[Paper Review] A Short-Term Voltage Stability Index and case studies

Wenlu Zhao|arXiv (Cornell University)|Feb 22, 2017

Power System Optimization and Stability10 references3 citations

TL;DR

This paper proposes a continuous, quantitative, and multi-dimensional Short-Term Voltage Stability Index (SVSI) to assess voltage stability in large power systems, particularly in the East China Grid. The SVSI evaluates transient voltage restoration, oscillation, and steady-state recovery after faults, validated across 10,000 cases and applied to dynamic VAR allocation optimization.

ABSTRACT

The short-term voltage stability (SVS) problem in large-scale receiving-end power systems is serious due to the increasing load demand, the increasing use of electronically controlled loads and so on. Some serious blackouts are considered to be related to short-term voltage instability. In China, the East China Grid (ECG) is especially vulnerable to short-term voltage instability due the its increasing dependence on power injection from external grids through HVDC links. However, the SVS criteria used in practice are all qualitative and the SVS indices proposed in previous researches are mostly based on the qualitative SVS criteria. So a Short-Term Voltage Stability Index (SVSI), which is continuous, quantitative and multi-dimensional, is proposed in this paper. The SVSI consists of three components, which reflects the transient voltage restoration, the transient voltage oscillation and the steady-state recovery ability of the voltage signal respectively after the contingency has been cleared. The theoretical backgrounds and affected factors of these three components of SVSI are analyzed, together with some feasible applications. The verification of the validity of SVSI are tested through more 10,000 cases based on ECG. Additionally, a simple case of selecting candidate locations to install dynamic var using SVSI is presented to show its feasibility to solve the optimization problem for dynamic var allocation.

Motivation & Objective

• Address the lack of quantitative voltage stability criteria in large-scale receiving-end power systems with high external power injection.
• Overcome limitations of qualitative and non-continuous indices used in practice.
• Develop a multi-dimensional, continuous index that captures transient voltage behavior post-contingency.
• Enable practical applications such as dynamic VAR allocation optimization using the SVSI.
• Validate the index’s effectiveness in real-world system conditions through extensive case studies.

Proposed method

• Propose a three-component SVSI: one for transient voltage restoration, one for transient oscillation, and one for steady-state recovery.
• Formulate the SVSI using time-domain voltage signal analysis after fault clearance.
• Derive theoretical foundations for each SVSI component based on voltage dynamics and system response characteristics.
• Apply the SVSI to a wide range of contingency scenarios in the East China Grid (ECG) to test robustness and sensitivity.
• Use the SVSI to rank buses for dynamic VAR support allocation, demonstrating feasibility in optimization.
• Validate the index using over 10,000 contingency cases to ensure consistency and reliability.

Experimental results

Research questions

• RQ1 How can a continuous, quantitative, and multi-dimensional index be developed to assess short-term voltage stability?
• RQ2 What are the key dynamic components of voltage response that influence short-term voltage stability?
• RQ3 How does the proposed SVSI compare to qualitative criteria in identifying weak voltage points?
• RQ4 Can the SVSI effectively guide the optimal placement of dynamic VAR support devices?
• RQ5 What is the performance of the SVSI across a large number of system contingencies?

Key findings

• The SVSI successfully quantifies short-term voltage stability across 10,000 contingency cases in the East China Grid.
• The index captures transient voltage restoration, oscillation, and steady-state recovery, offering a comprehensive stability assessment.
• The SVSI demonstrates strong correlation with actual system voltage behavior, validating its reliability.
• The index enables effective identification of candidate buses for dynamic VAR support installation.
• The proposed method reduces reliance on qualitative judgment and improves decision-making in voltage stability monitoring.
• The SVSI is applicable to real-time stability assessment and optimization of reactive power compensation.