Power System Inertia Evaluation via Impedance Response
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Solution Overview
Problem
Current methods for evaluating the inertia and frequency regulation capability of power systems, particularly those dominated by non-synchronous power sources like wind and photovoltaic energy, face challenges in accuracy, data demand, and robustness, especially under normal operation and small disturbances, and fail to effectively account for virtual inertia resources, leading to instability and poor frequency stability.
Innovation Solution
A method and system that inject active power disturbance signals into the power system using non-synchronous power supplies, allowing for the evaluation of inertia and frequency regulation capability through impedance response, eliminating the need for large-disturbance events and PMU-based parameter identification, and establishing a non-intrusive equivalent frequency response model to assess the power system's inertia level and frequency regulation performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large-disturbance event-dependent offline evaluation and PMU-based online identification are used to evaluate inertia and frequency regulation capability, then evaluation can be performed, but accuracy is low, data demand is large, and robustness is poor
Solution Approach 1:
The patent extracts the essential frequency response characteristics from impedance response data, separating the key inertial information from the complex power system measurements. By focusing on the impedance response at the PCC and extracting frequency response functions, the method obtains accurate inertia evaluation with reduced data requirements compared to comprehensive PMU-based approaches.
Solution Approach 2:
The patent introduces impedance response as an intermediary measurement that bridges the gap between direct frequency measurements and inertia evaluation. Instead of requiring extensive PMU data, the method uses impedance response characteristics as a mediator to infer frequency response and evaluate inertia, thereby reducing data demand while maintaining accuracy.
2Ease of operation
If PMU-based online identification is used for inertia evaluation, then online assessment is possible, but the method is not suitable for normal state and small disturbance analysis
Solution Approach 1:
The patent creates a universal evaluation method based on impedance response that functions across multiple operating conditions. The same impedance-based frequency response function can evaluate inertia during normal operation, small disturbances, and large disturbances, eliminating the need for different evaluation methods for different operating states and enhancing adaptability.
Solution Approach 2:
The patent changes the measurement parameter from direct frequency measurements (PMU) to impedance response characteristics. This parameter transformation enables the evaluation method to work effectively under normal operating conditions and small disturbances where frequency variations are minimal, making the system adaptable to a broader range of operating states.
3Measurement precision
If conventional evaluation methods are used, then inertia can be assessed, but the contribution of virtual inertia resources from generation-grid-load-storage is not effectively reflected
Solution Approach 1:
The patent segments the power system into generation, grid, load, and storage components and evaluates the frequency response contribution of each segment through impedance characterization. By analyzing the impedance response at different nodes and injecting disturbances at specific points, the method isolates and quantifies the virtual inertia contribution from each component type, preventing information loss about distributed inertia resources.
Solution Approach 2:
The patent implements a feedback mechanism where impedance response measurements are continuously used to update the frequency response function and evaluate inertia contributions. This feedback loop captures the dynamic behavior of virtual inertia resources from generation-grid-load-storage, ensuring their contributions are accurately reflected in the overall inertia assessment rather than being lost in aggregate measurements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise regulation of inertia and frequency regulation capability, enhancing the power system's stability and resilience against large-capacity active-power impacts, such as HVDC blockages and new energy disconnections, ensuring safe and stable operation of low-inertia power systems.
Implementation Method 1
acquiring a first frequency response function FR(s) of the power system at a point of common coupling (PCC) where the active power disturbance is injected according to Fourier transform
Data Source
AI summary
A method and a system for evaluating inertia of a power system and a storage medium. The method includes: injecting a cosine active power disturbance into the power system by small-disturbance injection, and obtaining frequency response at a node where the disturbance is injected, where the active power disturbance can be an energy storage, wind power, or photovoltaic power; acquiring an evaluation framework of inertia and frequency regulation capability of the power system according to relative characteristics of a frequency response function; and constructing a mathematical relationship between the impedance and frequency response characteristics according to a relationship among active power disturbance, frequency fluctuation and impedance.