Load Flow, Contingency Analysis, Voltage Stability and Power Transfer Analysis – Physical and Operational Margins (POM)

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POM is a powerful and highly automated power systems engineering application used for steady-state stability analysis, which includes load flow, AC contingency analysis, power transfer and voltage stability analyses.

The main purpose of POM program is massive automated AC contingency analysis, with hundreds of thousands to millions of contingencies (19 million contingencies is the largest run so to date) being applied within one simulation run. There is no limit on the number of contingencies to be applied within a single run, or the number of buses in a load flow case.

POM fully automates the N-1, N-1-1, N-2 and higher AC contingency analysis tasks. The application reads the existing load flow cases and contingency lists. Preparation of the input files is very simple and massive contingency analysis may be performed by a simple click on the appropriate button.POM simultaneously monitors and enforces voltage constraints, thermal overloads and steady-state stability during the AC contingency analysis. POM performs the AC contingency analysis extremely fast, and prebuilt, multithreading capabilities allow users to further speed up computations.

Run -time example for running AC contingency analysis on an 8000-bus case (after topology processing):

  • 5,758,474 processed contingencies within one simulation run;
  • 49,228 critical contingencies found (e.g., contingencies resulting in one of the constraints being violated);
  • Execution time: 02:46:51.6440713 (~0.00174 sec/contingency or~34,500 contingencies/minute).

During automatic (N-k) contingency analysis a database is created, and any contingency that causes a violation of one or more constraints is recorded, along with data about those violations. This database is later analyzed, providing information regarding the reliability of the existing or planned electric system as modeled. The user can choose to output results as a Microsoft Access or SQLite database.

POM offers the capability to perform very specific, user-defined studies by implementing powerful and flexible scripting. Three scripting languages are available in POM:

  • Microsoft® VB.Net
  • Python
  • C#

Major uses of POM include:

  • Automating NERC-compliance studies:
    • Massive fast N-1, N-1-1, N-2 and higher order AC contingency analysis
    • Any scenario may be automated and simulated
    • Automatic remedial actions when used along with optimal mitigation measures (OPM)
    • Database output and flexible reporting
    • Uses existing contingency lists or generates generic N-1 and N-2 contingency lists
    • Different limits and solution parameters may be set for the N-0, N-1 and N-2 contingencies within the same simulation run
  • Automated AC transfer/contingency analysis with visualization while simultaneously monitoring and enforcing voltage constraints, thermal overloads and steady-state stability:
    • Determines available transfer capability for each contingency
    • Determines interface flows for each contingency at each transfer step
    • Automatically builds PV-curves/QV-curves
  • Reliability analysis
  • Outage coordination

Graphical capabilities of POM

POM allows the user to visually represent the monitored constraints while working in interactive modes. Specific, user-defined graphical output is available when working in script mode.

POM allows to visualize the power flow case through the use of the animated one-line diagrams and geographical maps. All of the graphical power system elements (generators, loads, transmission lines, transformers, etc.) are fully functional and can be switched in and out of service directly from the application screen. Full color, one-line diagrams may be saved in a variety of graphical formats.

Methodology incorporated in POM

The basis of POM is a fast and robust power flow solution algorithm. POM incorporates a nonlinear power system model. Full Newton method is used to solve the nonlinear power flow equations. The contingency screening technique utilizes the full AC analysis. In order to solve the large systems of nonlinear equations, POM incorporates the fast and effective sparse technique.

The concept of physical and operational margins consists of a physical margin and an operational margin. Operational margin is the voltage stability margin. Physical margin incorporates the voltage and thermal limits. POM allows its users to determine the physical and operational margins while applying contingencies. Such margins are an important characteristic of each contingency.

The methodology used for AC contingency analysis has the capability to simultaneously monitor the voltage stability, thermal, voltage and flowgate constraints.

In 2021 the new version POM Core is to be released. It is about 5 time faster than POM Suite.