1. BPA/GE Load Model Improvements Project
WECC MVWGMeeting
June, 2017
Bill Price
Juan Sanchez-Gasca

2. Load Model Improvements Project
Objectives
Implement several improvements to motor models on an experimental basis
Compare model behavior with lab test results
Make adjustments to models as needed
Recommend changes for application to Composite Load Model
Project Information
Funded by BPA
Implemented in PSLF by GE
Completion by Dec. 31, 2017

3. Task 1 – New 3-phase motor model – MOTORLD
Same electrical equations as MOTOR1
Speed exponent for torque instead of power
Connect to a power-flow load instead of a generator
Delete original undervoltage protection logic used in MOTOR1
Implement protection and control logic based on:
- Contactor:
- Controlled Trip:

4. Task 2: Updates to single-phase AC compressor motor models
Upgrade to LD1PAC model to include new stall voltage versus time delay characteristic
Add protection and control models from LD1PAC to MOTORC single-phase motor model

5. Task 3: Model Validation Testing
Use BPA lab tests of air conditioner compressors and fans, including voltage sags, voltage ramps and off-nominal frequency.
Compare model and test results, adjusting model and model parameters as appropriate.
Prepare model validation report
MOTORLD implemented, including contactor and controlled trip
MOTORC protective tripping functions implemented
LD1PAC – voltage dependent stall time (VDST) added
BPA lab test results received – initial comparison simulations made
Project Status – Tasks 1 & 2 completed

6. Voltage-dependent Stall Time (VDST) implementation
For now, a single curve is hard-coded in LD1PAC:
Invoked when Tstall parameter is set < 0.
if (V < 0.57) then
interpolate value of Tstall
timer = timer + Dt / (Tstall/ 60.)
if (timer >= 1) then stall (i.e. stay in stall mode after V recovery)
Note: Tstall will change as V changes
Voltage (p.u.)
Stall time (cycles)
> 0.57
no permanent stall
0.57 15
0.565 12
0.55 9
0.53 6
<= 0.46 3

7. Motor Controlled Trip (CT) Implementation
V0, V1, V2, T1A, T2A, T1B, T2B and “fraction of motors with CT” are input parameters
If (V < V0) start timer
When timer reaches “fast trip” (red) line, trip a fraction of motor = (dT – T1) / (T2 – T1)
As voltage changes, the operating line (black) will move up or down.
If it moves down, T1 will be smaller, so a larger fraction will be tripped
If it moves up, T1 will increase. Fraction already tripped will stay tripped, but additional tripping will be delayed until (dt – T1) exceeds its earlier value.
Anytime V becomes > V0, the timer is reset. Subsequent excursions below V0 will restart the timer at 0. and, if dT becomes > T1, a fraction of the remaining load will be tripped.
Any fraction that is tripped is never reconnected.