1. Christopher Price Component Level HVAC Control NIST Project
Seminar Meeting 11/2013
Christopher Price
Component Level HVAC Control
NIST Project

2. Motivation Background Cascaded Control Air Volume Systems
Overview
Motivation
Background
Cascaded Control
Air Volume Systems
Hydronic Radiators
Future Work

3. 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.

4. Motivation
Where I Fit

5. 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

6. 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 AEV’s ability to reject disturbances from pressure and the TEV’s 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 AEV’s are good at rejecting disturbances related to pressure but do not offer SH regulation while TEV’s do control SH but there is a significant time lag due to the position of the bulb.

7. Hybrid Expansion Valve
Background
Hybrid Expansion Valve
(2009) Eliot & Rasmussen: Evaporator Superheat Regulation Via Emulation of Semi-Active Flow Control

8. 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.

9. 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

10. 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

11. 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.

12. Damper Types VAV Systems Parallel Blade Opposed Blade Single Blade
Don’t forget to mention the damper speed restriction somewhere in here!
Parallel Blade
Opposed Blade
Single Blade
2009 ASHRAE Handbook Fundamentals
Arrow United Industries

13. Damper Characteristics
VAV Systems
Damper Characteristics
Parallel Blade
Opposed Blade
2009 ASHRAE Handbook Fundamentals

14. Traditional PID vs. Cascaded Control
VAV Systems
Traditional PID vs. Cascaded Control

15. Simulation Model Damper Model VAV Systems
(2010) Yamakawa: Compensation of Manual Reset for PID Controller

16. VAV Systems – Traditional PID Control
Jump to slide showing the damper characteristics.

17. 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

18. 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

19. Equations Hydronic Radiators Radiator: Room: Valve:
(2013) Tahersima: Analytical Solution for Stability-Performance Dilemma for Hydronic Radiators

20. Motivation Hydronic Radiators
(2013) Tahersima: Analytical Solution for Stability-Performance Dilemma for Hydronic Radiators

21. 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)

22. Questions?