Buildings.Utilities.IO.BCVTB

Package Content

Name	Description
UsersGuide	User's Guide
BaseClasses	Package with base classes for BCVTB interface
BCVTB	Block that exchanges data with the Building Controls Virtual Test Bed
Examples	Collection of models that illustrate model use and test models
MoistAirInterface	Fluid interface that can be coupled to BCVTB for medium that model the air humidity
To_degC	Converts Kelvin to Celsius
From_degC	Converts Celsius to Kelvin

Buildings.Utilities.IO.BCVTB.BCVTB

Information

At the start of the simulation, this block establishes a socket connection using the Berkeley Software Distribution socket (BSD socket). At each sampling interval, data are exchanged between Modelica and the BCVTB. When Dymola terminates, a signal is sent to the BCVTB so that it can terminate gracefully.

For each element in the input vector uR[nDblWri], the value of the flag flaDblWri[nDblWri] determines whether the current value, the average over the sampling interval or the integral over the sampling interval is sent to the BCVTB. The following three options are allowed:

flaDblWri[i]	Value sent to the BCVTB
0	Current value of uR[i]
1	Average value of uR[i] over the sampling interval
2	Integral of uR[i] over the sampling interval

For the first call to the BCVTB interface, the value of the parameter uStart[nDblWri] will be used instead of uR[nDblWri]. This avoids an algebraic loop when determining the initial conditions. If uR[nDblWri] were to be used, then computing the initial conditions may require an iterative solution in which the function exchangeWithSocket may be called multiple times. Unfortunately, it does not seem possible to use a parameter that would give a user the option to either select uR[i] or uStart[i] in the first data exchange. The reason is that the symbolic solver does not evaluate the test that picks uR[i] or uStart[i], and hence there would be an algebraic loop.

If the parameter activateInterface is set to false, then no data is exchanged with the BCVTB. The output of this block is then equal to the value of the parameter yRFixed[nDblRea]. This option can be helpful during debugging. Since during model translation, the functions are still linked to the C library, the header files and libraries need to be present in the current working directory even if activateInterface=false.

Extends from Modelica.Blocks.Interfaces.DiscreteBlock (Base class of discrete control blocks).

Parameters

Type	Name	Default	Description
Time	samplePeriod	if activateInterface then ti...	Sample period of component [s]
Time	startTime	0	First sample time instant [s]
Boolean	activateInterface	true	Set to false to deactivate interface and use instead yFixed as output
Time	timeStep		Time step used for the synchronization [s]
String	xmlFileName	"socket.cfg"	Name of the file that is generated by the BCVTB and that contains the socket information
Integer	nDblWri		Number of double values to write to the BCVTB
Integer	nDblRea		Number of double values to be read from the BCVTB
Integer	flaDblWri[nDblWri]	zeros(nDblWri)	Flag for double values (0: use current value, 1: use average over interval, 2: use integral over interval)
Real	uStart[nDblWri]		Initial input signal, used during first data transfer with BCVTB
Real	yRFixed[nDblRea]	zeros(nDblRea)	Fixed output, used if activateInterface=false

Connectors

Type	Name	Description
input RealInput	uR[nDblWri]	Real inputs to be sent to the BCVTB
output RealOutput	yR[nDblRea]	Real outputs received from the BCVTB

Modelica definition

model BCVTB 
  "Block that exchanges data with the Building Controls Virtual Test Bed"
  extends Modelica.Blocks.Interfaces.DiscreteBlock(final startTime=0,
  final samplePeriod = if activateInterface then timeStep else Modelica.Constants.inf);
  parameter Boolean activateInterface = true 
    "Set to false to deactivate interface and use instead yFixed as output";
  parameter Modelica.SIunits.Time timeStep 
    "Time step used for the synchronization";
  parameter String xmlFileName = "socket.cfg" 
    "Name of the file that is generated by the BCVTB and that contains the socket information";
  parameter Integer nDblWri(min=0) 
    "Number of double values to write to the BCVTB";
  parameter Integer nDblRea(min=0) 
    "Number of double values to be read from the BCVTB";
  parameter Integer flaDblWri[nDblWri] = zeros(nDblWri) 
    "Flag for double values (0: use current value, 1: use average over interval, 2: use integral over interval)";
  parameter Real uStart[nDblWri] 
    "Initial input signal, used during first data transfer with BCVTB";
  parameter Real yRFixed[nDblRea] = zeros(nDblRea) 
    "Fixed output, used if activateInterface=false";

  Modelica.Blocks.Interfaces.RealInput uR[nDblWri] 
    "Real inputs to be sent to the BCVTB";
  Modelica.Blocks.Interfaces.RealOutput yR[nDblRea] 
    "Real outputs received from the BCVTB";

 Integer flaRea "Flag received from BCVTB";
 Modelica.SIunits.Time simTimRea 
    "Current simulation time received from the BCVTB";
 Integer retVal "Return value from the BSD socket data exchange";
protected 
  parameter Integer socketFD(fixed=false) 
    "Socket file descripter, or a negative value if an error occured";
  parameter Real _uStart[nDblWri](fixed=false) 
    "Initial input signal, used during first data transfer with BCVTB";
  constant Integer flaWri=0;
  Real uRInt[nDblWri] "Value of integral";
  Real uRIntPre[nDblWri] "Value of integral at previous sampling instance";
public 
  Real uRWri[nDblWri] "Value to be sent to the interface";
initial algorithm 
  socketFD :=if activateInterface then 
      Buildings.Utilities.IO.BCVTB.BaseClasses.establishClientSocket(xmlFileName=xmlFileName) else 
      0;
    // check for valid socketFD
     assert(socketFD >= 0, "Socket file descripter for BCVTB must be positive.\n" +
                         "   A negative value indicates that no connection\n" +
                         "   could be established. Check file 'utilSocket.log'.\n" +
                         "   Received: socketFD = " + integerString(socketFD));
   flaRea   := 0;
   uRInt    := zeros(nDblWri);
   uRIntPre := zeros(nDblWri);
   for i in 1:nDblWri loop
     assert(flaDblWri[i]>=0 and flaDblWri[i]<=2,
        "Parameter flaDblWri out of range for " + integerString(i) + "-th component.");
     if (flaDblWri[i] == 0) then
        _uStart[i] := uStart[i];               // Current value.
     elseif (flaDblWri[i] == 1) then
        _uStart[i] := uStart[i];                // Average over interval
     else
        _uStart[i] := uStart[i]*samplePeriod;  // Integral over the sampling interval
                                               // This is multiplied with samplePeriod because if
                                               // u is power, then uRWri needs to be energy.

     end if;
   end for;

equation 
   for i in 1:nDblWri loop
      der(uRInt[i]) = if (flaDblWri[i] > 0) then uR[i] else 0;
   end for;
algorithm 
  when {sampleTrigger} then
    assert(flaRea == 0, "BCVTB interface attempts to exchange data after Ptolemy reached its final time.\n" +
                        "   Aborting simulation. Check final time in Modelica and in Ptolemy.\n" +
                        "   Received: flaRea = " + integerString(flaRea));
     // Compute value that will be sent to the BCVTB interface
     for i in 1:nDblWri loop
       if (flaDblWri[i] == 0) then
         uRWri[i] :=pre(uR[i]);  // Send the current value.
                                 // Without the pre(), Dymola 7.2 crashes during translation of Examples.MoistAir
       else
         uRWri[i] :=uRInt[i] - uRIntPre[i]; // Integral over the sampling interval
         if (flaDblWri[i] == 1) then
            uRWri[i] := uRWri[i]/samplePeriod;   // Average value over the sampling interval
         end if;
       end if;
      end for;

    // Exchange data
    if activateInterface then
      (flaRea, simTimRea, yR, retVal) :=
        Buildings.Utilities.IO.BCVTB.BaseClasses.exchangeReals(
        socketFD=socketFD,
        flaWri=flaWri,
        simTimWri=time,
        dblValWri=if firstTrigger then _uStart else uRWri,
        nDblWri=size(uRWri, 1),
        nDblRea=size(yR, 1));
    else
      flaRea := 0;
      simTimRea := time;
      yR := yRFixed;
      retVal := 0;
      end if;
    // Check for valid return flags
    assert(flaRea >= 0, "BCVTB sent a negative flag to Modelica during data transfer.\n" +
                        "   Aborting simulation. Check file 'utilSocket.log'.\n" +
                        "   Received: flaRea = " + integerString(flaRea));
    assert(retVal >= 0, "Obtained negative return value during data transfer with BCVTB.\n" +
                        "   Aborting simulation. Check file 'utilSocket.log'.\n" +
                        "   Received: retVal = " + integerString(retVal));

    // Store current value of integral
    uRIntPre:=uRInt;
  end when;
   // Close socket connnection
   when terminal() then
     if activateInterface then
        Buildings.Utilities.IO.BCVTB.BaseClasses.closeClientSocket(
                                                          socketFD);
     end if;
   end when;

end BCVTB;

Buildings.Utilities.IO.BCVTB.MoistAirInterface

Information

The model takes as input signals the temperature and water vapor concentration and, optionally, a bulk mass flow rate into or out of the system boundary. The state of the fluid that flows out of this model will be at this temperature and water vapor concentration. The output of this model are the sensible and latent heat exchanged across the system boundary.

When used with the BCVTB, a building simulation program such as EnergyPlus may compute the room air temperatures and room air humidity rate, which is then used as an input to this model. The sensible and latent heat flow rates may be sent to EnergyPlus to couple the air-conditioning system to the energy balance of the building model.

Note: The EnergyPlus building simulation program outputs the absolute humidity ratio in units of [kg/kg dry air]. Since Modelica.Media uses [kg/kg total mass of air], this quantity needs to be converted. The conversion can be done with the model Buildings.Utilities.Psychrometrics.ToTotalAir.

Extends from Buildings.Utilities.IO.BCVTB.BaseClasses.FluidInterface (Partial class for fluid interface that can be coupled to BCVTB).

Parameters

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium model within the source
Boolean	use_m_flow_in	false	Get the mass flow rate from the input connector
MassFlowRate	m_flow	0	Fixed mass flow rate going out of the fluid port [kg/s]

Connectors

Type	Name	Description
input RealInput	m_flow_in	Prescribed mass flow rate
input RealInput	T_in	Prescribed boundary temperature
FluidPorts_b	ports[nPorts]
output RealOutput	HSen_flow	Sensible enthalpy flow rate, positive if flow into the component [W]
output RealOutput	HLat_flow	Latent enthalpy flow rate, positive if flow into the component [W]
input RealInput	phi	Medium relative humidity

Modelica definition

model MoistAirInterface 
  "Fluid interface that can be coupled to BCVTB for medium that model the air humidity"
  extends Buildings.Utilities.IO.BCVTB.BaseClasses.FluidInterface(bou(
        final use_X_in=true));

  Modelica.Blocks.Interfaces.RealOutput HLat_flow(unit="W") 
    "Latent enthalpy flow rate, positive if flow into the component";
  Buildings.Fluid.Sensors.SensibleEnthalpyFlowRate senEntFloRat[nPorts](
      redeclare package Medium = Medium) "Sensible enthalpy flow rates";
public 
  Modelica.Blocks.Math.Sum sumHSen_flow(nin=nPorts) 
    "Sum of sensible enthalpy flow rates";
  Modelica.Blocks.Math.Feedback diff 
    "Difference between total and sensible enthalpy flow rate";
  Modelica.Blocks.Interfaces.RealInput phi "Medium relative humidity";
  Buildings.Utilities.Psychrometrics.X_pTphi masFra(
                                           use_p_in=false, redeclare package
      Medium = Medium) "Mass fraction";
equation 
  for i in 1:nPorts loop
  connect(senEntFloRat[i].port_a, ports[i]);
  connect(senEntFloRat[i].H_flow, sumHSen_flow.u[i]);
  end for;
  connect(senEntFloRat.port_b, totEntFloRat.port_a);
  connect(sumHSen_flow.y, HSen_flow);
  connect(sumHTot_flow.y, diff.u1);
  connect(diff.y, HLat_flow);
  connect(diff.u2, sumHSen_flow.y);
  connect(masFra.T, T_in);
  connect(masFra.phi, phi);
  connect(masFra.X, bou.X_in);
end MoistAirInterface;

Buildings.Utilities.IO.BCVTB.To_degC

Information

Converts the input from degree Celsius to Kelvin. Note that inside Modelica, it is strongly recommended to use Kelvin. This block is provided for convenience since the BCVTB interface may couple Modelica to programs that use Celsius as the unit for temperature.

Extends from Modelica.Blocks.Interfaces.BlockIcon (Basic graphical layout of input/output block).

Connectors

Type	Name	Description
input RealInput	Kelvin	Temperature in Kelvin [K]
output RealOutput	Celsius	Temperature in Celsius [degC]

Modelica definition

block To_degC "Converts Kelvin to Celsius"
  extends Modelica.Blocks.Interfaces.BlockIcon;

  Modelica.Blocks.Interfaces.RealInput Kelvin(final quantity="Temperature",
                                              final unit = "K", displayUnit = "degC", min=0) 
    "Temperature in Kelvin";
  Modelica.Blocks.Interfaces.RealOutput Celsius(final quantity="Temperature",
                                                final unit = "degC", displayUnit = "degC", min=-273.15) 
    "Temperature in Celsius";
equation 
  Kelvin = Modelica.SIunits.Conversions.from_degC(Celsius);
end To_degC;

Buildings.Utilities.IO.BCVTB.From_degC

Information

Converts the input from Kelvin to degree Celsius. Note that inside Modelica, by convention, all models use Kelvin. This block is provided for convenience since the BCVTB interface may couple Modelica to programs that use Celsius as the unit for temperature.

Extends from Modelica.Blocks.Interfaces.BlockIcon (Basic graphical layout of input/output block).

Connectors

Type	Name	Description
input RealInput	Celsius	Temperature in Celsius [degC]
output RealOutput	Kelvin	Temperature in Kelvin [K]

Modelica definition

block From_degC "Converts Celsius to Kelvin"
  extends Modelica.Blocks.Interfaces.BlockIcon;

  Modelica.Blocks.Interfaces.RealInput Celsius(final quantity="Temperature",
                                               final unit = "degC", displayUnit = "degC", min=-273.15) 
    "Temperature in Celsius";
  Modelica.Blocks.Interfaces.RealOutput Kelvin(final quantity="Temperature",
                                               final unit = "K", displayUnit = "degC", min=0) 
    "Temperature in Kelvin";
equation 
  Celsius = Modelica.SIunits.Conversions.to_degC(Kelvin);
end From_degC;