Buildings.Examples.ChillerPlant.BaseClasses.Controls

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
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
WSEControl	Control unit for WSE
ZeroOrderHold	Zero order hold for boolean variable
Examples	Test of components

Buildings.Examples.ChillerPlant.BaseClasses.Controls.ChillerSwitch

Information

• The chiller is enabled when TChi_CHWST > TChiSet + TDeaBan
• The chiller is disabled when TChi_CHWST ≤ TChiSet

Extends from Modelica.Blocks.Interfaces.BlockIcon (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.Interfaces.BlockIcon;
  Modelica.Blocks.Interfaces.RealInput chiCHWST(
    final quantity="Temperature",
    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="Temperature",
    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

Information

y = k - u.

Extends from Modelica.Blocks.Interfaces.BlockIcon (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.Interfaces.BlockIcon;
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

Information

This component calcuates the output according to two piecewise linear function as

Extends from Modelica.Blocks.Interfaces.BlockIcon (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.Interfaces.BlockIcon;
  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]) 
    "Tabel for y[1]";
  Buildings.Controls.SetPoints.Table y2Tab(table=[x0, y20; x1, y20; x2, y21]) 
    "Tabel 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

Information

Extends from Modelica.Blocks.Interfaces.BlockIcon (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.Interfaces.BlockIcon;
  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

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 sta = false, then y = yEqu0.
• If sta = true, then,
  • If nReq > nActInc, then y = y + nActInc,
  • If nReq < nActDec, then y = y - yDec,
  • else y = y.

Extends from Modelica.Blocks.Interfaces.DiscreteBlockIcon (Graphical layout of discrete block component icon).

Parameters

Type	Name	Default	Description
Integer	n		Number of input singals
Real	uTri		Value to triggering the request for actuator
Real	yEqu0		y setpoint when equipment starts
Real	yMax		Upper limit for y
Real	yMin		Lower limit for y
Real	yDec		y decrement (must be negative)
Real	yInc		y increment (must be positive)
Integer	nActDec		Number of actuators that can violate setpoints and y is still decreased
Integer	nActInc		Number of actuators requests needed to increase y
Time	tSam		Sample period of component [s]

Connectors

Type	Name	Description
input RealInput	u[n]	Input singal
output RealOutput	y	Connector of Real output signal
input BooleanInput	sta	Status indicator, true if equipment is on

Modelica definition

block TrimAndRespond "Trim and respond logic"
  extends Modelica.Blocks.Interfaces.DiscreteBlockIcon;
  parameter Integer n "Number of input singals";
  parameter Real uTri "Value to triggering the request for actuator";
  parameter Real yEqu0 "y setpoint when equipment starts";
  parameter Real yMax "Upper limit for y";
  parameter Real yMin "Lower limit for y";
  parameter Real yDec "y decrement (must be negative)";
  parameter Real yInc "y increment (must be positive)";
  parameter Integer nActDec 
    "Number of actuators that can violate setpoints and y is still decreased";
  parameter Integer nActInc "Number of actuators requests needed to increase y";
  Modelica.Blocks.Interfaces.RealInput u[n] "Input singal";
  Modelica.Blocks.Logical.GreaterThreshold incY(threshold=nActInc - 0.5) 
    "Outputs true if y needs to be increased";
  Modelica.Blocks.Logical.Switch swi;
  Modelica.Blocks.Discrete.Sampler sam(samplePeriod=tSam) "Sampler";
  parameter Modelica.SIunits.Time tSam "Sample period of component";
  Modelica.Blocks.Sources.Constant conYDec(k=yDec) "y decrease";
  Modelica.Blocks.Math.IntegerToReal intToRea "Convert Integer to Real";
  Modelica.Blocks.Sources.Constant conYInc(k=yInc) "y increase";
  Modelica.Blocks.Discrete.UnitDelay uniDel1(
    samplePeriod=tSam,
    startTime=tSam,
    y_start=yEqu0);
  Modelica.Blocks.Math.Add add;
  Modelica.Blocks.Nonlinear.Limiter lim(uMax=yMax, uMin=yMin) "State limiter";
  Modelica.Blocks.Logical.Switch onSetPoi 
    "Set point selecter when equipment switches on";
  Modelica.Blocks.Sources.Constant equSta(k=yEqu0) "equipment start signal";
  Modelica.Blocks.Interfaces.RealOutput y "Connector of Real output signal";
  Modelica.Blocks.Logical.LessThreshold decY(threshold=nActDec + 0.5) 
    "Outputs true if y needs to be decreased";
  Modelica.Blocks.Logical.Switch swi1;
  Modelica.Blocks.Sources.Constant zer1(k=0) "Set point when equipment is off";
  Modelica.Blocks.Interfaces.BooleanInput sta 
    "Status indicator, true if equipment is on";
  ZeroOrderHold zerOrdHol(samplePeriod=tSam) "Zero order hold";
  Buildings.Examples.ChillerPlant.BaseClasses.Controls.RequestCounter req(uTri=
        uTri, nAct=n) "Count the number of request";
equation 
  connect(incY.y, swi.u2);
  connect(sam.y, incY.u);
  connect(uniDel1.y, add.u2);
  connect(add.y, lim.u);
  connect(onSetPoi.y, y);
  connect(zer1.y, swi1.u3);
  connect(swi1.y, swi.u3);
  connect(onSetPoi.y, uniDel1.u);
  connect(sta, zerOrdHol.u);
  connect(req.nInc, intToRea.u);
  connect(intToRea.y, sam.u);
  connect(conYInc.y, swi.u1);
  connect(sam.y, decY.u);
  connect(decY.y, swi1.u2);
  connect(conYDec.y, swi1.u1);
  connect(u, req.uAct);
  connect(equSta.y, onSetPoi.u3);
  connect(lim.y, onSetPoi.u1);
  connect(onSetPoi.u2, zerOrdHol.y);
  connect(swi.y, add.u1);
end TrimAndRespond;

Buildings.Examples.ChillerPlant.BaseClasses.Controls.WSEControl

Information

This component decides if the WSE is set to on or off. The WSE is enabled when

1. The WSE has been disabled for at least 20 minutes, and
2. T_{WSE_CHWST} > 0.9 T_WetBul + T_TowApp + T_WSEApp

1. The WSE has been enabled for at least 20 minutes, and
2. T_{WSE_CHWRT} < 1 + T_{WSE_CWST}

Connectors

Type	Name	Description
input RealInput	wseCHWST	WSE's chilled water supply temperature (water entering WSE) [K]
output RealOutput	y2	Control signal for valve in CHW loop of WSE
input RealInput	TWetBul	Wet bulb temperature [K]
input RealInput	towTApp	cooling tower approach [K]
input RealInput	wseCWST	WSE's condenser water supply temperature (water entering WSE) [K]
output RealOutput	y1	Control signal for valve in the CW loop of WSE

Modelica definition

block WSEControl "Control unit for WSE"

  Modelica.Blocks.Interfaces.RealInput wseCHWST(
    final quantity="Temperature",
    final unit="K",
    displayUnit="deg") 
    "WSE's chilled water supply temperature (water entering WSE)";
  Modelica.Blocks.Interfaces.RealOutput y2 
    "Control signal for valve in CHW loop of WSE";
  Modelica.Blocks.Sources.Constant TWSEApp(k=1) "Approach for WSE";
  Modelica.Blocks.Math.Sum sum(nin=3);
  Modelica.Blocks.Logical.Greater greater;
  Modelica.Blocks.Logical.And andOpe;
  Buildings.Controls.Continuous.OffTimer offTim;
  Modelica.Blocks.Sources.Constant minDisTim(k=1200) 
    "minium Disabled time for WSE";
  Modelica.Blocks.Logical.Less less;
  Modelica.Blocks.Interfaces.RealInput TWetBul(
    final quantity="Temperature",
    final unit="K",
    displayUnit="deg") "Wet bulb temperature";
  Modelica.Blocks.Interfaces.RealInput towTApp(
    final quantity="Temperature",
    final unit="K",
    displayUnit="deg") "cooling tower approach";
  Modelica.Blocks.Math.Product pro;
  Modelica.Blocks.Sources.Constant cons(k=0.9);
  Modelica.Blocks.Interfaces.RealInput wseCWST(
    final quantity="Temperature",
    final unit="K",
    displayUnit="deg") 
    "WSE's condenser water supply temperature (water entering WSE)";
  Modelica.Blocks.Logical.Greater less1;
  Modelica.Blocks.Sources.Constant cons1(k=1) "cons";
  Modelica.Blocks.Sources.Constant minEnaTim(k=1200) 
    "minium enabled time for heat exchanger";
  Buildings.Controls.Continuous.OffTimer onTim;
  Modelica.Blocks.Logical.Greater less2;
  Modelica.Blocks.Logical.And dis "true for disable";
  Modelica.Blocks.Math.Add add1(k1=+1);
  Modelica.Blocks.Logical.Not not3;
  Modelica.Blocks.Logical.And and2;
  Modelica.Blocks.Math.BooleanToReal booToRea;
  Modelica.Blocks.Logical.Not not1;
  Modelica.Blocks.Interfaces.RealOutput y1 
    "Control signal for valve in the CW loop of WSE";
  KMinusU kMinU(k=1);
  Modelica.Blocks.Logical.Pre pre1;
equation 
  connect(sum.y, greater.u2);
  connect(greater.y, andOpe.u1);
  connect(minDisTim.y, less.u1);
  connect(offTim.y, less.u2);
  connect(less.y, andOpe.u2);
  connect(TWSEApp.y, sum.u[1]);
  connect(pro.y, sum.u[2]);
  connect(cons.y, pro.u1);
  connect(cons1.y, add1.u1);
  connect(less1.y, dis.u2);
  connect(less2.y, dis.u1);
  connect(minEnaTim.y, less2.u2);
  connect(onTim.y, less2.u1);
  connect(not3.y, offTim.u);
  connect(dis.y, and2.u1);
  connect(andOpe.y, not1.u);
  connect(not1.y, and2.u2);

  connect(kMinU.y, y1);
  connect(and2.y, pre1.u);
  connect(pre1.y, booToRea.u);
  connect(pre1.y, onTim.u);
  connect(pre1.y, not3.u);
  connect(booToRea.y, kMinU.u);
  connect(booToRea.y, y2);
  connect(TWetBul, pro.u2);
  connect(wseCHWST, greater.u1);
  connect(wseCWST, add1.u2);
  connect(add1.y, less1.u1);
  connect(wseCHWST, less1.u2);
  connect(towTApp, sum.u[3]);
end WSEControl;

Buildings.Examples.ChillerPlant.BaseClasses.Controls.ZeroOrderHold

Information

Extends from Modelica.Blocks.Interfaces.BooleanSISO (Single Input Single Output control block with signals of type Boolean), Modelica.Blocks.Interfaces.DiscreteBlock (Base class of discrete control blocks).

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 BooleanInput	u	Connector of Boolean input signal
output BooleanOutput	y	Connector of Boolean output signal

Modelica definition

block ZeroOrderHold "Zero order hold for boolean variable"
  extends Modelica.Blocks.Interfaces.BooleanSISO;
  extends Modelica.Blocks.Interfaces.DiscreteBlock;
protected 
  Boolean ySample;
algorithm 
  when {sampleTrigger,initial()} then
    y := ySample;
    ySample := u;
  end when;
end ZeroOrderHold;