1. Model Validation for Large Scale PV Plants
WECC REMTF Meeting, June 2014
Ryan Elliott, SNL

2. Context Model validation is required
As part of new equipment model development/adoption
To comply with reliability standards
To increase accuracy and transparency in generator interconnection process
Treatment of PV and Wind in WECC Generating Facility Data, Testing and Model Validation Requirements
Wind & PV plant models must be validated against Reference Data (it can be field measurements, type test, manufacturer reference data)
Validation must address active/reactive power capability, active/reactive power controls, protection for different output conditions (e.g, partial output and full output)

3. Overview
Model validation for large scale PV plants using the 2nd generation generic models developed by the REMTF
NERC MOD standards dictate that validated models must be submitted for all generators 75 MVA and greater
WECC policy is more strict and states that models must be submitted for generators 10 MVA and greater
Must be revalidated every 5 years
Developing MATLAB-based tools to help plant owners comply
The status of 2nd gen PV models for large scale deployments
Thorough testing has been done to develop confidence in the generic models and identify implementation refinements

4. PV Model Structure The value of the modular approach becomes apparent
The plant controller (REPC_A) and converter model (REGC_A) are employed for both wind and PV plants
The electrical control model (REEC_B) is different and slightly simpler for PV

5. One-line Diagram PMU measurements are made at the substation level
The plant controller model takes measurements made at the plant level as inputs
The electrical control model requires local measurements made at the terminal bus (must infer from PMU data)

6. Components of a Validation Tool
Dynamic models that correspond well to commercial tools
Simple equivalent impedance model to reflect PMU measurements to the terminal bus
Parameter fitting algorithm using norm minimization as an objective (must be balanced with engineering judgment)
𝑍 𝑠𝑢𝑏
𝑍 𝑐𝑜𝑙
𝑍 𝑔𝑠𝑢
𝑆 𝑔𝑟𝑖𝑑
𝑆 𝑝𝑣
𝑌 2
𝑌 2

7. Inverter Level Validation Example
Bench test peformed on a 3-phase, 50kW PV inverter in a laboratory environment
Response to a symmetrical 75% voltage deviation
Simulated parameter fit reflects a manually tuned response because development of the validation tool is ongoing

8. Large PV Plant Example
PMU data collected from a transmission-connected PV plant
This fault is not ideal for model validation because of its long duration (greater than 0.5 seconds or 30+ cycles)
While not a perfect fit, it demonstrates the value of using PMU data for model validation

9. PV Electrical Control Model Testing
Designed a set of simulations which tested every possible control configuration for REEC_B (32 modes of operation)
Ran the simulations in both PSLF and MATLAB and compared the results (750+ simulations)
Helped develop confidence in MATLAB-based dynamic model implementation needed for model validation tool
Identified a couple of implementation improvements and worked with commercial software vendors to resolve them

10. Summary
Developing MATLAB-based software tools to enable semi-automated parameter fitting to measured response data
Tools are intended to provide guidance, but results must be verified in the commercial tool of your choice
A “good” parameter set should result in a close match under different disturbance conditions
Provided that the control mode and settings are fixed
Plant-level model validation using PMU measurements is constrained by the quality of the data
Disturbances must be large enough to be clearly discernible from measurement noise and unrelated perturbations
Thank you, questions and/or comments?