Buildings.Controls.Continuous

Information

Package Content

Name	Description
LimPID	P, PI, PD, and PID controller with limited output, anti-windup compensation and setpoint weighting
PIDHysteresis	PID controller with anti-windup, output limiter and output hysteresis
PIDHysteresisTimer	PID controller with anti-windup, hysteresis and timer to prevent short cycling
SignalRanker	Ranks output signals such that y[i] >= y[i+1]
NumberOfRequests	Outputs the number of signals that are above/below a certain threshold
OffTimer	Records the time since the input changed to false
Examples	Collection of models that illustrate model use and test models

Buildings.Controls.Continuous.LimPID

Information

This model is identical to Modelica.Blocks.Continuous.LimPID except that it can be configured to have a reverse action.

If the parameter reverseAction=false (the default), then u_m < u_s increases the controller output, otherwise the controller output is decreased. Thus,

• for a heating coil with a two-way valve, set reverseAction = false,
• for a cooling coils with a two-way valve, set reverseAction = true.

Parameters

Type	Name	Default	Description
SimpleController	controllerType	Modelica.Blocks.Types.Simple...	Type of controller
Real	k	1	Gain of controller [1]
Time	Ti		Time constant of Integrator block [s]
Time	Td		Time constant of Derivative block [s]
Real	yMax	1	Upper limit of output
Real	yMin	0	Lower limit of output
Real	wp	1	Set-point weight for Proportional block (0..1)
Real	wd	0	Set-point weight for Derivative block (0..1)
Real	Ni	0.9	Ni*Ti is time constant of anti-windup compensation
Real	Nd	10	The higher Nd, the more ideal the derivative block
Boolean	reverseAction	false	Set to true for throttling the water flow rate through a cooling coil controller
Initialization
InitPID	initType	Modelica.Blocks.Types.InitPI...	Type of initialization (1: no init, 2: steady state, 3: initial state, 4: initial output)
Boolean	limitsAtInit	true	= false, if limits are ignored during initializiation
Real	xi_start	0	Initial or guess value value for integrator output (= integrator state)
Real	xd_start	0	Initial or guess value for state of derivative block
Real	y_start	0	Initial value of output

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

Modelica definition

block LimPID 
  "P, PI, PD, and PID controller with limited output, anti-windup compensation and setpoint weighting"
  extends Modelica.Blocks.Continuous.LimPID(
    addP(k1=revAct*wp, k2=-revAct),
    addD(k1=revAct*wd, k2=-revAct),
    addI(k1=revAct, k2=-revAct),
    yMin=0,
    yMax=1);

  parameter Boolean reverseAction = false 
    "Set to true for throttling the water flow rate through a cooling coil controller";
protected 
  parameter Real revAct = if reverseAction then -1 else 1;
end LimPID;

Buildings.Controls.Continuous.PIDHysteresis

Information

Block of a controller for set point tracking with a hysteresis element that switches the controller on and off.

If the controller is off, and the control error becomes larger than eOn, then the controller switches to on and remains on until the control error is smaller than eOff. When the controller is on, the set point tracking can be done using a P-, PI-, or PID-controller. In its off-mode, the control output is zero. Thus, the parameters yMin and yMax are used to constrain the output of the controller during its on mode only. This can be used, for example, to modulate a device between 0.3 and 1.0, and switch it to off when the control error is small enough.

Parameters

Type	Name	Default	Description
Hysteresis
Real	eOn	1	if off and control error > eOn, switch to set point tracking
Real	eOff	-eOn	if on and control error < eOff, set y=0
Boolean	pre_y_start	false	Value of hysteresis output at initial time
Set point tracking
SimpleController	controllerType	Modelica.Blocks.Types.Simple...	Type of controller
Real	k	1	Gain of controller
Time	Ti		Time constant of Integrator block [s]
Time	Td		Time constant of Derivative block [s]
Real	yMax	1	Upper limit of output
Real	yMin	0	Lower limit of output
Real	wp	1	Set-point weight for Proportional block (0..1)
Real	wd	0	Set-point weight for Derivative block (0..1)
Real	Ni	0.9	Ni*Ti is time constant of anti-windup compensation
Real	Nd	10	The higher Nd, the more ideal the derivative block
Boolean	reverseAction	false	Set to true to enable reverse action (such as for a cooling coil controller)
Initialization
InitPID	initType	Modelica.Blocks.Types.InitPI...	Type of initialization (1: no init, 2: steady state, 3: initial state, 4: initial output)
Boolean	limitsAtInit	true	= false, if limits are ignored during initializiation
Real	xi_start	0	Initial or guess value value for integrator output (= integrator state)
Real	xd_start	0	Initial or guess value for state of derivative block
Real	y_start	0	Initial value of output

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

Modelica definition

model PIDHysteresis 
  "PID controller with anti-windup, output limiter and output hysteresis"
  extends Modelica.Blocks.Interfaces.SVcontrol;

  parameter Real eOn = 1 
    "if off and control error > eOn, switch to set point tracking";
  parameter Real eOff = -eOn "if on and control error < eOff, set y=0";
  parameter Boolean pre_y_start=false 
    "Value of hysteresis output at initial time";

  parameter Modelica.Blocks.Types.SimpleController controllerType=Modelica.Blocks.Types.SimpleController.PID 
    "Type of controller";
  parameter Real k=1 "Gain of controller";
  parameter Modelica.SIunits.Time Ti "Time constant of Integrator block";
  parameter Modelica.SIunits.Time Td "Time constant of Derivative block";
  parameter Real yMax=1 "Upper limit of output";
  parameter Real yMin=0 "Lower limit of output";
  parameter Real wp=1 "Set-point weight for Proportional block (0..1)";
  parameter Real wd=0 "Set-point weight for Derivative block (0..1)";
  parameter Real Ni=0.9 "Ni*Ti is time constant of anti-windup compensation";
  parameter Real Nd=10 "The higher Nd, the more ideal the derivative block";
  parameter Boolean reverseAction = false 
    "Set to true to enable reverse action (such as for a cooling coil controller)";

  parameter Modelica.Blocks.Types.InitPID initType=Modelica.Blocks.Types.InitPID.DoNotUse_InitialIntegratorState 
    "Type of initialization (1: no init, 2: steady state, 3: initial state, 4: initial output)";
  parameter Boolean limitsAtInit=true 
    "= false, if limits are ignored during initializiation";
  parameter Real xi_start=0 
    "Initial or guess value value for integrator output (= integrator state)";
  parameter Real xd_start=0 
    "Initial or guess value for state of derivative block";
  parameter Real y_start=0 "Initial value of output";

  LimPID PID(
    controllerType=controllerType,
    k=k,
    Ti=Ti,
    yMax=yMax,
    yMin=yMin,
    wp=wp,
    wd=wd,
    Ni=Ni,
    Nd=Nd,
    initType=initType,
    limitsAtInit=limitsAtInit,
    xi_start=xi_start,
    xd_start=xd_start,
    y_start=y_start,
    Td=Td,
    reverseAction=reverseAction) "Controller for room temperature";
  Modelica.Blocks.Logical.Hysteresis hys(
    pre_y_start=pre_y_start,
    uLow=eOff,
    uHigh=eOn) "Hysteresis element to switch controller on and off";
  Modelica.Blocks.Logical.Switch swi;
  Modelica.Blocks.Sources.Constant zer(k=0) "Zero signal";
  Modelica.Blocks.Math.Feedback feeBac;
  Modelica.Blocks.Logical.Switch swi1;

equation 
  assert(eOff < eOn, "Wrong controller parameters. Require eOff < eOn.");
  connect(zer.y, swi.u3);
  connect(swi.y, y);
  connect(u_m, PID.u_m);
  connect(hys.y, swi.u2);
  connect(PID.y, swi.u1);
  connect(u_s, feeBac.u1);
  connect(u_m, feeBac.u2);
  connect(feeBac.y, hys.u);
  connect(u_s, swi1.u1);
  connect(hys.y, swi1.u2);
  connect(u_m, swi1.u3);
  connect(swi1.y, PID.u_s);
end PIDHysteresis;

Buildings.Controls.Continuous.PIDHysteresisTimer

Information

Block of a controller for set point tracking with a hysteresis element that switches the controller on and off, and a timer that prevents the controller to short cycle.

The controller is similar to Buildings.Controls.Continuous.PIDHysteresis but in addition, it has a timer that prevents the controller from switching to on too fast. When the controller switches off, the timer starts and avoids the controller from switching on until minOffTime seconds elapsed.

Parameters

Type	Name	Default	Description
On/off controller
Real	minOffTime	600	Minimum time that devices needs to be off before it can run again
Real	eOn	1	if off and control error > eOn, switch to set point tracking
Real	eOff	-eOn	if on and control error < eOff, set y=0
Boolean	pre_y_start	false	Value of hysteresis output at initial time
Set point tracking
SimpleController	controllerType	Modelica.Blocks.Types.Simple...	Type of controller
Real	k	1	Gain of controller
Time	Ti		Time constant of Integrator block [s]
Time	Td		Time constant of Derivative block [s]
Real	yMax	1	Upper limit of modulating output
Real	yMin	0.3	Lower limit of modulating output (before switch to 0)
Real	wp	1	Set-point weight for Proportional block (0..1)
Real	wd	0	Set-point weight for Derivative block (0..1)
Real	Ni	0.9	Ni*Ti is time constant of anti-windup compensation
Real	Nd	10	The higher Nd, the more ideal the derivative block
Boolean	reverseAction	false	Set to true to enable reverse action (such as for a cooling coil controller)
Initialization
InitPID	initType	Modelica.Blocks.Types.InitPI...	Type of initialization (1: no init, 2: steady state, 3: initial state, 4: initial output)
Boolean	limitsAtInit	true	= false, if limits are ignored during initializiation
Real	xi_start	0	Initial or guess value value for integrator output (= integrator state)
Real	xd_start	0	Initial or guess value for state of derivative block
Real	y_start	0	Initial value of output

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
output RealOutput	tOn	Time since boiler switched on
output RealOutput	tOff	Time since boiler switched off
output BooleanOutput	on	Outputs true if boiler is on

Modelica definition

model PIDHysteresisTimer 
  "PID controller with anti-windup, hysteresis and timer to prevent short cycling"
  extends Modelica.Blocks.Interfaces.SVcontrol;

  parameter Real minOffTime=600 
    "Minimum time that devices needs to be off before it can run again";
  parameter Real eOn = 1 
    "if off and control error > eOn, switch to set point tracking";
  parameter Real eOff = -eOn "if on and control error < eOff, set y=0";
  parameter Boolean pre_y_start=false 
    "Value of hysteresis output at initial time";

  parameter Modelica.Blocks.Types.SimpleController controllerType=Modelica.Blocks.Types.SimpleController.PID 
    "Type of controller";
  parameter Real k=1 "Gain of controller";
  parameter Modelica.SIunits.Time Ti "Time constant of Integrator block";
  parameter Modelica.SIunits.Time Td "Time constant of Derivative block";
  parameter Real yMax=1 "Upper limit of modulating output";
  parameter Real yMin=0.3 
    "Lower limit of modulating output (before switch to 0)";
  parameter Real wp=1 "Set-point weight for Proportional block (0..1)";
  parameter Real wd=0 "Set-point weight for Derivative block (0..1)";
  parameter Real Ni=0.9 "Ni*Ti is time constant of anti-windup compensation";
  parameter Real Nd=10 "The higher Nd, the more ideal the derivative block";
  parameter Boolean reverseAction = false 
    "Set to true to enable reverse action (such as for a cooling coil controller)";

  parameter Modelica.Blocks.Types.InitPID initType=Modelica.Blocks.Types.InitPID.DoNotUse_InitialIntegratorState 
    "Type of initialization (1: no init, 2: steady state, 3: initial state, 4: initial output)";
  parameter Boolean limitsAtInit=true 
    "= false, if limits are ignored during initializiation";
  parameter Real xi_start=0 
    "Initial or guess value value for integrator output (= integrator state)";
  parameter Real xd_start=0 
    "Initial or guess value for state of derivative block";
  parameter Real y_start=0 "Initial value of output";

  Modelica.Blocks.Interfaces.RealOutput tOn "Time since boiler switched on";
  Modelica.Blocks.Interfaces.RealOutput tOff "Time since boiler switched off";

  LimPID con(
    controllerType=controllerType,
    k=k,
    Ti=Ti,
    Td=Td,
    wp=wp,
    wd=wd,
    Ni=Ni,
    Nd=Nd,
    initType=initType,
    limitsAtInit=limitsAtInit,
    xi_start=xi_start,
    xd_start=xd_start,
    y_start=y_start,
    final yMin=yMin,
    final yMax=yMax,
    reverseAction=reverseAction) "Controller to track setpoint";
protected 
  Modelica.Blocks.Sources.Constant zer(k=0) "Zero signal";
  Modelica.Blocks.Logical.Switch switch2;
  Modelica.Blocks.Logical.GreaterEqualThreshold greaterEqualThreshold(threshold=
       minOffTime);
  Modelica.Blocks.Logical.And and3;
public 
  OffTimer offHys;
  Modelica.Blocks.Logical.Timer onTimer;
protected 
  Modelica.Blocks.Logical.Not not1;
public 
  Modelica.Blocks.Logical.Timer offTimer;
         Modelica.Blocks.Interfaces.BooleanOutput on 
    "Outputs true if boiler is on";
protected 
  Modelica.Blocks.Logical.Switch switch1;
public 
  Modelica.Blocks.Math.Feedback feeBac;
  Modelica.Blocks.Logical.Hysteresis hys(
    pre_y_start=pre_y_start,
    uLow=eOff,
    uHigh=eOn) "Hysteresis element to switch controller on and off";
equation 
  connect(u_m, con.u_m);
  connect(zer.y,switch2. u3);
  connect(switch2.y, y);
  connect(and3.y,switch2. u2);
  connect(greaterEqualThreshold.y, and3.u1);
  connect(offHys.y, greaterEqualThreshold.u);
  connect(con.y,switch2. u1);
  connect(onTimer.y, tOn);
  connect(offTimer.y, tOff);
  connect(and3.y, on);
  connect(and3.y, onTimer.u);
  connect(and3.y, not1.u);
  connect(not1.y, offTimer.u);
  connect(and3.y, switch1.u2);
  connect(u_s, switch1.u1);
  connect(u_m, switch1.u3);
  connect(switch1.y, con.u_s);
  connect(u_s, feeBac.u1);
  connect(u_m, feeBac.u2);
  connect(feeBac.y, hys.u);
  connect(hys.y, offHys.u);
  connect(hys.y, and3.u2);
end PIDHysteresisTimer;

Buildings.Controls.Continuous.SignalRanker

Information

Block that sorts the input signal u[:] such that the output signal satisfies y[i] >= y[i+1] for all i=1, ..., nin-1.

This block may for example be used in a variable air volume flow controller to access the position of the dampers that are most open.

Parameters

Type	Name	Default	Description
Integer	nin	1	Number of inputs
Integer	nout	nin	Number of outputs

Connectors

Type	Name	Description
input RealInput	u[nin]	Connector of Real input signals
output RealOutput	y[nout]	Connector of Real output signals

Modelica definition

block SignalRanker "Ranks output signals such that y[i] >= y[i+1]"
   extends Modelica.Blocks.Interfaces.MIMO(final nout=nin);
protected 
  Real t "Temporary variable";
algorithm 
  y[:] := u[:];
  for i in 1:nin loop
    for j in 1:nin-1 loop
    if y[j] < y[j+1] then
      t      := y[j+1];
      y[j+1] := y[j];
      y[j]   := t;
    end if;
   end for;
  end for;
end SignalRanker;

Buildings.Controls.Continuous.NumberOfRequests

Information

Block that outputs the number of inputs that exceed a threshold. The parameter kind is used to determine the kind of the inequality. The table below shows the allowed settings.

This model may be used to check how many rooms exceed a temperature threshold.

Parameters

Type	Name	Default	Description
Integer	nin		Number of inputs
Real	threShold	0	Threshold
Integer	kind		Set to 0 for u>threShold, to 1 for >=, to 2 for <= or to 3 for <

Connectors

Type	Name	Description
output IntegerOutput	y	Number of input signals that violate the threshold
input RealInput	u[nin]	Input signals

Modelica definition

block NumberOfRequests 
  "Outputs the number of signals that are above/below a certain threshold"
   extends Modelica.Blocks.Interfaces.BlockIcon;

  parameter Integer nin "Number of inputs";
  parameter Real threShold = 0 "Threshold";
  parameter Integer kind 
    "Set to 0 for u>threShold, to 1 for >=, to 2 for <= or to 3 for <";
  Modelica.Blocks.Interfaces.IntegerOutput y 
    "Number of input signals that violate the threshold";
  Modelica.Blocks.Interfaces.RealInput u[nin] "Input signals";
algorithm 
  y := 0;
  for i in 1:nin loop
    if kind == 0 then
      if u[i] > threShold then
        y := y+1;
      end if;
    end if;
    if kind == 1 then
      if u[i] >= threShold then
        y := y+1;
      end if;
    end if;
    if kind == 2 then
      if u[i] <= threShold then
        y := y+1;
      end if;
    end if;
    if kind == 3 then
      if u[i] < threShold then
        y := y+1;
      end if;
    end if;
  end for;
end NumberOfRequests;

Buildings.Controls.Continuous.OffTimer

Information

Block that records the time that has elapsed since its input signal switched to false.

At the beginning of the simulation, this block outputs the time that has elapsed since the start of the simulation. Afterwards, whenever its input switches to false, the timer is reset.

Connectors

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

Modelica definition

model OffTimer "Records the time since the input changed to false"
  extends Modelica.Blocks.Interfaces.partialBooleanBlockIcon;

  Modelica.Blocks.Interfaces.BooleanInput u "Connector of Boolean input signal";
  Modelica.Blocks.Interfaces.RealOutput y "Connector of Real output signal";

protected 
  discrete Modelica.SIunits.Time entryTime "Time instant when u became true";
initial equation 
  pre(entryTime) = 0;
equation 
  when (not u) then
    entryTime = time;
  end when;
  y = time - entryTime;
end OffTimer;