Online Voltage Stability Assessment for Load Areas Based on the Holomorphic Embedding Method

TL;DR

This paper introduces a non-iterative, online voltage stability assessment method using holomorphic embedding to accurately evaluate load bus stability margins in real-time, considering load variations and external system influences.

Contribution

It develops a novel holomorphic embedding-based approach with a physical germ solution and adaptive Pade approximants for real-time voltage stability assessment.

Findings

Accurately calculates voltage stability margins at load buses.

Demonstrates effectiveness on large-scale power system data.

Provides a non-iterative, computationally efficient solution.

Abstract

This paper proposes an online steady-state voltage stability assessment scheme to evaluate the proximity to voltage collapse at each bus of a load area. Using a non-iterative holomorphic embedding method (HEM) with a proposed physical germ solution, an accurate loading limit at each load bus can be calculated based on online state estimation on the entire load area and a measurement-based equivalent for the external system. The HEM employs a power series to calculate an accurate Power-Voltage (P-V) curve at each load bus and accordingly evaluates the voltage stability margin considering load variations in the next period. An adaptive two-stage Pade approximants method is proposed to improve the convergence of the power series for accurate determination of the nose point on the P-V curve with moderate computational burden. The proposed method is illustrated in detail on a 4-bus test system and then demonstrated on a load area of the Northeast Power Coordinating Council (NPCC) 48-geneartor, 140-bus power system.