GridLAB-D – Dynamic Simulation Capabilities PNNL-SA-131557 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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Deltamode-related questions Further Information Deltamode-related questions Contact Frank Tuffner francis.tuffner@pnnl.gov 206-528-3124 GitHub Links https://github.com/gridlab-d/gridlab-d Wiki http://gridlab-d.shoutwiki.com/wiki/Main_Page SourceForge Forums https://sourceforge.net/p/gridlab-d/discussion January 24, 2018