PROBE LT: Short and Long Term Energy Market Simulation


PROBE LT is a powerful short and long-term market simulation tool designed for efficient analysis of electricity markets and for production cost calculations. PROBE development started in 2001 with the focus on ISO custom solutions, and refinement continued over 10+ years with the support and co-funding of five US ISOs. The ability to work closely with market design experts at each ISO resulted in detailed modeling and an unparalleled resemblance to production full scale power systems and actual market results.

Many of the sub-versions of PROBE available within ISOs (PROBE DA, PROBE MD, PROBE RTMA, PROBE OA) are rolled into one flexible PROBE LT version. The PROBE LT integrated solution includes several major components:

  • Advanced security constrained unit commitment (SCUC) recognizing very detailed generator models
  • High performance economic dispatch (SCED) algorithms capable to solve problems with thousands of generators, tens of thousands of optimized parameters, and many active binding constraints per each time interval
  • Extensive list of enforced constraints includes branch thermal constraints checked under numerous N-1 contingencies and thousands of flowgates, energy limited and pump storage generators, and ancillary services requirements
  • Non-linear load flow model with marginal loss factors updated iteratively
  • Automated Model Builder application creating hourly load flow models on the fly to account for transmission changes

PROBE utilizes proprietary algorithms that were specifically designed for energy market optimization and do not rely on expensive third-party "MIP black box" solvers. The result is a unique product that solves with extraordinary speed and accuracy while providing unprecedented transparency in commitment and high quality dispatch decisions.

PROBE LT is capable of simulating any individual energy market or performing production cost modeling for any larger combined ISO or non-ISO area, enabling users to perform studies ranging from daily day-ahead market simulation to multi-year planning studies. PROBE LT is available for licensing with or without energy market data.

Note: PowerGEM consultants also use PROBE LT for client consulting studies, to serve clients that want occasional market simulation analyses but may not have frequent enough use to justify licensing the software. If you are interested in our market simulation consulting services, please contact PowerGEM.

PROBE Modeling Capabilities

PROBE LT uses detailed unit modeling including minRun/minDown time, ramping, startup cost/time as the function of unit cooling state, notification time, daily energy limits, and capability to provide several types of ancillary services simultaneously. PROBE allows multi-segment cost curves that may change on an hourly basis if desired.

PROBE LT provides detailed co-optimization of energy and ancillary services including multiple ancillary reserve classes.

PROBE models a variety of financial bids such as price sensitive demand, imports, exports, virtual generation and load, and bilateral up-to-congestion bids. PROBE can also perform phase shifter optimization.

Input data flexibility: Convenient short-cuts are provided to enable extensive, yet simple and flexible, data modifications. PROBE LT allows parameter changes (such as fuel price, generator outages, wind factors, etc), if desired, via a csv-format overrides file at any granularity - hourly, daily, weekly, annual, or any user-defined date range.

PROBE Transmission Model

PROBE LT utilizes a full network model with level of detail as used by ISO production versions. It is consistent to the models widely used in transmission planning and shares many features available within PowerGEM TARA software. The list of PROBE modeling features clearly distinguishing PROBE from other competing products includes:

  • PROBE can directly read any size LF case in Siemens PTI and GE PSLF format including 80,000 bus Eastern Interconnection models
  • PROBE computes branch flow via iterative LF solution accounting for losses and doesn't use the more common approach of simplified flow calculations via linear distribution factors. Distribution factors for potentially binding constraints are computed by PROBE on the fly when built-in contingency analysis identifies transmission constraints as potentially binding.
  • PROBE applies transmission outages on an hourly basis. PROBE will determine on the fly how many models with different topologies will exist in the course of the day/study window. Hourly transmission network outages and changes may be entered in a convenient csv input file.
  • PROBE can perform large scale studies with 10,000+ flowgates. PowerGEM's TARA software can be used to perform flowgate screening and create a flowgate file that can be directly used as an input for PROBE studies.
  • PROBE can perform full N-1 analysis - i.e. check thousands of branch flows for thousands of contingencies as used by ISOs, thus it is not limited to a subset of flowgates.

PROBE Performance and Solution Algorithm

Performance: PROBE's solution speed is much faster than other unit commitment tools, including tools used in DA production by ISOs. While PROBE performance depends on the size of the optimized problem, typically solution time for a single day SCUC for a typical ISO (like PJM or MISO size) is within 1-5 minutes.

While PROBE LT is extremely fast, the software features the ability to achieve even faster performance by spreading large simulations across multiple cores. PROBE's built-in batch mode capability allows to run 365 daily runs using multiple CPU cores in just a few hours.

PROBE was developed using high performance C language using propriety SCUC and high performance dual simplex LP based SCED, extensive use of sparse methods for load flow and N-1 contingency analysis, and various other performance enhancements techniques.

PROBE LT runs on any MS Windows computer with Excel.

PROBE Excel Interface and Reporting

PROBE LT has extensive Excel-based reporting and analysis on every aspect of dispatch, pricing, and power flow solution including:

  • Detailed dispatch, LMPs, binding transmission constraints for each time interval, shadow prices and related data
  • Extensive summary reports providing production cost, revenues, total congestion costs, and much more.
  • Financial analysis by market participants.
  • Many advanced and unique reports such FTR revenues, congestion and FTR allocation by constraints, supply/demand curves, on-demand charts over study windows, pivot table analysis, and many other features
  • Additional functions exist for comparing output between scenarios, and drill-down analysis of any bid or LMP including every binding constraint's precise contribution to LMP.
  • All Flowgate flows over the study window and even full N-1 analysis to report constraints near limit at the final solution state.

All reports can be saved in CSV flat formats and then imported in Excel or any other data base application for follow up analysis

If desired, users may export hourly load flow models in Siemens PSSE or PowerWorld AUX format with updated topology and saved optimal dispatch, for further analysis using other power flow analysis software such as PowerGEM TARA.

Applications and Flexibility

A particular strength of the PROBE LT software is the flexibility to use PROBE for a wide range of study applications. See the "Recent PROBE LT Studies" section for recently-completed simulation studies, which provides additional insight into the wide range of potential applications. PROBE's general market capabilities include:

Day-ahead market simulation: PROBE was originally developed to simulate ISO day-ahead markets, thus making day-ahead simulation one of PROBE LT's greatest strengths. Longer-term analysis through "linked" day-ahead market simulation: PROBE LT may be run through batch mode for multi-day analysis such as a monthly or annual market forecast, with PROBE passing end-of-day conditions from one day to the next. As this is the way markets operate in reality, this study methodology is a favorite among licensees and consulting clients for many studies.

Longer-term analysis through multi-day optimization: PROBE LT provides capability to perform unit commitment and dispatch over multiple days, such as a 168-hour solution time window (or longer) as opposed to linked simulation that binds together daily 24-hour solution time windows. Clients often prefer this capability for better mid-term commitment of generating resources, especially long-start generators.

Future year analysis: PROBE LT can run an entire future year - or years - using either long-term simulation methodology, enabling Planning studies, future market analysis, investment decision analysis, and many other studies.

Customizable: While PROBE LT is typically used "off the shelf" at our clients, PowerGEM has customized PROBE LT for specific client study needs. For discussion of PowerGEM PROBE software customization examples, refer to the "PROBE for ISOs" section of our website.

Modeling Real Time and Multi-Settlement Systems

All US markets utilize a multi-settlement system, and most of the commitment decisions are typically made by the initial DA forward financial market and the Reliability Assessment Commitment (RAC or RUC) runs, while the RT market is primarily a balancing market and can be modeled in PROBE via two -pass execution:

  1. Perform DA forward market simulation using hourly time step that saves final UC as an input to the following RT pass
  2. Perform RT run using sub-hourly user configurable time step

This approach allows comparing results of the DA and RT markets for studies such as forecast error, revenue analysis, and intra-day analysis of RT events. This approach was used in the recent PJM Renewable Integration Study

Available Data

PowerGEM actively maintains market data for use with PROBE LT. Data is available on an individual ISO basis or by larger areas, such as the US Eastern Interconnection. With PROBE LT, it is not necessary for our users to license a database for the entire United States if the client operates or is interested in modeling only one market.

For some ISOs, PowerGEM also has a "future system" database, such as a year 2019 system representation including transmission topology, generator retirements, and new generator additions expected for the future year mapped to CEII data. This enables our clients to easily perform longer-term market and planning studies.

Recent PROBE LT Studies

Below are ongoing PROBE LT applications and recent studies completed using PROBE LT that offer insight into the wide range of software capabilities:

  • On-going monthly and annual congestion forecasts based on updated market conditions. This client required a different natural gas price for every day for every pipeline, which is well within PROBE LT's capabilities.
  • This study is NOT confidential: Evaluate the NYISO market, specifically the West zone, for the year 2023. Understand the reason for Western NY (Zone A) congestion driven price increases and gauge the congestion effect of a full Dunkirk shutdown with reliability based transmission upgrades. Link
  • Northern New Jersey market simulation to evaluate FTR revenues for years 2016-2021: Established a "base case" simulation and ran the future year models to determine project impacts, changes from base case, potential congestion changes, and FTR revenues
  • General daily day-ahead market simulation to assist with development of bidding strategies
  • Generator retirement and replacement analysis: Study impact of coal plant retirements in PJM, from a market perspective. Retire coal plants in market model and replace with varying combinations of renewables + natural gas.
  • Day-ahead market simulation to study the impact of various levels of demand response, and its effectiveness in reducing congestion versus key power plants
  • ISO Planning departments have licensed PROBE LT for long-term, future Planning studies. While they have access to their own fully-customized ISO PROBE versions, PROBE LT has proven valuable to Planning groups for long term studies as they prefer to avoid extensive parameters, features, and real-time data feeds embedded in ISO custom versions. PROBE LT also provides Planning groups flexibility to study areas beyond their own ISO.
  • PJM Renewable Integration Study: Real-time / sub-hourly PROBE LT was used to study real-time market operations under various future renewable generation scenarios. Link
  • A large utility has used PROBE LT for several years to evaluate new market design proposals in their ISO footprint
  • Transmission outage analysis: several ongoing PROBE LT studies, both by licensees and PowerGEM staff on behalf of consulting clients