1. Production Cost Modeling Data Work Group
System Data Work Group Meeting PDWG Update, Addressing Power Flow & PCM Differences
Jamie Austin
Production Cost Modeling Data Work Group
(PDWG) – Chair
January 24, 2018

2. Overview (11:45 – 12:00)
Presentation on the Production Cost Model (PCM) and GridView Software.
Propose a few areas where the PDWG and the SDWG can work together to improve the two models, PCM and Power Flow (PF).

3. GridView (Production Cost Modeling Software by ABB)
Simulate security-constrained unit commitment and economic dispatch in large-scale transmission networks

4. What is GridView? GridView Program is
A linear Programming/Mixed Integer Programming-based, Security Constrained, Unit Commitment and Economic Dispatch program
Detailed models for generation and transmission
Simulate hourly and sub-hourly dispatches, typically for a year
Transmission System Planning and Operation Simulation tool
GridView Program does NOT
Solve for AC Power Flow solution (like PSS/E or PSLF)
Calculate Voltage Magnitude ( ≈ 1p.u.)
Calculate reactive power flow, voltage stability
Design for distribution system with three phase separated

5. Key Features related to Transmission Modeling
GridView updates Generation Shift Factor (GSF) if topology changes
DC power flow in GridView is close to real power flow in AC Power Flow
Chronological unit commitment and economic dispatch that takes the normal as well as contingency limits of lines, interfaces and nomograms into account.
Seamless data exchange with PSS/E and PSLF loadflow program.
Marginal loss model that takes the effect of transmission losses into unit commitment and economic dispatch.
Phase angle regulators (PARs) and high voltage DC lines (HVDC) can be modeled and PAR angle and HVDC flow can be exported hourly.
Allows for the modeling scheduled transmission maintenance / outages.

6. GridView Dispatch GridView Mimics Market/Utility Operations
System wide optimization to minimize production cost to serve loads
Transmission constraints – normal and contingency conditions
The various generation limits and operation nomograms
Operating Reserves – spinning, regulation, load following reserves
Determines the startup, shutdown schedules and economic dispatch
GridView can answer the following questions
Economic benefits for transmission projects
Operational impacts from wind / solar projects
Wind/Solar Curtailments
Congestion analysis and Congestion Revenue Right (CRR) evaluation
Loss of Load Expectation (LOLE) calculation
Market structure benefits

7. Transmission Planning
FERC Order 890: Nine Transmission Planning Principles
Economic Planning Studies
FERC Order 1000: Cost Allocation Studies
Three Major Transmission Planning Drivers:
Reliability
Economic
Public Policy

8. Power System Studies PF (PSLF, PSSE) – Operation Reliability
PCM (e.g., GridView) –
Economic Operation
Power Flow Analysis
System Impact Assessment
Voltage & Transient Stability
Reliability Compliance
Reactive Compensation Study
Retirement Study
Path Rating Study
Congestion Revenue Right & LMP Forecasting
Market Structure
Ancillary Services
Public Policy
Congestion Analysis
Cost Benefit Analysis
Renewable Integration study

9. Indicator of System Stress
PCM Output
Indicator of System Stress
Energy Not Served
Insufficient resource adequacy and/or operational flexibility
Hydro Spill, Dump Power, Negative LMPs
Over-generation conditions
Reserve and/or ramping violations
High transmission congestion (U99, U90, U70)
Indicator of load-supply-transmission imbalance
High levels/volatility of imports/exports
Infeasible levels of inter-regional dependency
Excessive cycling of thermal units
Reliability of units may be compromised and insufficient operational flexibility
High RE Penetration/minimum thermal commitment
Dependence on inverter-based resources for voltage, inertia, frequency response, stability

10. Round Trip

11. Round Trip Process
The round trip is a shorthand nickname for a process that facilitates and expedited transfer of power system data and information between power system planning models–the Power Flow model (PF) and the Production Cost Model (PCM).
The round trip process is the first step to better coordinate data exchange between the PF and PCM models and facilitates quick transfer of the results from one model to the other.

12. Export Power Flow Case Based on GridView Simulation
Generator – update dispatch
Load – update real power load, adjust reactive load proportionally
Transmission (line & transformer) – update status
HVDC – update schedule
Data will be copied from the reference case
Bus
Shunt
Controlled Shunt
Area / Zone
Interface
Transaction
Owner
Transformer Impedance Adjustment

13. Why the “Round Trip”? Process attributes:
Having common data and assumptions allows planners to use both models (PCM and PF) to address transmission planning issues that cannot be dealt with using only one of the programs, such as:
loss of inertia, and
assessment of operating flexibility concerns that come with retiring generating plants.
Process attributes:
better data management,
automated exchange capability, and
data consistency between models

14. ADS Cases (PF & PCM)
The goal is to have a common starting point for PCM and PF datasets produced by WECC and the Western Planning Regions
The ADS provides a dataset that is intended to be a common starting point for WPR Transmission Planning Studies. It may be used by WECC and stakeholders to conduct PCM studies and coordinated PF/dynamic studies.
The “2026 ADS Seed Cases” produced by the WPR is the starting point for the 2028 ADS Cases

15. “Round Trip” Data Processing
For the round trip process to work smoothly, the data for the two models must have:
consistent identification (in PF - bus numbers, ckt ID)
representation compatibility
consistent ancillary information data files (transfer limits, cost ranking, other operating limits)
compatible assumptions
Changes to data needs must be properly accounted for in both models; it is best to apply all system topology changes in the power flow.

16. Areas of Potential Improvements

17. Process Automation Sponsored by NTTG
NTTG engaged ABB to improved the data handling capabilities of Gridview:
Fully allow associating multiple powerflow generators to one PCM generator (Many-to-One).
Required more in-depth checking during import. Gridview has two generator tables, both needed to be checked prior to creating a new PCM generator.
Required the aggregation of the “many” PCM generators to a single powerflow generator on export (One-to-Many)
During importing branches and generators, circuit and generator IDs with leading zero’s (“01”) were being converted to “1”.
Code was changed to not strip the “0” and the database was updated to restore the correct ID

18. Process Automation Sponsored by WPRs
The WPRs engaged ABB to improved the data handling capabilities of Gridview:
Bus names were being truncated to 8 characters.
Bus types were being altered:
Bus type = 0, 1, & 2
Code now exports the powerflow bus type
Bus nominal voltages were exported to 2 significant digits.
Code now exports 3 significant digits
Some DC line Rectifiers mode were being changed.

19. Power Flow /PCM Remaining Differences
Differences that warrant reconciliation:
Station Service
Pmin\Pmax
The modeling of Distributed Generation(e.g., BTM-PV)
Netted Generation/Negative Loads
Pumping/Motor Loads
Distributed Resources
DC modeling, back to back, cross-bay, etc.

20. Addressing Differences

21. Station Service (SS)
PF – Data preparation manual, page 23, under Loads: “…SS load>1 MW shall be modeled explicitly…shall have ID set to SS.”
Issue: not all utilities use “SS” for ID
PCM – Currently, PCM doesn’t model SS (SS is netted from Pmax, total unit generation capacity).
Other Considerations:
The “SS” load value is dependent on a number of factors, when considering the 8760 hours dispatch (e.g., PCM dispatch):
The number of units in service
The dispatch level of the units
SS load value may change by season

22. Managing “SS” Differences
Short term solution
Model SS as standalone, consistent with PF modeling
Using unit “gross” capacity for Pmax in PCM will require recalculating the Heat Rate (HR) curves that are currently configured using gross generating capacity, net SS.
Round-Trip PF: Should we turn SS on if associated generator is committed?
SDWG can help with identifying all SS Loads, including those that are using other than “SS” for load ID.
Long term solution
Model SS dynamically to reflect hour-to-hour changes in unit commitment and generating levels
SDWG can help by collecting SS operating definition for each SS load, from which a pattern can be formulated and an equation can be written.
Work with ABB to integrate the equation in GridView

23. Pmax Interim representation, Pmax =gross gen vs. Pmax=gross gen, net SS
Short Term Solution
Process out SS load in PCM (Turn off); Pmax= gross unit rating net SS.
Round-Trip PF: model SS load as non-conforming load (constant) and Pmax = gross unit rating. This requires recalculating the Heat Rate curves.
Long Term Solution
The goal is to have consistent values for Pmax in both databases, PCM and PF.
Add capability in GridView to manage SS load differences, hence, use the same table for Pmax.

24. Behind the Meter-Distributed Generation (BTM-DG) Modeled: on demand side in PF & on supply side in PCM
Three different approaches for modeling BTM-DG in PCM
PCM – Model as an equivalent generator at a specific bus with a unique hourly profile that is different than that for the load
PF – treat as a generator on the load bus; seamless transition with “round trip”
PCM - Model as an equivalent generator at locations with user specific weight
PF – treat as multiple generators at these locations based on weight distributed
“round trip” can manage “many to one”
PCM – Model as a generator with load weighted distributed in an area
PF – Subtract from load forecast and
then distributed to load buses by
load weight
Composite Load model – CMPLDWG
For dynamic study only.
Not for steady state power flow analysis
Do not affect the load model in PSSE
and PSLF
Pdg is netted to demand Pload

25. Negative Generation
The California Energy Commission (CEC) staff reviewed hourly historic data for utility scale PV plants and observed negative reported values for many plants (during non-daylight hours).  It was determined these negative values represented electric consumption by the power plant when it was not generating. 
The CEC Demand Office staff recommended that we not include these negative values in the production cost model since this was load already captured in the CEC’s demand forecast. However, negative values may not be captured in the PF case. Can this be verified by SDWG?

26. Pumping/Motor Loads/Distributed Resources
Pumps
PCM:
Irrigational pumps loads (Delta, Buena Vista, Wheeler Ridge, Windgap, Edmondton and others) are backed out from the load forecast and are modeled as generators with negative output. Irrigation pumps have output shapes according to the historical data
Note: this is done because the irrigation shapes are different from the load shapes.   
Pump-storage power plants (Helms, Castaic) are modeled as dispatchable generation/load.
PF:
Irrigational pumps are modeled as generators with negative output, with the exception of the Tracy pumps that are modeled as load.
Distributed Resources (DR)
Distributed Resources are modeled as generators with hourly profiles
Distributed Resources are not modeled in PF, but these do amount to a sizable block of energy. Not having DR in PF causes a mismatch with the “round trip”.

27. DC Modeling, Trans-Bay Cable
The Trans-Bay Cable, which is located under the San Francisco Bay, is a high voltage DC line that uses voltage-source converter (VSC) technology.
PCM:
Trans-Bay Cable is modeled as a DC line.
PF:
it is modeled as two generators: one at the source (Pittsburg substation) with negative output, and one at the sink (Potrero substation) with positive output.
Losses in the DC line are also considered, thus the generator at the Potrero Substation has smaller positive output, than the generator at Pittsburg that has larger negative output.
In dynamic stability, Trans-Bay cable is modeled with a user-written model which is linked to the generators modeled in power flow.
The difference in the modeling of the Trans-Bay Cable in the power flow and production cost models may cause additional challenges with the “round trip” when the PCM case is converted into a power flow case.