Buildings.Controls.OBC.UsersGuide

User's Guide

Information

The package Buildings.Controls.OBC contains the Control Description Language (CDL) and models for building control that are implemented using CDL. The Control Description Language is a language that is being standardized through ASHRAE Standard 231P. It has been developed to digitalize the design, implementation and commissioning of building control sequences in format that is independent of any particular control product line (Wetter et al., 2018). For a description of the process for digitalizing control delivery, see Wetter et al. (2022).

The Control Description Language and the library of control sequences have been developed in the OpenBuildingControl project, see obc.lbl.gov.

This package contains control sequences for

HVAC airside system control Buildings.Controls.OBC.ASHRAE.G36,
radiant heating and cooling systems Buildings.Controls.OBC.RadiantSystems,
outdoor lighting control Buildings.Controls.OBC.OutdoorLights, and
shading device control Buildings.Controls.OBC.Shade.

The control sequences are composed of the elementary blocks from the package Buildings.Controls.OBC.CDL.

The package also contains models for unit conversions, Buildings.Controls.OBC.UnitConversions, and utilities models, such as Buildings.Controls.OBC.Utilities.OptimalStart, which output the optimal start time for an HVAC system.

The Control Description Language (CDL) can be found in Buildings.Controls.OBC.CDL and its specification is at obc.lbl.gov. Note that the implementation in Buildings.Controls.OBC.CDL replicates some classes from the Modelica Standard Library. This was done to have a self-contained implementation of CDL that can be standardized through ASHRAE and that has minimum dependencies on other software to ease support by building automation systems. The replication of the implementation of the blocks also avoids that CDL inadvertently changes if the Modelica Standard Library is updated, which is undesirable as changes to CDL will need to go through the ASHRAE standardization process.

References

Michael Wetter, Milica Grahovac and Jianjun Hu.
Control Description Language.
1st American Modelica Conference, Cambridge, MA, USA, August 2018.
https://doi.org/10.3384/ecp1815417.
Michael Wetter, Paul Ehrlich, Antoine Gautier, Milica Grahovac, Philip Haves, Jianjun Hu, Anand Prakash, Dave Robin and Kun Zhang.
OpenBuildingControl: Digitizing the control delivery from building energy modeling to specification, implementation and formal verification.
Energy, Volume 238, Part A, January 2022.
https://doi.org/10.1016/j.energy.2021.121501.

Extends from Modelica.Icons.Information (Icon for general information packages).

Package Content

Name	Description
Conventions	Naming conventions in OBC package

Buildings.Controls.OBC.UsersGuide.Conventions

Naming conventions in OBC package

Information

The Buildings.Controls.OBC package follows the naming conventions of the Buildings Library, see Buildings.UsersGuide.Conventions. The table below shows some examples of commonly used names. Note that the names are generally composed as follows:

If needed to understand the context, a prefix u for input or y for output may be used.
Next, the quantity is used, such as TOut or TZonHea.
Finally, as a postfix a qualifier may be added, such as Set for set point, Min for minimum, or Coo for cooling.

Generally, we strive for short names, and therefore often prefix or postfix are omitted if the type of the variable is clear from the context. For example, a room temperature thermostat may simply use T as an input as it is clear that this will be the room temperature.

Name	Comments
Instance names
`TOut` (`hOut`)	Outdoor air temperature (enthalpy)
`TZonHeaSet` (`TZonCooSet`)	Zone heating (cooling) set point temperature
`VDis_flow`	Measured discharge airflow rate
`dpBui`	Building static pressure difference, relative to ambient
`uOpeMod`	Zone group operating mode
`uResReq`	Number of reset requests
`uSupFan`	Current supply fan enabling status, `true`: fan is enabled
`uSupFanSpe`	Current supply fan speed
`uDam`	Measured damper position
`uHea` (`uCoo`)	Heating (cooling) loop signal
`yPosMin` (`yPosMax`)	Minimum (maximum) position
`yHeaCoi` (`yCooCoi`)	Heating (cooling) coil control signal
`uChiIsoVal`	Chiller condenser water isolation valve status
`dpChiWat_remote`	Chilled water differntial statis pressure from remote sensor
`TChiWatRet`	Chilled water return temperature
`VChiWat_flow`	Measured chilled water volume flow rate
`uHeaPreCon`	Chiller head pressure control loop signal from chiller controller
`yChiPumSpe`	Chilled water pump speed setpoint
`yChi`	Chiller status setpoint
`yMinValPos`	Minimum valve position setpoint
Parameter names
Name	Comments
`use_TMix`	Set to `true` if mixed air temperature measurement is used
`have_occSen` (`have_winSen`)	Set to `true` if the zone has occupancy (window) sensor
`AFlo`	Area of the zone
`VDisHeaSetMax_flow` (`VDisCooSetMax_flow`)	Zone maximum heating (cooling) airflow set point
`VOutPerAre_flow` (`VOutPerPer_flow`)	Outdoor airflow rate per unit area (person)
`V_flow_nominal`	Nominal volume flow rate
`VOutMin_flow`	Calculated minimum outdoor airflow rate at design stage
`pMinSet` (`pMaxSet`)	Minimum (maximum) pressure set point for fan speed control
`TSupSetMin` (`TSupSetMax`)	Lowest (Highest) cooling supply air temperature
`TOccHeaSet` (`TUnoHeaSet`)	Zone occupied (unoccupied) heating set point
`TZonCooMax` (`TZonCooMin`)	Maximum (minimum) zone cooling set point when cooling is on
`retDamPhyPosMax` (`outDamPhyPosMax`)	Physically fixed maximum position of the return (outdoor) air damper
`samplePeriod`	Sample period
`zonDisEffHea` (`zonDisEffCoo`)	Zone air distribution effectiveness during heating (cooling)
`kCoo`	Gain for cooling control loop signal
`TiCoo`	Time constant of integrator block for cooling control loop signal
`TdCoo`	Time constant of derivative block for cooling control loop signal
`nChi`	Total number of chillers
`have_parChi`	True: the plant has parallel chillers
`have_heaChiWatPum`	True: the plant has headed chilled water pumps
`have_fixSpeConWatPum`	True: the plant has fixed speed condenser water pumps
`need_reduceChillerDemand`	True: the plant needs to limit chiller demand when chiller staging
`minChiLif`	Minimum allowable lift at minimum load for chiller
`TChiWatSupMin`	Minimum chilled water supply temperature
`dpChiWatPumMin`	Minimum chilled water pump differential static pressure
`lift_min`	Chiller minimum lift

Extends from Modelica.Icons.Information (Icon for general information packages).

Modelica definition

class Conventions "Naming conventions in OBC package" extends Modelica.Icons.Information; end Conventions;