PROBE for ISOs: Customized, Advanced Market Simulation and Analysis


PROBE development started in 2001 with the focus on ISO custom solutions, and refinement continued over 10+ years with the support and funding from 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. PowerGEM customized the PROBE market simulation software for five ISOs (PJM, MISO, ISO-NE, NYISO, and CAISO), working with each ISO individually to implement unique versions of PROBE with the following objectives:

  • Model every intricate detail of each ISO's representative market rules and processes
  • Customize data feeds to use all confidential data that runs day-ahead and real-time markets, and to accommodate each ISO's preferred methodology of connecting data to PROBE
  • Customize the PROBE engine for specific, targeted ISO study and analysis purposes

The PROBE software, in general, is an advanced market simulation tool designed for efficient analysis of electricity markets, utilizing advanced security constrained unit commitment and economic dispatch algorithms to arrive at a least-cost solution and set energy market LMPs. PROBE's proprietary algorithms are specifically designed for energy market optimization and do not rely on expensive third-party "black box" solvers. The result is a unique product that solves with extraordinary speed and accuracy while providing unprecedented transparency in commitment and dispatch decisions.

PROBE's main ISOs applications are described in further detail below. Additional customization for some ISO clients has resulted in combination of multiple modules for highly-specific market analysis or market operations purposes, and is typically used by several groups throughout each ISO.

PowerGEM continues actively working with several ISOs on PROBE customization to follow continuously evolving market rules and needs.

PROBE DA / Day Ahead Market

The PROBE software is first and foremost a robust day-ahead market simulator, and each client ISO initially implemented PROBE for this purpose. "PROBE for ISOs" is customized to all day-ahead market rules and data feeds; when a new market rule is implemented at a client ISO, it is often implemented in PROBE at the same time. This extremely detailed customization, along with PROBE's strength in unit commitment and production cost minimization, has resulted in its use not only as a day-ahead "what-if" scenario simulation tool, but as an integral part of the day-ahead market clearing mechanism at some ISOs, with one of largest ISOs running PROBE DA daily since 2005.

Advanced modeling features include:

  • PROBE provides detailed co-optimization of energy and ancillary services including multiple reserve classes and locational reserve enforcements;
  • Full transmission model using either EMS-based node-breaker models (including EMS contingency modeling) or bus- branch based PSSE models; conventional N-1 contingency analysis with no limit on number of monitored elements;
  • Modeling of commercial flowgates used for inter-ISO coordination
  • Integrated losses modeling; detailed generator unit operating characteristics;
  • Modeling of market products such as demand response, virtual trading, bilateral transactions, FTRs, and penalty pricing. Essentially, whatever is optimized in each ISO's day-ahead market is also optimized in PROBE, according to the same rules.
  • Pump storage optimization, limited energy generation, and minimum online capacity constraints
  • On-the-fly model building: Hourly transmission network changes may be entered in a convenient csv input file and new hourly load flow models will be built on the fly.
  • If desired, users may export resulting hourly load flow models in PSSE or AUX format with updated topology and saved dispatch, for further analysis using other power-flow software products.

Performance: PROBE's solution speed has consistently been much faster than other unit commitment tools, including tools used in DA production by ISOs. While PROBE is extremely fast, the software features the ability to achieve even faster performance by spreading large simulations across multiple cores to run multiple days or scenarios.

Reporting: PROBE has extensive Excel-based reporting and analysis on every aspect of dispatch, pricing, and powerflow solution, including dispatch, LMPs, binding transmission constraints, shadow prices, FTRs, production cost, revenues, total congestion costs, and much more. Additional functions exist for comparing output between scenarios, on-demand charts, and drill-down analysis of any bid or LMP including every binding constraint's precise contribution to LMP.

PROBE RAC / Reliability Assessment Commitment

The PROBE RAC software is used for the reliability commitment processes that are typically a part of each ISO's overall market operations mechanism. Three ISOs are currently using some customized form of PROBE RAC.

PROBE RAC typically starts from DA approved commitment. The RAC objective is to commit additional generation to assure reliable next day grid operation, while minimizing incremental start up and no load costs.

PROBE RTMA / Real-time Market Analyzer

Over the last 10-20 years, significant efforts have been made to improve market-based grid dispatching, but the means to measure and analyze the overall dispatching efficiency has lagged. With this reality in mind, PowerGEM developed the PROBE RTMA - Real-time Market Analyzer - that enables market performance measurement, analysis, and feedback, as well as real-time market simulation.

The most notable implementation of PROBE RTMA is the Perfect Dispatch initiative at PJM. The PJM Perfect Dispatch idea was to find the baseline (perfect) optimal solution and quantify the actual market's distance from the baseline. The feedback from the software is used to learn about causes of divergence from the baseline, identify opportunities for market improvement, and incentivize cost-effective dispatch. As of January 2016, PJM reported that Perfect Dispatch has achieved over $1.17 billion saving for PJM customers. The Perfect Dispatch / PROBE RTMA efforts have been recognized as FERC as a ground-breaking software implementation.

For more information check PJM Operations Report (slides 13-18)

There have been several "spin-offs" to this particular application, including a more general day-ahead to real-time market simulator for "what-if" analysis, i.e. the ability to pass day-ahead commitment to real-time and compare results of two markets for studies such as forecast error, revenue analysis, and intra-day analysis of RT events. Much of this capability has been successfully replicated in PowerGEM's PROBE LT version that is available to non-ISO users.

More information about PowerGEM PJM Perfect Dispatch implementation can be found here:


"Perfect Dispatch" - as the Measure of PJM Real Time Grid Operational Performance
Boris Gisin, Qun Gu, James V. Mitsche, Simon Tam, Hong Chen. IEEE Summer Meeting, 2010

PJM Perfect Dispatch Implementation Experience
Presented at FERC Technical Conference On Unit Commitment Experience, June 2010

PROBE OA / Outage Analyzer

The ability to perform economic evaluation of transmission and generation outages has become PROBE's fastest growing application, both within ISOs and at non-ISO PROBE LT clients. While ISO PROBE and PROBE LT may be easily used off-the-shelf for outage impact analysis, the specific PROBE OA software available to ISOs is essentially each ISO's version of PROBE DA, customized to enable automated processes for daily, weekly, monthly, or annual outage analysis.

An overview of a PROBE OA implementation at ISO-New England is available at the following link:

PROBE MD / Multi-Day Optimization

PROBE MD performs unit commitment and dispatch over multiple days, such as a 168-hour solution time window, or longer. This general feature is available in custom ISO versions and applied for purposes such as better optimization of limited energy generation resources and commitment of long-start generators. PowerGEM teamed with one ISO to combine the PROBE MD and PROBE RAC versions for a customized multi-day reliability optimization focused on commitment of the long lead units which can't be properly optimized in DA The multi-day optimization feature is also available in the PROBE LT version.