CMPLDWG Composite Model with Distributed Generation Approval Irina Green Regional Transmission Senior Advisor, California ISO WECC MVWG, January 2018

Background – Composite Load Model CMPLDW Currently, Phase II approved by WECC with single-phase A/C stalling enabled Model parameters updated, DER part not included

DER Portion of Composite Load Model Available in the CMPLDWG model Simplified, few parameters required Contains current limit logic and under- and over-voltage and frequency protection Protection can be modeled according to the PRC-024 Standard

GE PSLF CMPLDWG Model, DER (DG) Part

DER Types (NERC Reliability Guideline) Utility-Scale Distributed Energy Resources (U-DER): directly connected to the distribution bus or through a dedicated, non-load serving feeder. Three-phase and can range in capacity, for example, from 0.5 to 20 MW Retail-Scale Distributed Energy Resources (R-DER): offset customer load. Residential, commercial, and industrial. The residential units single-phase, the commercial and industrial single- or three-phase. Distributed Energy Resources may include: Distributed Generation – in front or behind the meter Energy Efficiency – load modifier embedded in load forecast Demand Response – demand or supply, Energy Storage – can be modeled as aggregated, supply or demand side DER that is a part of composite load model – Behind the meter solar PV

Modeling Behind the Meter DG in Power Flow (GE PSLF) Model calculated amounts of PV at each bus by specifying the P and Q values as separate entries in the power flow load data, including the following : Pdg - MW output of distributed generation Qdg - MVAr of distributed generation (sign convention same as generators) Stdg - DG status (1 – on-line)

Modeling Behind the Meter DG in Dynamic Stability (GE PSLF) Model cmpldwg composite load model with distributed generation DG type – solar PV Initial Pdg method : 0) fraction of P load, 1) in MW, 2) Use P& Q from load table Power factor Current limit, per unit Imax At which voltages and frequencies starts tripping and at which all DG is tripped Fraction of DG that recovers when voltage or frequency recovers Why DER is needed to model as a part of composite load model?

WECC Transmission System Planning Performance Criteria TPL-001-WECC-CRT-3

Need for the Model High penetration of distributed solar PV, thus need to consider their impact Important to have accurate and adequate models Netting DER with load or modeling as generators at transmission buses instead of at the end of the feeders may give less accurate results Due to large amount and numerous locations of DER, modeling them as generators will significantly increase the required amount of data and slow down the simulations Delayed voltage recovery is very sensitive to composite load model parameters, including parameters and especially trip settings for DER The model is available in GE PSLF and PowerWorld Composite load model with DER is used by the California ISO for the last two years

Model Performance and Validation California ISO performed numerous studies with CMPLDWG model within the annual Transmission Plans The model performs as expected and the study results showed reasonable behavior The model cannot be tested directly because it represents not an actual equipment, but its aggregated equivalent Variable nature of load and constant change in DER output doesn’t allow to have meaningful comparison between measurements and simulation DER model represents a small additional block to the composite load model that was previously approved by WECC

2022 Light Spring case, 3-phase fault on 115 kV bus next to load with 22.2 MW DER and 29 MW load, DLO Frequency Voltage

2022 Light Spring case, 3-phase fault on 115 kV bus next to load with 22.2 MW DER and 29 MW load, DLO Distributed Generation Composite Load

Examples of Simulations with and without DG

Proposal It is proposed to approve the CMPLDWG model to use in the WECC dynamic database and in the dynamic stability studies. To be on a conservative side, the trip settings for voltage and frequency are recommended to model in accordance with the NERC PRC-024 standard. Having the DER modeled as a part of the composite load becomes more critical with the higher penetration of the behind-the-meter distributed generation. Other options of modeling these resources give less accurate and less realistic results

Future Work Improve the models of load and distributed generation. Continue to perform system impact and sensitivity studies of the composite load model with DER Develop DER models for generation other that solar PV Compare the simulations with historical events, if data is available Continue work on the new modular models, including DER_A model that will become a plug-in into composite load model, as well as be a stand alone model  

Please send your comments to Irina Green QUESTIONS? COMMENTS? Please send your comments to Irina Green igreen@caiso.com