Voltage Stability and System Operating Limits

Real-time Voltage Stability Assessment & Enhancement (VSA&E)

Voltage Stability, “the ability to maintain steady voltages at all buses after being subjected to a disturbance”, is essential to the reliability of bulk electric power systems.

Control center operators need to know the limits (in real time) under which the system will perform reliably, especially under these changing conditions. Increased loads and renewable energy will put more and more stress on transmission systems, leading to potential voltage instability.

BSI Voltage Stability Analysis and Enhancement (VSA&E) is a comprehensive software application and BSI’s flagship product used by electric utilities since 2003 to:

  • Evaluate voltage stability by determining dynamic system operating limits and margins in real time, future time, and study mode, all built on patented direct methods.
  • Determine how far the system is from a potential voltage issue in real time - Compute real time power transfer limits and capability based on the system voltage collapse point, bus voltage limits under N-1 conditions, bus voltage drop point limits, and thermal limits.
  • Mitigate instabilities and maximize power transfer without violating limits using the BSI-recommended control adjustments engine – This can include any devices modeled in the system, including capacitor bank switching, load tap changers (LTC), generator reactive outputs, transmission line switching, and more.

    In addition to real time, BSI VSA&E can operate in future time horizons, determining limits and system conditions for the next 30 minutes…to the next 24 hours...to the next 7 days ahead.

Key Functions

  • Contingency Analysis: Patented fast screening and ranking of up to 25,000 contingencies in real time or 100,000 contingencies in planning cases.
  • System operating limits and transfer margin calculated for:
    • Voltage Collapse
    • Voltage Limit Violations
    • Voltage Drops and Deviations
    • Thermal Limit Violations
  • Control Switching for Mitigation: Recommends a set of proactive control adjustments in real time to mitigate contingencies (if implemented)
    • Preventive Control mitigates insecure contingencies
    • Enhancement Control allows users to set a desired power transfer increase (e.g., 200 MW) and the control engine will find the necessary adjustments to achieve the increased power transfer capability.
  • Strong Remedial Action Scheme (RAS) modules
  • Study Mode: Takes any real-time or look-ahead case and brings in a comprehensive study tool to manipulate the model, parameters, and attributes before running further studies.

Key Features

  • Accepts any input format (PSS/e, CIM, PSLF, etc.), allowing for EMS integration capability
  • Parallel design for real-time application with the implementation of a distributed parallel computing platform
  • Modern and intuitive user interface designed in collaboration with long-time control center operators and engineers
  • Over 20 years of field implementation, validation, and development
  • Primary VSA tool for the Western Electric Coordination Council (WECC), USA

Learn more about how electric utilities use BSI Voltage Stability tools in the book "Use of Voltage Stability Assessment and Transient Stability Assessment Tools in Grid Operations" by Sarma Nuthalapati.

Also, visit the IEEE Profile of Professor Chiang to see Published IEEE Papers on Voltage Stability Assessment and Control.