VSC-Penetrated Grid Strength Evaluation Using Voltage Stiffness
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Solution Overview
Problem
Existing methods for evaluating the voltage strength of voltage source converter (VSC)-penetrated power systems, such as short-circuit ratio, fail to accurately account for the voltage support effect of VSCs, especially as the proportion of renewable energy increases, necessitating a more suitable evaluation method.
Innovation Solution
A method and system for evaluating VSC-penetrated power grids based on voltage stiffness, involving the calculation of voltage stiffness through admittance matrices and Thevenin equivalent impedance, which considers the characteristic differences between VSCs and synchronous generators, facilitating easy implementation in practical engineering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional short-circuit ratio is used to evaluate voltage strength, then the evaluation method is simple and widely applicable, but it fails to accurately reflect the voltage support effect of VSCs due to their current limitation characteristics
Solution Approach 1:
The patent changes the evaluation parameter from short-circuit current-based metrics to voltage stiffness-based metrics. Specifically, it introduces voltage stiffness Kvg as a new parameter that directly characterizes the VSC's voltage support capability, transforming the evaluation approach to align with the actual operational characteristics of VSCs rather than relying on synchronous generator-based assumptions
Solution Approach 2:
The patent uses Thevenin equivalent impedance as an intermediary to bridge the gap between complex power system analysis and practical evaluation. By calculating the Thevenin equivalent impedance of the external system and combining it with VSC parameters, the method creates a simplified yet accurate representation that captures voltage support effects without requiring full system complexity
2Reliability
If generalized short-circuit ratio based on singular-induced bifurcation theory is used, then the theoretical foundation is improved, but the derivation process becomes complex and practicality is limited
Solution Approach 1:
The patent extracts the essential elements needed for voltage strength evaluation from the complex generalized short-circuit ratio theory. Instead of using the full bifurcation theory framework, it isolates and utilizes only the critical relationship between Thevenin equivalent impedance and voltage stiffness, removing unnecessary theoretical complexity while preserving evaluation accuracy
Solution Approach 2:
The patent inverts the traditional approach by not starting from short-circuit current analysis and then trying to adapt it for VSCs, but rather starting directly from voltage stiffness characteristics and working backward to develop the evaluation methodology. This reverse engineering approach simplifies the derivation process while maintaining theoretical rigor
3Adaptability or versatility
If short-circuit ratio is used for evaluation, then the method works well for synchronous generator-dominated systems, but its applicability decreases with increasing VSC penetration rate
Solution Approach 1:
The patent develops a universal evaluation methodology based on voltage stiffness that can accurately assess voltage strength regardless of the mix of synchronous generators and VSCs in the system. The approach using Thevenin equivalent impedance and voltage stiffness Kvg is applicable to both traditional synchronous generator systems and modern inverter-dominated systems, making it universally adaptable to changing grid compositions
Data Source
AI summary
A method and system for evaluating strength of a voltage source converter (VSC)-penetrated power grid based on voltage stiffness are provided. First data corresponding to a to-be-analyzed power grid is acquired in real time, and processed to generate a first admittance matrix corresponding to the to-be-analyzed power grid. The first admittance matrix is processed to generate device impedance data of each VSC and a second admittance matrix corresponding to the to-be-analyzed power grid. Rows and columns where a grid-forming VSC node and a rated alternating-current (AC) bus voltage grid-following VSC node are located are removed from the second admittance matrix to generate a third admittance matrix, which is processed to generate second data and third data corresponding to the VSC node. Strength evaluation data corresponding to the to-be-analyzed power grid is generated based on the third data in combination with the second data.