Buildings.Controls.OBC.CDL.Reals.Sources

Package with blocks that generate source signals

Information

Package with blocks that generate signals.

Package Content

Name	Description
CalendarTime	Computes the unix time stamp and calendar time from the simulation time
CivilTime	Civil time
Constant	Output constant signal of type Real
Pulse	Generate pulse signal of type Real
Ramp	Generate ramp signal
Sin	Generate sine signal
TimeTable	Table look-up with respect to time and linear or periodic extrapolation
Validation	Collection of models that validate the continuous sources blocks of the CDL

Buildings.Controls.OBC.CDL.Reals.Sources.CalendarTime

Computes the unix time stamp and calendar time from the simulation time

Information

Block that outputs minute, hour, day of the month, month, year and weekday.

Assumption and limitations

The implementation only supports date computations from year 2010 up to and including 2020. Daylight saving and time zones are not supported.

Typical use and important parameters

The user must define which time and date correspond to time = 0 using the model parameters zerTim, and, if zerTim == CDL.Types.ZeroTime.Custom, the parameter yearRef. The user can choose from new year, midnight for a number of years: 2010 to 2020 and also 1970. The latter corresponds to a unix stamp of 0. Note that when choosing the reference time equal to 0 at 1970, the actual simulation time must be within the 2010-2020 range. For example, startTime = 1262304000 corresponds to the simulation starting on the 1st of January 2010 local time when setting zerTim = CDL.Types.ZeroTime.UnixTimeStamp. This is within the 2010-2020 range and is therefore allowed.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Reals.Sources.CivilTime

Civil time

Information

Block that outputs the civil time.

Implementation

This block outputs the time of the model. In the case of a building automation system, the building automation system synchronizes time, and hence need to assign a value for the output of this block. Daylight saving time shall not be taken into account, e.g, the block always outputs civil time rather than daylight savings time.

If a simulation starts at t=-1, then this block outputs first t=-1, and its output is advanced at the same rate as the simulation time.

Note that the block has not been included in the ASHRAE Standard 231p. However, in the future versions of the ASHRAE 231 Standard, the block should be added.

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Reals.Sources.Constant

Output constant signal of type Real

Information

Block that outputs a constant signal y = k, where k is a real-valued parameter.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Reals.Sources.Pulse

Generate pulse signal of type Real

Information

Block that outputs a pulse signal as shown below.

The pulse signal is generated an infinite number of times, and aligned with time=shift.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Reals.Sources.Ramp

Generate ramp signal

Information

The Real output y is a ramp signal:

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Reals.Sources.Sin

Generate sine signal

Information

Block that outputs a sine.

Parameters

Connectors

Modelica definition

Buildings.Controls.OBC.CDL.Reals.Sources.TimeTable

Table look-up with respect to time and linear or periodic extrapolation

Information

Block that outputs values of a time table.

The block takes as a parameter a time table of a format:

table = [ 0*3600, 0;
          6*3600, 0;
          6*3600, 1;
         18*3600, 1;
         18*3600, 0;
         24*3600, 0];

where the first column is time in seconds, and the remaining column(s) are the table values. Any number of columns can be specified. The parameter smoothness determines how the table values are interpolated. The following settings are allowed:

The parameter extrapolation determines how the table values are extrapolated. The following settings are allowed:

If extrapolation === CDL.Types.Periodic, then the above example would give a schedule with periodicity of one day. The simulation can start at any time, whether it is a multiple of a day or not, and positive or negative.

The value of the parameter offset is added to the tabulated values. The parameters timeScale is used to scale the first column of the table. For example, set timeScale = 3600 if the first column is in hour (because in CDL, the time unit is seconds).

If the table has only one row, no interpolation is performed and the table values of this row are just returned.

An interval boundary is defined by two identical time values following each other. For example

   table = [0, 0;
            1, 0;
            1, 1;
            2, 3;
            3, 5;
            3, 2;
            4, 4;
            5, 5];

defines three intervalls: 0..1, 1..3, 3..5. Within an interval the defined interpolation method is applied (so the table outputs within an interval are continuous if smoothness = CDL.Types.LinearSegments).

Example:

  table = [0, 0;
           1, 0;
           1, 1;
           2, 4;
           3, 9;
           4, 16];
  smoothness = CDL.Types.LinearSegments;

If, e.g., time = 1.0, the output y =  0.0 (before event), 1.0 (after event)
    e.g., time = 1.5, the output y =  2.5,
    e.g., time = 2.0, the output y =  4.0,
    e.g., time = 5.0, the output y = 23.0 (i.e., extrapolation via last 2 points).

Implementation

For simulation, no time events are generated within an interval in order that also intervals with many points do not reduce the simulation efficiency. If the table points are largely changing, it is adviseable to force time events by duplicating every time point (especially, if the model in which the table is present allows the variable step integrator to make large integrator steps). For example, if a sawtooth signal is defined with the table, it is more reliable to define the table as:

   table = [0, 0;
            1, 2;
            1, 2;
            2, 0;
            2, 0;
            3, 2;
            3, 2];

instead of

   table = [0, 0;
            1, 2;
            2, 0;
            3, 2];

because time events are then generated at every time point.

Building automation systems typically have discrete time semantics with fixed sampling times, and no notion of superdense time (in which a tabulated value can change without advancing time). Therefore, to implement a table with two equal time stamps, a CDL translator may parameterize a table in the building automation in such a way that the step change happens at the time indicated in the first column, whereas previous sampling times output the tabulated value at the last transition. For example,

table = [0, 0;
         1, 0;
         1, 1];
smoothness = CDL.Types.ConstantSegments;

may be converted such that a building automation system with a sampling time of 0.5 seconds outputs

  t = 0, 0.5, 1, ...
  y = 0, 0  , 1, ...

Parameters

Connectors

Modelica definition