[Paper Review] Generalized Short Circuit Ratio for Multi Power Electronic based Devices Infeed Systems: Defi-nition and Theoretical Analysis

Huanhai Xin, Wei Dong+3 more|arXiv (Cornell University)|Aug 27, 2017

Microgrid Control and Optimization12 references3 citations

TL;DR

This paper introduces the generalized Short Circuit Ratio (gSCR) and operation gSCR (OgSCR) to assess small-signal stability in multi-power electronic device infeed systems (MPEIS), extending conventional SCR by decomposing the system into independent single-infeed equivalents. The proposed metrics effectively quantify AC grid strength and stability margins, validated through simulations showing improved accuracy over traditional methods in complex, multi-infeed environments.

ABSTRACT

Short circuit ratio (SCR) is widely applied to analyze the strength of AC system and the small signal stability for single power elec-tronic based devices infeed systems (SPEISs). However, there still lacking the theory of short circuit ratio applicable for multi power electronic based devices infeed systems (MPEIS), as the complex coupling among multi power electronic devices (PEDs) leads to difficulties in stability analysis. In this regard, this paper firstly proposes a concept named generalized short circuit ratio (gSCR) to measure the strength of connected AC grid in a multi-infeed system from the small signal stability point of view. Generally, the gSCR is physically and mathematically extended from conven-tional SCR by decomposing the multi-infeed system into n inde-pendent single infeed systems. Then the operation gSCR (OgSCR) is proposed based on gSCR in order to take the variation of op-eration point into consideration. The participation factors and sensitivity are analyzed as well. Finally, simulations are conducted to demonstrate the rationality and effectiveness of the defined gSCR and OgSCR.

Motivation & Objective

• To address the lack of a stability-oriented short circuit ratio metric applicable to multi-power electronic device infeed systems (MPEIS).
• To develop a generalized SCR (gSCR) that captures grid strength from a small-signal stability perspective in multi-infeed systems.
• To account for operational point variations by introducing operation gSCR (OgSCR).
• To analyze participation factors and sensitivity to enhance interpretability of the proposed metrics.
• To validate the rationality and effectiveness of gSCR and OgSCR through simulation studies.

Proposed method

• The gSCR is derived by decomposing a multi-infeed system into n independent single-infeed systems, each analyzed using conventional SCR principles.
• Theoretical derivation of gSCR involves modeling the equivalent impedance seen by each power electronic device (PED) in the multi-infeed network.
• OgSCR is formulated by incorporating the operating point variation into the gSCR framework, enabling dynamic assessment of grid strength.
• Participation factors are computed to identify dominant components affecting system stability.
• Sensitivity analysis is performed to evaluate how changes in system parameters affect gSCR and OgSCR values.
• Simulations are conducted on a multi-PED system to verify the proposed metrics under various operating conditions.

Experimental results

Research questions

• RQ1 How can the conventional short circuit ratio (SCR) be generalized to apply to multi-power electronic device infeed systems (MPEIS) with complex device interactions?
• RQ2 What is the theoretical basis for defining a generalized SCR (gSCR) that maintains physical and mathematical consistency in multi-infeed systems?
• RQ3 How does the operation gSCR (OgSCR) improve upon gSCR by accounting for operational point variations in real-time grid conditions?
• RQ4 What role do participation factors and sensitivity play in interpreting the stability implications of gSCR and OgSCR?
• RQ5 To what extent do simulation results confirm the accuracy and effectiveness of gSCR and OgSCR in assessing small-signal stability?

Key findings

• The proposed gSCR provides a theoretically sound and physically interpretable measure of AC grid strength in multi-PED infeed systems.
• gSCR successfully captures the impact of mutual coupling among multiple power electronic devices on system stability.
• OgSCR demonstrates improved responsiveness to operational changes, offering a dynamic metric for real-time stability assessment.
• Participation factor analysis reveals dominant devices and interconnections affecting system oscillatory modes.
• Sensitivity analysis confirms that gSCR and OgSCR are responsive to key system parameters such as equivalent impedance and infeed power levels.
• Simulation results validate that gSCR and OgSCR effectively predict small-signal stability margins, outperforming conventional SCR in multi-infeed scenarios.