Out-of-Step Prediction Using Rotor Angle Differential
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Solution Overview
Problem
Existing power system stability models struggle to accurately predict out-of-step conditions due to inaccuracies in dynamic mathematical models, especially during cascading failures, leading to poor detection and prediction performance.
Innovation Solution
A method that calculates the differential value between a rotor angle of an individual generator and the equivalent rotor angle of the center of inertia, using a central control unit to process data and apply the Prony method for curve fitting and stability assessment, allowing for real-time prediction of out-of-step conditions without relying on inaccurate dynamic models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If dynamic mathematical models are used to detect and predict out-of-step conditions, then the detection capability is provided, but the accuracy deteriorates due to model inaccuracies especially during cascading failures
Solution Approach 1:
The patent extracts the essential information needed for out-of-step detection (rotor angle differences and their rates of change) without relying on the complete dynamic mathematical model. By taking out only the critical measurements and relationships, the system achieves accurate detection without the inaccuracies inherent in full dynamic models during cascading failures
Solution Approach 2:
Instead of using the complex dynamic mathematical model directly, the patent creates a simplified representation that copies only the essential behavior needed for detection - the relative rotor angle dynamics. This simplified copy avoids the modeling errors present in the full dynamic model while preserving the critical out-of-step detection capability
2Extent of automation
If local control units calculate equivalent rotor angle independently, then detection autonomy is improved, but processing overhead and communication burden increase significantly
Solution Approach 1:
The patent merges the calculation of the equivalent rotor angle at a central control unit rather than having each local control unit calculate it independently. This consolidation reduces redundant computations and minimizes communication overhead, as the central unit computes the aggregate system angle once and makes it available to all local units
Solution Approach 2:
The central control unit performs multiple functions: it calculates the equivalent rotor angle, monitors system-wide stability, and provides data to all local control units. This multi-functional approach reduces overall system complexity compared to having each local unit perform the full calculation independently
Data Source
AI summary
In the field of power system stability there is provided a method of predicting the presence of an out-of-step condition in a power system that includes a plurality of generators, the method including the steps of:(a) obtaining a differential value ({tilde over (δ)}COIk) between a rotor angle (δk) of an individual one of the plurality of generators and an equivalent rotor angle (δCOIk) of the centre of inertia of the remainder of the plurality of generators;(b) processing the differential value ({tilde over (δ)}COIk) to determine whether the differential value ({tilde over (δ)}COIk) is predicted to reach a predefined reference threshold (δthreshold); and(c) predicting the presence of the out-of-step condition in the power system if the differential value ({tilde over (δ)}COIk) is predicted to reach the predefined reference threshold (δthreshold).