
Modelica.Blocks.Interfaces.RealInput SOC "State of charge";
Modelica.Blocks.Interfaces.RealOutput y
"Power charged or discharged from battery";
Modelica.Blocks.Logical.LessThreshold lessThreshold(threshold=0.5);
Modelica.Blocks.Logical.GreaterEqualThreshold greaterEqualThreshold(threshold=
0.99);
Modelica.Blocks.Sources.BooleanExpression isDay(y=mod(time, 86400) > 7*3600
and mod(time, 86400) <= 19*3600) "Outputs true if it is day time";
Modelica.Blocks.Logical.Not not1;
Modelica.Blocks.Logical.And and1;
Modelica.Blocks.Logical.And and2;
Modelica.Blocks.Logical.GreaterThreshold greaterThreshold(threshold=0.8);
Modelica.Blocks.Logical.LessEqualThreshold lessEqualThreshold(threshold=
0.01);
Modelica.Blocks.Math.MultiSwitch multiSwitch1(
nu=2,
expr={200e3,-400e3});
Modelica.StateGraph.InitialStep off "Off state";
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot;
Modelica.StateGraph.Alternative alternative(nBranches=2)
"Splitter for alternative branches";
Modelica.StateGraph.TransitionWithSignal t1(enableTimer=true, waitTime=1)
"Transition to charge";
Modelica.StateGraph.TransitionWithSignal t2(enableTimer=true, waitTime=1)
"Transition to discharge";
Modelica.StateGraph.StepWithSignal charge "Charge battery";
Modelica.StateGraph.StepWithSignal discharge "Discharge battery";
Modelica.StateGraph.TransitionWithSignal t3 "Transition to off";
Modelica.StateGraph.TransitionWithSignal t4 "Transition to off";
equation
connect(lessThreshold.u, SOC);
connect(greaterEqualThreshold.u, SOC);
connect(not1.u, isDay.y);
connect(and1.u1, not1.y);
connect(lessThreshold.y, and1.u2);
connect(isDay.y, and2.u1);
connect(greaterThreshold.u, SOC);
connect(greaterThreshold.y, and2.u2);
connect(lessEqualThreshold.u, SOC);
connect(multiSwitch1.y, y);
connect(off.outPort[1], alternative.inPort);
connect(t1.outPort, charge.inPort[1]);
connect(t2.outPort, discharge.inPort[1]);
connect(charge.outPort[1], t3.inPort);
connect(discharge.outPort[1], t4.inPort);
connect(alternative.outPort, off.inPort[1]);
connect(and1.y, t1.condition);
connect(and2.y, t2.condition);
connect(greaterEqualThreshold.y, t3.condition);
connect(lessEqualThreshold.y, t4.condition);
connect(t1.inPort, alternative.split[1]);
connect(t2.inPort, alternative.split[2]);
connect(t3.outPort, alternative.join[1]);
connect(t4.outPort, alternative.join[2]);
connect(charge.active, multiSwitch1.u[1]);
connect(discharge.active, multiSwitch1.u[2]);
end BatteryControl;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.ChillerSwitch
Control unit for enabling/disabling chiller
Information
The controls for enabling/disabling chiller are as follows:-
The chiller is enabled when
TChi_CHWST > TChiSet + TDeaBan
-
The chiller is disabled when
TChi_CHWST ≤ TChiSet
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Temperature | deaBan | Dead band of temperature to prevent chiller short cycling [K] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | chiCHWST | Chiller chilled water supply temperature (water entering chiller) [K] |
| output BooleanOutput | y | Control signal for chiller. 1: Enable, 0: Disable |
| input RealInput | TSet | Set temperature of chiller [K] |
Modelica definition
block ChillerSwitch "Control unit for enabling/disabling chiller"
extends Modelica.Blocks.Icons.Block;
Modelica.Blocks.Interfaces.RealInput chiCHWST(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="deg")
"Chiller chilled water supply temperature (water entering chiller)";
Modelica.Blocks.Interfaces.BooleanOutput y
"Control signal for chiller. 1: Enable, 0: Disable";
Modelica.Blocks.Interfaces.RealInput TSet(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="deg") "Set temperature of chiller";
parameter Modelica.SIunits.Temperature deaBan
"Dead band of temperature to prevent chiller short cycling";
Modelica.Blocks.Logical.Hysteresis hysteresis(uLow=0, uHigh=deaBan);
Modelica.Blocks.Math.Add add(k1=+1, k2=-1);
equation
connect(hysteresis.y, y);
connect(chiCHWST, add.u1);
connect(TSet, add.u2);
connect(add.y, hysteresis.u);
end ChillerSwitch;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.KMinusU
Output y=k-u
Information
This component computes the value ofy = k - u.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | k | Sum of u and y |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Input |
| output RealOutput | y | Output |
Modelica definition
block KMinusU "Output y=k-u"
extends Modelica.Blocks.Icons.Block;
public
parameter Real k "Sum of u and y";
Modelica.Blocks.Interfaces.RealInput u "Input";
Modelica.Blocks.Interfaces.RealOutput y "Output";
equation
y = k - u;
end KMinusU;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.LinearPiecewiseTwo
A two-pieces linear piecewise function
Information
This component calcuates the output according to two piecewise linear function as
| u ∈ [x0, x1]: | y1 = y10 + u (y11-y10)/(x1-x0) y2 = y20 |
| u ∈ (x1, x2]: | y1 = y11 y2 = y20 + (u-x1) (y21-y20)/(x2-x1) |
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | x0 | First interval [x0, x1] | |
| Real | x1 | First interval [x0, x1] and second interval (x1, x2] | |
| Real | x2 | Second interval (x1, x2] | |
| Real | y10 | y[1] at u = x0 | |
| Real | y11 | y[1] at u = x1 | |
| Real | y20 | y[2] at u = x1 | |
| Real | y21 | y[2] at u = x2 |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Set point |
| output RealOutput | y[2] | Connectors of Real output signal |
Modelica definition
block LinearPiecewiseTwo "A two-pieces linear piecewise function"
extends Modelica.Blocks.Icons.Block;
parameter Real x0 "First interval [x0, x1]";
parameter Real x1 "First interval [x0, x1] and second interval (x1, x2]";
parameter Real x2 "Second interval (x1, x2]";
parameter Real y10 "y[1] at u = x0";
parameter Real y11 "y[1] at u = x1";
parameter Real y20 "y[2] at u = x1";
parameter Real y21 "y[2] at u = x2";
Modelica.Blocks.Interfaces.RealInput u "Set point";
Modelica.Blocks.Interfaces.RealOutput y[2] "Connectors of Real output signal";
Buildings.Controls.SetPoints.Table y1Tab(table=[x0, y10; x1, y11; x2, y11])
"Table for y[1]";
Buildings.Controls.SetPoints.Table y2Tab(table=[x0, y20; x1, y20; x2, y21])
"Table for y[2]";
equation
connect(u, y1Tab.u);
connect(u, y2Tab.u);
connect(y1Tab.y, y[1]);
connect(y2Tab.y, y[2]);
end LinearPiecewiseTwo;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.RequestCounter
Count the number of actuators that have request
Information
This model counts the number of requests sent by actuators. A request is triggerred when an input singaluAct[i] is larger than uTri.
Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nAct | Number of actuators | |
| Real | uTri | Value to trigger a request from actuator |
Connectors
| Type | Name | Description |
|---|---|---|
| output IntegerOutput | nInc | Number of actuators requesting control signal increase |
| input RealInput | uAct[nAct] | Input signal from actuators |
Modelica definition
block RequestCounter "Count the number of actuators that have request"
extends Modelica.Blocks.Icons.Block;
parameter Integer nAct "Number of actuators";
parameter Real uTri "Value to trigger a request from actuator";
Modelica.Blocks.Interfaces.IntegerOutput nInc
"Number of actuators requesting control signal increase";
Modelica.Blocks.Interfaces.RealInput uAct[nAct] "Input signal from actuators";
algorithm
nInc := 0;
for i in 1:nAct loop
if uAct[i] > uTri then
nInc := nInc + 1;
end if;
end for;
end RequestCounter;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.TrimAndRespond
Trim and respond logic
Information
This model implements the trim and respond logic. The model samples the outputs of actuators every tSam.
The control sequence is as follows:
- If
u ≥ 0, theny = y + nActInc, - If
u < 0, theny = y - yDec.
Extends from Modelica.Blocks.Interfaces.DiscreteSISO (Single Input Single Output discrete control block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | samplePeriod | Sample period of component [s] | |
| Time | startTime | 0 | First sample time instant [s] |
| Real | uTri | Value to triggering the request for actuator | |
| Real | yEqu0 | y setpoint when equipment starts | |
| Real | yDec | y decrement (must be negative) | |
| Real | yInc | y increment (must be positive) |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| output RealOutput | y | Continuous output signal |
Modelica definition
block TrimAndRespond "Trim and respond logic"
extends Modelica.Blocks.Interfaces.DiscreteSISO(firstTrigger(start=false, fixed=true));
parameter Real uTri "Value to triggering the request for actuator";
parameter Real yEqu0 "y setpoint when equipment starts";
parameter Real yDec(max=0) "y decrement (must be negative)";
parameter Real yInc(min=0) "y increment (must be positive)";
Modelica.Blocks.Logical.GreaterEqualThreshold incY(threshold=0)
"Outputs true if y needs to be increased";
Modelica.Blocks.Logical.Switch swi;
Sampler sam(samplePeriod=samplePeriod) "Sampler";
Modelica.Blocks.Sources.Constant conYDec(k=yDec) "y decrease";
Modelica.Blocks.Sources.Constant conYInc(k=yInc) "y increase";
UnitDelay uniDel1(
y_start=yEqu0,
samplePeriod=samplePeriod,
startTime=samplePeriod);
Modelica.Blocks.Math.Add add;
Modelica.Blocks.Nonlinear.Limiter lim(uMax=1, uMin=0) "State limiter";
// The UnitDelay and Sampler is reimplemented to avoid in Dymola 2016 the translation warning
// The initial conditions for variables of type Boolean are not fully specified.
// Dymola has selected default initial conditions.
// Assuming fixed default start value for the discrete non-states:
// ...firstTrigger(start = false)
// ...
protected
block UnitDelay
extends Modelica.Blocks.Discrete.UnitDelay(
firstTrigger(start=false, fixed=true));
end UnitDelay;
block Sampler
extends Modelica.Blocks.Discrete.Sampler(
firstTrigger(start=false, fixed=true));
end Sampler;
equation
connect(lim.y, y);
connect(add.y, lim.u);
connect(uniDel1.y, add.u2);
connect(incY.y, swi.u2);
connect(sam.y, incY.u);
connect(lim.y, uniDel1.u);
connect(swi.y, add.u1);
connect(swi.u3, conYDec.y);
connect(conYInc.y, swi.u1);
connect(sam.u, u);
end TrimAndRespond;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.TrimAndRespondContinuousTimeApproximation
Trim and respond logic
Information
This model implements a continuous time approximation to the trim and respond control algorithm.
Extends from Modelica.Blocks.Interfaces.SISO (Single Input Single Output continuous control block).
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Connector of Real input signal |
| output RealOutput | y | Connector of Real output signal |
Modelica definition
block TrimAndRespondContinuousTimeApproximation "Trim and respond logic"
extends Modelica.Blocks.Interfaces.SISO;
Buildings.Controls.Continuous.LimPID conPID(
Td=1,
yMax=1,
yMin=0,
reverseAction=true,
controllerType=Modelica.Blocks.Types.SimpleController.PI,
Ti=120,
k=0.1);
Modelica.Blocks.Sources.Constant const(k=0);
equation
connect(const.y, conPID.u_s);
connect(conPID.y, y);
connect(u, conPID.u_m);
end TrimAndRespondContinuousTimeApproximation;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.WSEControl
Control unit for WSE
Information
This component decides if the WSE is set to on or off. The WSE is enabled when
- The WSE has been disabled for at least 20 minutes, and
- TWSE_CHWST > 0.9 TWetBul + TTowApp + TWSEApp
The WSE is disabled when
- The WSE has been enabled for at least 20 minutes, and
- TWSE_CHWRT < 1 + TWSE_CWST
where TWSE_CHWST is the chilled water supply temperature for the WSE, TWetBul is the wet bulb temperature, TTowApp is the cooling tower approach, TWSEApp is the approach for the WSE, TWSE_CHWRT is the chilled water return temperature for the WSE, and TWSE_CWST is the condenser water return temperature for the WSE.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| TemperatureDifference | dTOff | 1 | Temperature difference to switch WSE off [K] |
| TemperatureDifference | dTW | 1 | Temperature difference that is added to WSE on guard [K] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | wseCHWST | WSE chilled water supply temperature (water entering WSE) [K] |
| output RealOutput | y2 | Control signal for chiller shutoff valve |
| input RealInput | TWetBul | Wet bulb temperature [K] |
| input RealInput | towTApp | Cooling tower approach [K] |
| input RealInput | wseCWST | WSE condenser water supply temperature (water entering WSE) [K] |
| output RealOutput | y1 | Control signal for WSE shutoff valve |
Modelica definition
model WSEControl "Control unit for WSE"
parameter Modelica.SIunits.TemperatureDifference dTOff = 1
"Temperature difference to switch WSE off";
parameter Modelica.SIunits.TemperatureDifference dTW = 1
"Temperature difference that is added to WSE on guard";
Modelica.Blocks.Interfaces.RealInput wseCHWST(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="deg")
"WSE chilled water supply temperature (water entering WSE)";
Modelica.Blocks.Interfaces.RealOutput y2
"Control signal for chiller shutoff valve";
Modelica.Blocks.Interfaces.RealInput TWetBul(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="deg") "Wet bulb temperature";
Modelica.Blocks.Interfaces.RealInput towTApp(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="deg") "Cooling tower approach";
Modelica.Blocks.Interfaces.RealInput wseCWST(
final quantity="ThermodynamicTemperature",
final unit="K",
displayUnit="deg")
"WSE condenser water supply temperature (water entering WSE)";
Modelica.Blocks.Math.BooleanToReal booToRea2;
Modelica.Blocks.Interfaces.RealOutput y1
"Control signal for WSE shutoff valve";
Modelica.StateGraph.InitialStepWithSignal off(
nOut=1,
nIn=1);
Modelica.StateGraph.Transition T1( waitTime=1200,
condition=wseCHWST > 0.9*TWetBul + towTApp + dTW,
enableTimer=true);
Modelica.StateGraph.Step on(nIn=1, nOut=1);
Modelica.StateGraph.Transition T2( waitTime=1200,
condition=wseCHWST < wseCWST + dTOff,
enableTimer=true);
Modelica.Blocks.Math.BooleanToReal booToRea1(realTrue=0, realFalse=1);
inner Modelica.StateGraph.StateGraphRoot stateGraphRoot
"Root of the state graph";
equation
connect(booToRea2.y, y2);
connect(off.outPort[1], T1.inPort);
connect(T1.outPort, on.inPort[1]);
connect(on.outPort[1], T2.inPort);
connect(T2.outPort, off.inPort[1]);
connect(booToRea1.y, y1);
connect(off.active, booToRea1.u);
connect(off.active, booToRea2.u);
end WSEControl;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.TrimAndRespond.Sampler
Information
Extends from Modelica.Blocks.Discrete.Sampler (Ideal sampling of continuous signals).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | samplePeriod | Sample period of component [s] | |
| Time | startTime | 0 | First sample time instant [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| output RealOutput | y | Continuous output signal |
Modelica definition
block Sampler
extends Modelica.Blocks.Discrete.Sampler(
firstTrigger(start=false, fixed=true));
end Sampler;
Buildings.Examples.ChillerPlant.BaseClasses.Controls.TrimAndRespond.UnitDelay
Information
Extends from Modelica.Blocks.Discrete.UnitDelay (Unit Delay Block).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | y_start | 0 | Initial value of output signal |
| Time | samplePeriod | Sample period of component [s] | |
| Time | startTime | 0 | First sample time instant [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| output RealOutput | y | Continuous output signal |
Modelica definition
block UnitDelay
extends Modelica.Blocks.Discrete.UnitDelay(
firstTrigger(start=false, fixed=true));
end UnitDelay;