Buildings.Templates.Plants.Controls.MinimumFlow
Package of sequences for minimum flow bypass valve
Information
This package contains control sequences for the HW or CHW minimum flow bypass valve.
Package Content
| Name | Description |
|---|---|
 Controller
|
Minimum flow bypass valve controller |
 ControllerDualMode
|
CHW and/or HW minimum flow bypass valve controller |
 Setpoint
|
Minimum flow setpoint calculation |
 Validation
|
Collection of validation models |
Buildings.Templates.Plants.Controls.MinimumFlow.Controller
Minimum flow bypass valve controller
Information
The minimum flow bypass valve is modulated based on a reverse acting control loop to maintain the primary flow rate at setpoint. The setpoint is calculated as described in Buildings.Templates.Plants.Controls.MinimumFlow.Setpoint.
When using isolation valve command signals
(have_valInlIso=true or have_valOutIso=true):
When any valve is commanded open, the bypass valve control loop is enabled.
The valve is opened 100 % otherwise.
When enabled, the bypass valve loop shall be biased to start with the valve 100 % open.
Otherwise
(have_valInlIso=false and have_valOutIso=false):
When any primary pump is proven on, the bypass valve control loop is enabled.
The valve is opened 100 % otherwise.
When enabled, the bypass valve loop shall be biased to start with the valve 100 % open.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | have_valInlIso | Set to true to enable control loop based on inlet isolation valve command | |
| Boolean | have_valOutIso | Set to true to enable control loop based on outlet isolation valve command | |
| Real | V_flow_nominal[:] | Design flow rate – Each unit [m3/s] | |
| Real | V_flow_min[:] | Minimum flow rate – Each unit [m3/s] | |
| Real | k | 1 | Gain of controller |
| Time | Ti | 0.5 | Time constant of integrator block [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | VPri_flow | Primary volume flow rate [m3/s] |
| input BooleanInput | u1PumPri_actual[nEna] | Primary pump status |
| input BooleanInput | u1ValInlIso[nEna] | Inlet isolation valve command |
| input BooleanInput | u1ValOutIso[nEna] | Outlet isolation valve command |
| output RealOutput | y | Valve command [1] |
| input BooleanInput | u1Equ[nEqu] | Equipment enable command |
| output RealOutput | VPriSet_flow | Primary flow setpoint [m3/s] |
Modelica definition
block Controller
"Minimum flow bypass valve controller"
parameter Boolean have_valInlIso
"Set to true to enable control loop based on inlet isolation valve command";
parameter Boolean have_valOutIso
"Set to true to enable control loop based on outlet isolation valve command";
parameter Integer nEqu(
final min=1)=0
"Number of plant equipment";
parameter Integer nEna(
final min=1)=0
"Number of enable signals – Valve command or pump status";
parameter Real V_flow_nominal[:](
each final unit="m3/s")
"Design flow rate – Each unit";
parameter Real V_flow_min[:](
each final unit="m3/s")
"Minimum flow rate – Each unit";
parameter Real k(
min=0)=1
"Gain of controller";
parameter Modelica.Units.SI.Time Ti(
min=Buildings.Controls.OBC.CDL.Constants.small)=0.5
"Time constant of integrator block";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VPri_flow(
final unit="m3/s")
"Primary volume flow rate";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1PumPri_actual[nEna]
if not have_valInlIso and not have_valOutIso
"Primary pump status";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1ValInlIso[nEna]
if have_valInlIso
"Inlet isolation valve command";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1ValOutIso[nEna]
if have_valOutIso
"Outlet isolation valve command";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput y(
final unit="1")
"Valve command";
Utilities.PIDWithEnable ctl(
final k=k,
final Ti=Ti,
final reverseActing=true,
y_reset=1,
y_neutral=1)
"PI controller";
Buildings.Controls.OBC.CDL.Logical.MultiOr anyValInlIso(
final nin=nEna)
if have_valInlIso
"True if any valve commanded open";
Buildings.Controls.OBC.CDL.Logical.MultiOr anyValOutIso(
final nin=nEna)
if have_valOutIso
"True if any valve commanded open";
Buildings.Controls.OBC.CDL.Logical.MultiOr anyPumPri(
final nin=nEna)
if not have_valInlIso and not have_valOutIso
"True if any pump proven on";
Utilities.PlaceholderLogical phValInlIso(
final have_inp=have_valInlIso,
u_internal=false)
"Placeholder signal";
Utilities.PlaceholderLogical phValOutIso(
final have_inp=have_valOutIso,
u_internal=false)
"Placeholder signal";
Utilities.PlaceholderLogical phPrumPri(
final have_inp=not have_valInlIso and not have_valOutIso,
u_internal=false)
"Placeholder signal";
Buildings.Controls.OBC.CDL.Logical.MultiOr any(
nin=3)
"True if any enable condition met";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1Equ[nEqu]
"Equipment enable command";
Setpoint setFloMin(
final V_flow_nominal=V_flow_nominal,
final V_flow_min=V_flow_min,
nEqu=nEqu)
"Calculate minimum flow setpoint";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput VPriSet_flow(
final unit="m3/s")
"Primary flow setpoint";
equation
connect(anyValInlIso.u, u1ValInlIso);
connect(anyValOutIso.u, u1ValOutIso);
connect(anyPumPri.u, u1PumPri_actual);
connect(VPri_flow, ctl.u_m);
connect(anyValInlIso.y, phValInlIso.u);
connect(anyValOutIso.y, phValOutIso.u);
connect(anyPumPri.y, phPrumPri.u);
connect(phValInlIso.y, any.u[1]);
connect(phValOutIso.y, any.u[2]);
connect(phPrumPri.y, any.u[3]);
connect(any.y, ctl.uEna);
connect(ctl.y, y);
connect(u1Equ, setFloMin.u1);
connect(setFloMin.VPriSet_flow, ctl.u_s);
connect(setFloMin.VPriSet_flow, VPriSet_flow);
end Controller;
Buildings.Templates.Plants.Controls.MinimumFlow.ControllerDualMode
CHW and/or HW minimum flow bypass valve controller
Information
HW minimum flow
The HW minimum flow bypass valve is modulated based on a reverse acting control loop to maintain the primary HW flow rate at setpoint. The setpoint is calculated as described in Buildings.Templates.Plants.Controls.MinimumFlow.Setpoint using the number of units commanded on in heating mode at each stage.
When using isolation valve command signals
(have_valInlIso=true or have_valOutIso=true):
When any HW isolation valve is commanded open, the HW bypass valve control loop is enabled.
The valve is opened 100 % otherwise.
When enabled, the HW bypass valve loop shall be biased to start with the valve 100 % open.
Otherwise
(have_valInlIso=false and have_valOutIso=false):
- For heating and cooling plants with common dedicated CHW and HW pumps: When any primary pump is proven on and the associated heat pump is commanded in heating mode, the HW bypass valve control loop is enabled. The valve is opened 100 % otherwise. When enabled, the HW bypass valve loop shall be biased to start with the valve 100 % open.
- For any other plants: When any primary HW pump is proven on, the HW bypass valve control loop is enabled. The valve is opened 100 % otherwise. When enabled, the HW bypass valve loop shall be biased to start with the valve 100 % open.
CHW minimum flow
The CHW minimum flow bypass valve is modulated based on a reverse acting control loop to maintain the primary CHW flow rate at setpoint. The setpoint is calculated as described in Buildings.Templates.Plants.Controls.MinimumFlow.Setpoint using the number of units commanded on in cooling mode at each stage.
When using isolation valve command signals
(have_valInlIso=true or have_valOutIso=true):
When any CHW isolation valve is commanded open, the CHW bypass valve control loop is enabled.
The valve is opened 100 % otherwise.
When enabled, the CHW bypass valve loop shall be biased to start with the valve 100 % open.
Otherwise
(have_valInlIso=false and have_valOutIso=false):
- For heating and cooling plants with common dedicated CHW and HW pumps: When any primary pump is proven on and the associated heat pump is commanded in cooling mode, the CHW bypass valve control loop is enabled. The valve is opened 100 % otherwise. When enabled, the CHW bypass valve loop shall be biased to start with the valve 100 % open.
- For any other plants: When any primary CHW pump is proven on, the CHW bypass valve control loop is enabled. The valve is opened 100 % otherwise. When enabled, the CHW bypass valve loop shall be biased to start with the valve 100 % open.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | have_heaWat | Set to true for plants that provide HW | |
| Boolean | have_chiWat | Set to true for plants that provide CHW | |
| Boolean | have_pumChiWatPri | Set to true for plants with separate primary CHW pumps | |
| Boolean | have_valInlIso | Set to true to enable control loop based on inlet isolation valve command | |
| Boolean | have_valOutIso | Set to true to enable control loop based on outlet isolation valve command | |
| Real | VHeaWat_flow_nominal[nEqu] | Design HW flow rate – Each unit [m3/s] | |
| Real | VHeaWat_flow_min[nEqu] | Minimum HW flow rate – Each unit [m3/s] | |
| Real | VChiWat_flow_nominal[nEqu] | Design CHW flow rate – Each unit [m3/s] | |
| Real | VChiWat_flow_min[nEqu] | Minimum CHW flow rate – Each unit [m3/s] | |
| Real | k | 1 | Gain of controller |
| Time | Ti | 0.5 | Time constant of integrator block [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | VChiWatPri_flow | Primary CHW volume flow rate [m3/s] |
| input RealInput | VHeaWatPri_flow | Primary HW volume flow rate [m3/s] |
| input BooleanInput | u1PumHeaWatPri_actual[nEnaHeaWat] | Primary HW pump status |
| input BooleanInput | u1ValHeaWatInlIso[nEnaHeaWat] | Equipment inlet HW isolation valve command |
| input BooleanInput | u1ValHeaWatOutIso[nEnaHeaWat] | Equipment outlet HW isolation valve command |
| output RealOutput | yValHeaWatMinByp | HW minimum flow bypass valve command [1] |
| input BooleanInput | u1Equ[nEqu] | Equipment enable command |
| output RealOutput | VHeaWatPriSet_flow | Primary HW flow setpoint [m3/s] |
| input BooleanInput | u1HeaEqu[nEqu] | Equipment heating/cooling mode command |
| input BooleanInput | u1PumChiWatPri_actual[nEnaChiWat] | Primary CHW pump status |
| input BooleanInput | u1ValChiWatInlIso[nEnaChiWat] | Equipment inlet CHW isolation valve command |
| input BooleanInput | u1ValChiWatOutIso[nEnaChiWat] | Equipment uutlet CHW isolation valve command |
| output RealOutput | yValChiWatMinByp | CHW minimum flow bypass valve command [1] |
| output RealOutput | VChiWatPriSet_flow | Primary CHW flow setpoint [m3/s] |
Modelica definition
block ControllerDualMode
"CHW and/or HW minimum flow bypass valve controller"
parameter Boolean have_heaWat
"Set to true for plants that provide HW";
parameter Boolean have_chiWat
"Set to true for plants that provide CHW";
parameter Boolean have_pumChiWatPri(
start=not have_heaWat)
"Set to true for plants with separate primary CHW pumps";
parameter Boolean have_valInlIso
"Set to true to enable control loop based on inlet isolation valve command";
parameter Boolean have_valOutIso
"Set to true to enable control loop based on outlet isolation valve command";
parameter Integer nEqu=0
"Number of plant equipment";
parameter Integer nEnaHeaWat=0
"Number of enable signals for HW loop – Valve command or pump status";
parameter Integer nEnaChiWat=nEnaChiWat
"Number of enable signals for CHW loop – Valve command or pump status";
parameter Real VHeaWat_flow_nominal[nEqu](
start=fill(0, nEqu),
unit=fill("m3/s", nEqu))
"Design HW flow rate – Each unit";
parameter Real VHeaWat_flow_min[nEqu](
start=fill(0, nEqu),
unit=fill("m3/s", nEqu))
"Minimum HW flow rate – Each unit";
parameter Real VChiWat_flow_nominal[nEqu](
start=fill(0, nEqu),
unit=fill("m3/s", nEqu))
"Design CHW flow rate – Each unit";
parameter Real VChiWat_flow_min[nEqu](
start=fill(0, nEqu),
unit=fill("m3/s", nEqu))
"Minimum CHW flow rate – Each unit";
parameter Real k(
min=0)=1
"Gain of controller";
parameter Modelica.Units.SI.Time Ti(
min=Buildings.Controls.OBC.CDL.Constants.small)=0.5
"Time constant of integrator block";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VChiWatPri_flow(
final unit="m3/s")
if have_chiWat
"Primary CHW volume flow rate";
Buildings.Controls.OBC.CDL.Interfaces.RealInput VHeaWatPri_flow(
final unit="m3/s")
if have_heaWat
"Primary HW volume flow rate";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1PumHeaWatPri_actual[nEnaHeaWat]
if have_heaWat and not(have_valInlIso or have_valOutIso)
"Primary HW pump status";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1ValHeaWatInlIso[nEnaHeaWat]
if have_heaWat and have_valInlIso
"Equipment inlet HW isolation valve command";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1ValHeaWatOutIso[nEnaHeaWat]
if have_heaWat and have_valOutIso
"Equipment outlet HW isolation valve command";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yValHeaWatMinByp(
final unit="1")
if have_heaWat
"HW minimum flow bypass valve command";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1Equ[nEqu]
"Equipment enable command";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput VHeaWatPriSet_flow(
final unit="m3/s")
if have_heaWat
"Primary HW flow setpoint";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1HeaEqu[nEqu]
if have_heaWat and have_chiWat
"Equipment heating/cooling mode command";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1PumChiWatPri_actual[nEnaChiWat]
if have_chiWat and have_pumChiWatPri and not have_valInlIso and not have_valOutIso
"Primary CHW pump status";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1ValChiWatInlIso[nEnaChiWat]
if have_chiWat and have_valInlIso
"Equipment inlet CHW isolation valve command";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1ValChiWatOutIso[nEnaChiWat]
if have_chiWat and have_valOutIso
"Equipment uutlet CHW isolation valve command";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput yValChiWatMinByp(
final unit="1")
if have_chiWat
"CHW minimum flow bypass valve command";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput VChiWatPriSet_flow(
final unit="m3/s")
if have_chiWat
"Primary CHW flow setpoint";
Controller ctlFloMinHeaWat(
final have_valInlIso=have_valInlIso,
final have_valOutIso=have_valOutIso,
final V_flow_nominal=VHeaWat_flow_nominal,
final V_flow_min=VHeaWat_flow_min,
final k=k,
final Ti=Ti,
final nEqu=nEqu,
final nEna=nEnaHeaWat)
if have_heaWat
"HW minimum flow control";
Controller ctlFloMinChiWat(
final have_valInlIso=have_valInlIso,
final have_valOutIso=have_valOutIso,
final V_flow_nominal=VChiWat_flow_nominal,
final V_flow_min=VChiWat_flow_min,
final k=k,
final Ti=Ti,
final nEqu=nEqu,
final nEna=nEnaChiWat)
if have_chiWat
"CHW minimum flow control";
Utilities.PlaceholderLogical phHeaCoo[nEqu](
each final have_inp=have_heaWat and have_chiWat,
each final have_inpPh=false,
each final u_internal=have_heaWat)
"Placeholder signal for single mode applications";
Buildings.Controls.OBC.CDL.Logical.Not u1Coo[nEqu]
"True if cooling mode";
Buildings.Controls.OBC.CDL.Logical.And onAndHea[nEqu]
if have_heaWat
"True if commanded on in heating mode";
Buildings.Controls.OBC.CDL.Logical.And onAndCoo[nEqu]
if have_chiWat
"True if commanded on in cooling mode";
Utilities.PlaceholderLogical phPumChiWatPri[nEnaChiWat](
each final have_inp=have_heaWat and have_chiWat and not have_pumChiWatPri,
each final have_inpPh=true)
if have_chiWat and not(have_valInlIso or have_valOutIso)
"Use CHW pump signal in case the plant does not have common CHW and HW dedicated pumps";
Buildings.Controls.OBC.CDL.Logical.And pumOnAndCoo[nEqu]
if have_heaWat and have_chiWat and not have_pumChiWatPri and not(have_valInlIso
or have_valOutIso)
"True if pump proven on and equipment in cooling mode – Case with common CHW and HW dedicated pumps";
Buildings.Controls.OBC.CDL.Logical.And pumOnAndHea[nEqu]
if have_heaWat and have_chiWat and not have_pumChiWatPri and not(have_valInlIso
or have_valOutIso)
"True if pump proven on and equipment in heating mode – Case with common CHW and HW dedicated pumps";
Utilities.PlaceholderLogical phPumHeaWatPri[nEnaHeaWat](
each final have_inp=have_heaWat and have_chiWat and not have_pumChiWatPri,
each final have_inpPh=true)
if have_heaWat and not(have_valInlIso or have_valOutIso)
"Use HW pump signal in case the plant does not have common CHW and HW dedicated pumps";
equation
connect(ctlFloMinHeaWat.y, yValHeaWatMinByp);
connect(ctlFloMinHeaWat.VPriSet_flow, VHeaWatPriSet_flow);
connect(ctlFloMinChiWat.y, yValChiWatMinByp);
connect(ctlFloMinChiWat.VPriSet_flow, VChiWatPriSet_flow);
connect(u1HeaEqu, phHeaCoo.u);
connect(phHeaCoo.y, u1Coo.u);
connect(u1Equ, onAndHea.u1);
connect(onAndHea.y, ctlFloMinHeaWat.u1Equ);
connect(onAndCoo.y, ctlFloMinChiWat.u1Equ);
connect(u1ValHeaWatInlIso, ctlFloMinHeaWat.u1ValInlIso);
connect(u1ValHeaWatOutIso, ctlFloMinHeaWat.u1ValOutIso);
connect(VChiWatPri_flow, ctlFloMinChiWat.VPri_flow);
connect(u1ValChiWatInlIso, ctlFloMinChiWat.u1ValInlIso);
connect(u1ValChiWatOutIso, ctlFloMinChiWat.u1ValOutIso);
connect(VHeaWatPri_flow, ctlFloMinHeaWat.VPri_flow);
connect(u1Equ, onAndCoo.u1);
connect(u1Coo.y, onAndCoo.u2);
connect(phPumChiWatPri.y, ctlFloMinChiWat.u1PumPri_actual);
connect(u1Coo.y, pumOnAndCoo.u1);
connect(u1PumHeaWatPri_actual, pumOnAndCoo.u2);
connect(phHeaCoo.y, onAndHea.u2);
connect(u1PumHeaWatPri_actual, pumOnAndHea.u2);
connect(phHeaCoo.y, pumOnAndHea.u1);
connect(phPumHeaWatPri.y, ctlFloMinHeaWat.u1PumPri_actual);
connect(pumOnAndHea.y, phPumHeaWatPri.u);
connect(u1PumHeaWatPri_actual, phPumHeaWatPri.uPh);
connect(pumOnAndCoo.y, phPumChiWatPri.u);
connect(u1PumChiWatPri_actual, phPumChiWatPri.uPh);
end ControllerDualMode;
Buildings.Templates.Plants.Controls.MinimumFlow.Setpoint
Minimum flow setpoint calculation
Information
The minimum flow setpoint is determined as follows, to provide minimum flow through all operating units.
- For the units commanded on in the stage, calculate the highest ratio of minimum flow rate to design flow rate.
- Calculate the minimum flow setpoint as the highest minimum flow ratio multiplied by the sum of the design flow rates for the operating equipment.
Details
For plants consisting of identical units, the minimum flow setpoint is the minimum flow of each unit multiplied by the number of units enabled in the stage.
If the units have different minimum flow to design flow ratios, just maintaining the sum of the minimum flows will not satisfy the equipment with the highest relative minimum flows. Note that this also requires that equipment be balanced to distribute flow proportional to their design flow.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | V_flow_nominal[:] | Design flow rate – Each unit [m3/s] | |
| Real | V_flow_min[:] | Minimum flow rate – Each unit [m3/s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input BooleanInput | u1[nEqu] | Equipment enable command |
| output RealOutput | VPriSet_flow | Primary flow setpoint [m3/s] |
Modelica definition
block Setpoint
"Minimum flow setpoint calculation"
parameter Integer nEqu(
final min=1)=0
"Number of plant equipment";
parameter Real V_flow_nominal[:](
each final unit="m3/s")
"Design flow rate – Each unit";
parameter Real V_flow_min[:](
each final unit="m3/s")
"Minimum flow rate – Each unit";
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput u1[nEqu]
"Equipment enable command";
Buildings.Controls.OBC.CDL.Interfaces.RealOutput VPriSet_flow(
final unit="m3/s")
"Primary flow setpoint";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant floMin[nEqu](
final k=V_flow_min)
"Minimum flow rate";
Buildings.Controls.OBC.CDL.Conversions.BooleanToReal booToRea[nEqu](
each final realTrue=1,
each final realFalse=0)
"Convert to real signal";
Buildings.Controls.OBC.CDL.Reals.Multiply floMinEna[nEqu]
"Minimum flow for enabled equipment";
Buildings.Controls.OBC.CDL.Reals.Divide ratFloMinEna[nEqu]
"Minimum flow ratio for enabled equipment";
Buildings.Controls.OBC.CDL.Reals.Sources.Constant floDes[nEqu](
final k=V_flow_nominal)
"Design flow rate";
Buildings.Controls.OBC.CDL.Reals.MultiMax maxRatFloMinEna(
nin=nEqu)
"Maximum of minimum flow ratio for enabled equipment";
Buildings.Controls.OBC.CDL.Reals.Multiply floDesEqu[nEqu]
"Design flow for enabled equipment";
Buildings.Controls.OBC.CDL.Reals.MultiSum sumFloDesEna(
nin=nEqu)
"Sum of design flow for enabled equipment";
Buildings.Controls.OBC.CDL.Reals.Multiply floMinSet
"Minimum flow setpoint";
equation
connect(u1, booToRea.u);
connect(booToRea.y, floMinEna.u2);
connect(floMin.y, floMinEna.u1);
connect(floDes.y, ratFloMinEna.u2);
connect(floMinEna.y, ratFloMinEna.u1);
connect(ratFloMinEna.y, maxRatFloMinEna.u);
connect(booToRea.y, floDesEqu.u1);
connect(floDes.y, floDesEqu.u2);
connect(maxRatFloMinEna.y, floMinSet.u1);
connect(floMinSet.y, VPriSet_flow);
connect(floDesEqu.y, sumFloDesEna.u);
connect(sumFloDesEna.y, floMinSet.u2);
end Setpoint;