1. GridLAB-D – Dynamic Simulation Capabilities
PNNL-SA
GridLAB-D – Dynamic Simulation Capabilities
Frank Tuffner
Pacific Northwest National Laboratory
WECC Model Validation Working Group
Salt Lake City, Utah – January 24, 2018
January 24, 2018

2. GridLAB-D: A Unique Tool to Design the Smart Grid
Power Systems
Loads
Markets
Unifies models of the key elements of a smart grid:
Over 55,000 downloads in over 150 countries
Smart grid analyses
field projects
technologies
control strategies
cost/benefits
Time scale: sec. to years
Open source
Contributions from
government
industry
academia
Vendors can add or extract own modules
Open-source, time-series simulation of an operating smart grid, from the substation to individual end- use loads & distributed energy resources, in unprecedented detail
Simultaneously solves 1) power flow, 2) end-use load behavior in tens of thousands of buildings and devices, 3) retail markets, 4) control systems, and 5) electromechanical dynamics.

3. GridLAB-D Capabilities
Performs time-series simulations
Seasonal effects (days to years)
Midterm dynamic behavior (secs to hrs)
System dynamics (milliseconds)
Simulates control system interactions
Device- and system-level controls
Market interactions
Typical Use Cases
Interconnection of distributed generation and storage
New and innovative retail market structures (e.g., DSOs)
Evaluation of demand response and energy efficiency
Volt-VAr optimization and conservation voltage reduction design
Sectionalizing, reconfiguration, automation, and restoration
Microgrids and resiliency
January 24, 2018

4. Definitions for this presentation
Dynamic simulation can include time series (timestep greater than 1 second)
For this presentation, quasi-steady state simulation is defined as having a timestep at 1 second or greater
Sequence of powerflow states coupling other behaviors, such as multi-state load models
Focused typically on 1-minute or longer range – behavioral and diurnal dynamics
For this presentation, dynamic simulation is defined as having a timestep less than 1 second
Sequence of powerflow states coupling differential equations
Focused mainly on 0.5 ms to 50 ms range – electromechanical dynamics
January 24, 2018

5. General “deltamode” capability
Deltamode is the GridLAB-D capability to enable timesteps less than 1 second
GridLAB-D has the ability to transition in and out of this simulation mode
Start simulation in quasi-steady state
Transition into deltamode
Transition back into quasi-steady state
Repeat as necessary
January 24, 2018

6. Dynamic Simulation Usages
Transients on distribution systems
Tripping of IEEE 1547A devices
Grid Friendly Appliance™ impacts
Microgrid Analysis – Resiliency
Inrush and line charging
Overhead and underground lines being energized
Transformer saturation
Motor starting surges
Frequency and voltage impacts
Acceptable ranges
Secondary tripping of items
Evaluate methods for improving resiliency
January 24, 2018

7. Overall Module Support
GridLAB-D modules that have deltamode support in some form
Powerflow (all objects support it, on some level)
Reliability (ability to induce events at subsecond scales)
Generators (diesel generators, inverters, and simple battery/solar)
Residential (house has initial participation, but most models do not support)
January 24, 2018

8. Object models Implemented
Synchronous generation
Inverter-based generation
Line/Load charging
Transformer saturation
Single-phase induction motors
Three-phase induction motors
Variable frequency drives
January 24, 2018

9. Synchronous Generators
Three-phase, unbalanced interfacing
Synchronous machine model
Variety of governors implemented
(None)
DEGOV1
GAST
GGOV1 (two forms)
Constant real power dispatch (PI-controlled)
Several exciter modes
SEXS
Constant reactive power dispatch (PI-controlled)
Terminal voltages for three diesel generators on 123-node test system for a load step change
January 24, 2018

10. Droop mode controls for VSI
Inverters
Three-phase or single-phase interfacing
Use with photovoltaics or energy storage (batteries)
Optional ramp-rate implementations
Optional IEEE 1547/1547A checks, or custom limits
Two primary modes of operation:
Grid following
Constant PQ dispatch
Constant PF mode (PV)
Volt-Var Adjustment/Response (Rule 21)
Load following
Voltage source
Droop-based response (P and Q)
Isochronous operation
Base VSI Controls
Droop mode controls for VSI
January 24, 2018

11. Simple overhead line energization – GridLAB-D and PSCAD results
Line/Load Charging
Model in rush associated with induction/capacitance charging
Inductance field establishment
Line capacitance charging
Impedance-based loads
Ability to translate I-P loads to Z to model
Simple overhead line energization – GridLAB-D and PSCAD results
January 24, 2018

12. Transformer Saturation
Builds off the line/load charging
Models the saturation of the transformer windings
Grounded Wye-Wye supported right now
Transformer current in 8500-node system during connection of primary transformer
Transformer Saturation Curve
Transformer current in 4-node system during transformer connection

13. Single-phase Induction Motors
Attach to primary or secondary voltage systems
Multi-state to capture starting, stalling, and tripping behavior
Most dynamics portions on the dynamic-phasor implementation of: B. Lesieutre, D. Kosterev, and J. Undrill, “Phasor modeling approach for single phase A/C motors,” Proc. of 2008 IEEE PES General Meeting, pp. 1-7, 2008.
Power measurements at a running motor and starting motor on simple 4-node system
January 24, 2018
Motor state during fault on distribution feeder

14. Three-phase Induction Motors
Multi-state to capture starting, stalling, and tripping behavior
Dynamics based on: B. Braconnier, “Dynamic Phasor Modeling of Doubly-Fed Induction Machines Including Saturation Effects of Main Flux Linkage,” M.S. Thesis, Univ. of British Columbia, Sept. 2012
Currently being validated/tested
Three-phase induction motor voltage change simulation in GridLAB-D and PSCAD
January 24, 2018

15. Variable Frequency Drives
Attaches to three-phase systems, at the moment
Simplified AC-DC-AC conversion model
Simplified average-model implementation
Frequency ramping start (constant torque mode)
Constant speed (variable torque mode)
Still being fully validated
Example efficiency table for VFD
VFD hp Rating
Load, Percent of VFD Rated Power Output
1.6
12.5 25 42 50 75
100 3 31 77 86 90 91 93 94 5 35 80 88 92 95 10 41 83 96 20 47 97 30 46 60 51 87 55 89
200 61
400
January 24, 2018

16. Dynamic Simulation – Path Forward
Current research/work
Complete validation of three-phase induction motor model with PSCAD
Investigate single-phase induction motor further
Incorporate further/more detailed protection modeling into motor models
Expand transformer saturation to other types
Validating the transitions in greater detail/testing
Potential future work
More co-simulation ties
Further microgrid-related controls
January 24, 2018

17. Deltamode-related questions
Further Information
Deltamode-related questions
Contact Frank Tuffner
GitHub Links
Wiki
SourceForge Forums
January 24, 2018