christopher price component level hvac control nist project
DESCRIPTION
Motivation Background Cascaded Control Air Volume Systems Overview Motivation Background Cascaded Control Air Volume Systems Hydronic Radiators Future WorkTRANSCRIPT
Christopher Price Component Level HVAC Control NIST
Project
Seminar Meeting 11/2013 Christopher Price Component Level HVAC
Control NIST Project Motivation Background Cascaded Control Air
Volume Systems
Overview Motivation Background Cascaded Control Air Volume Systems
Hydronic Radiators Future Work DMPC Control Project (NIST)
Motivation DMPC Control Project (NIST) Advanced control algorithms
to generate system set points Reduced energy consumption and cost
through improved efficiency Full energy savings when components
have adequate tracking Research is under the NIST project which is
the DMPC for Building Energy Systems umbrella. Remind everyone what
the DMPC does, i.e. generates set points for subsystems/individual
components to follow. It is therefore important that those
components provide adequate set point tracking to take full
advantage of the DMPC energy savings potential. Also can provide
ways of increasing actuator/component lifetime by eliminating
common problems with control algorithms. Motivation Where I Fit
Vapor Compression Cycle
Background Vapor Compression Cycle Quickly go though the cycle in
order to explain the purpose of the expansion valve which will lead
into the problem of valve hunting. (2010) Eliot & Rasmussen: On
Reducing Evaporator Superheat Nonlinearity Expansion Valves
Background Automatic Expansion Valve Capillary Tube
Thermostatic Expansion Valve Automatic Expansion Valve Capillary
Tube Explain the development of the controls for the VCC system and
what they are good at controlling. It is the combination of the
AEVs ability to reject disturbances from pressure and the TEVs
ability to regulate SH that could be combined to make the
HEV/Cascaded control loop. Evaporator SH depends on evaporator
pressure, and outlet temperature. So AEVs are good at rejecting
disturbances related to pressure but do not offer SH regulation
while TEVs do control SH but there is a significant time lag due to
the position of the bulb. Hybrid Expansion Valve
Background Hybrid Expansion Valve (2009) Eliot & Rasmussen:
Evaporator Superheat Regulation Via Emulation of Semi-Active Flow
Control Block Diagram Cascaded Control
Explain the construction of this loop. Then explain the
linearization that comes from this construction. (i.e. mass flow
map Km(v) appears in the numerator and denominator) . Also should
point out the G(s) and H(s) part of this. So basically the SH
appears to have been linearized to the slow control loop. Valve
Position to Mass Flow
Cascaded Control Valve Position to Mass Flow Mass Flow to Pressure
Mass Flow to Superheat (2009) Eliot & Rasmussen: Evaporator
Superheat Regulation Via Emulation of Semi-Active Flow Control
Apply same control idea to air handlers Two main types:
Air Volume Systems Apply same control idea to air handlers Two main
types: Constant Volume Systems Flow rate constant, temperature
varied Variable Air Volume Systems* Varied flow rate, temperature
constant VAV Systems Schematic Describe the basic operation of the
VAV system describing the individual components and the operating
principles like fan maintaining constant static pressure and the
damper opening and closing to allow more air through to the space.
Damper Types VAV Systems Parallel Blade Opposed Blade Single
Blade
Dont forget to mention the damper speed restriction somewhere in
here! Parallel Blade Opposed Blade Single Blade 2009 ASHRAE
Handbook Fundamentals Arrow United Industries Damper
Characteristics
VAV Systems Damper Characteristics Parallel Blade Opposed Blade
2009 ASHRAE Handbook Fundamentals Traditional PID vs. Cascaded
Control
VAV Systems Traditional PID vs. Cascaded Control Simulation Model
Damper Model VAV Systems
(2010) Yamakawa: Compensation of Manual Reset for PID Controller
VAV Systems Traditional PID Control
Jump to slide showing the damper characteristics. VAV Systems
Cascaded Control
PID Control Cascaded Control Case MAE RMS 20% 0.4461 0.1239 Low
Flow 0.743 0.263 35% 0.4274 0.1052 Mid Flow 0.351 0.097 50% 0.8246
0.2489 High Flow 0.268 0.047 80% 1.9682 0.5446 The ones with orange
have damper hunting present. Lessons: 1. Have to tune the damper
for lowest expected load condition b/c of hunting behavior 2.
Reduced temperature tracking because of small control gains 3.
Cascaded control loop eliminates the presence of hunting while
improving performance Shown cascaded control works for refrigerant
and air mediums
Hydronic Radiators Shown cascaded control works for refrigerant and
air mediums Apply control design to water radiator systems
Currently working on validating results from Tahersima 2013 paper
Equations Hydronic Radiators Radiator: Room: Valve:
(2013) Tahersima: Analytical Solution for Stability-Performance
Dilemma for Hydronic Radiators Motivation Hydronic Radiators
(2013) Tahersima: Analytical Solution for Stability-Performance
Dilemma for Hydronic Radiators Study the effect of sampling rate on
performance of cascaded loop
Future Work Study the effect of sampling rate on performance of
cascaded loop Proper tuning of cascaded loop control Application of
cascaded control to positive displacement components (fans/pumps)
Alternate control structures (e.g. feed forward control)
Questions?