1 The 50th IEEE PES T&D Conference and Exposition

Variable Speed Heat Pump (VSHP) Design for

Frequency Regulation through Direct Load Control

Authors: Young-Jin Kim (MIT EECS, powersys@mit.edu),

Prof. Leslie K. Norford, and Prof. James L. Kirtley Jr.

04.17.2014

2 Jin ( MIT EECS, powersys@mit.edu )

(a) No. of High Frequency Excursion Events (b) No. of Low Frequency Excursion Events

Frequency excursion ( f > 60.05 Hz ) or ( f < 59.95 Hz ) due to load variations

1. Introduction : Real-time Frequency Regulation

Grid-connected energy storage resources

: PHEVs (electrical), flywheels (mechanical), or water heaters (thermal)

3 Jin ( MIT EECS, powersys@mit.edu )

2. Direct Load Control (DLC)-enabled Variable Speed Heat Pump

DLC-enabled VSHPs: thermal energy storage for grid frequency regulation

4

2. Direct Load Control (DLC)-enabled Variable Speed Heat Pump

Jin ( MIT EECS, powersys@mit.edu )

5

2-1. Modeling of Variable Speed Heat Pump

Jin ( MIT EECS, powersys@mit.edu )

Steady-state response characteristics of VSHP

(a) Mech. Power and Motor Speed (b) COP and Heat Rate

6

2-1. Modeling of Variable Speed Heat Pump

Jin ( MIT EECS, powersys@mit.edu )

Transient response characteristics of VSHP

(a) Mech. Power and Motor Speed (b) Mech. Power and Temperature

7

2-2. Modeling of Variable Speed Drive (VSD)

Jin ( MIT EECS, powersys@mit.edu )

Step response of VSD-controlled VSHP to ΔPref = 10 W

(a) Input Power

Variation

(b) Shaft Speed

Variation

8 Jin ( MIT EECS, powersys@mit.edu )

2-3. Modeling of Building Room

Experimental building room consisting of test and climate chambers

9

(a)

2-3. Modeling of Building Room

Jin ( MIT EECS, powersys@mit.edu )

Thermal networks using analogy between thermal and electrical systems

(b)

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(a) Heat Pump Power Consumption in Boston Univ. Test Building

(c) Direct load control signals 10/24

3. Case Studies and Simulation Results

Jin ( MIT EECS, powersys@mit.edu )

Commercial building with VSHPs in response to DLC signals

(b) Direct Load Control (DLC)

Signals for VSHP Models

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- Generators (DGs) : S = 25 MVA, Building: S = 0.7 MVA with 25-kW VSHPs

11/24

3. Case Studies and Simulation Results

Jin ( MIT EECS, powersys@mit.edu )

Isolated microgrid with commercial buildings

12 Jin ( MIT EECS, powersys@mit.edu )

3-1. Grid Frequency Regulation Scheme for DLC-enabled VSHPs

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3-2. Simulation Results of VSHPs

Jin ( MIT EECS, powersys@mit.edu )

(a) Input Power Variations (b) Shaft Speed Variations

Adjustment of VSHP power/speed in response to DLC signals

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3-2. Simulation Results of VSHPs

Jin ( MIT EECS, powersys@mit.edu )

VSHPs Operations PHP [kW] QHP [kW] COP

ωT_ref1 DLC-enabled 15.04 68.72 5.62

Conventional 15.07 68.81 5.60

|Diff.| [%] 0.20 0.13 0.36

ωT_ref2 DLC-enabled 17.48 75.96 5.20

Conventional 17.55 76.17 5.18

|Diff.| [%] 0.40 0.28 0.39

5-hour average performance of DLC-enabled VSHPs

15 Jin ( MIT EECS, powersys@mit.edu )

3-3. Simulation Results of Building Rooms

Indoor temperature variations for cooling methods

16 Jin ( MIT EECS, powersys@mit.edu )

3-4. Simulation Results of Microgrid

Improvement of real-time grid frequency regulation

(a) Grid Frequency Deviations (b) DG Output Power Variations

17 Jin ( MIT EECS, powersys@mit.edu )

4. Conclusion

DLC-enabled VSHPs as thermal energy storage resources

1) Objective

- Frequency regulation ancillary service via the input power control of the VSHPs

- Ensuring both building occupant comfort and long-term device performance

2) Device Modeling and Simulation Studies

- Heat pump dynamic model that is simplified for real-time simulation studies,

but still comprehensive to analyze operational characteristics

- Test room model using two different cooling methods based on experimental setup

- Simulation case studies to demonstrate the effectiveness of DLC-enabled VSHPs