State Estimation Accuracy Verification via Phasor Measurements
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Solution Overview
Problem
Current state estimation methods in power systems face inaccuracies due to measurement errors, lack of synchronization, and changing network parameters and topology, leading to potential biases and unsatisfactory convergence, especially in fringe areas with weak redundancy, without a reliable indicator for verifying the accuracy of the estimation procedure.
Innovation Solution
A method that uses phasor measurements from multiple PMUs at distinct substations to verify the accuracy of state estimation by comparing dependent system quantities like phase angle differences, allowing for a discrepancy threshold evaluation to determine the reliability of state estimation results and potentially reduce operational security margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If state estimation is performed using conventional measurement methods, then the procedure can be implemented with existing infrastructure, but the accuracy of estimation results deteriorates due to measurement errors and lack of synchronization
Solution Approach 1:
The patent introduces an accuracy verification mechanism that acts as an intermediary between the state estimation procedure and the operational decisions. This verification step compares estimated states with expected physical relationships (such as phase angle differences between synchronized measurements) to detect potential biases without requiring complete replacement of the measurement infrastructure.
Solution Approach 2:
The patent changes the approach from directly trusting estimation results to verifying them through additional parameter checks. By introducing verification parameters (such as phase angle differences from synchronized measurements) and comparing them against expected ranges, the system can detect accuracy degradation without fundamental changes to the state estimation algorithm itself.
2Measurement precision
If PMUs are deployed at all locations to ensure accurate measurements, then measurement accuracy improves, but system complexity and cost increase significantly
Solution Approach 1:
The patent applies partial action by deploying PMUs only at selected critical locations rather than at all measurement points. The accuracy verification procedure is designed to work with this partial synchronization, using the available synchronized measurements to detect biases in the state estimation results without requiring complete system-wide PMU deployment.
Solution Approach 2:
The patent makes the synchronized PMU measurements serve multiple functions: they provide accurate reference data for state estimation, enable accuracy verification through phase angle comparisons, and detect potential biases in the estimation procedure. This multi-functionality maximizes the value of the limited PMU deployment.
3Reliability
If security margins are maintained to ensure operational safety, then system reliability is preserved, but power transmission capacity is reduced
Solution Approach 1:
The patent introduces a feedback mechanism where the accuracy verification results directly influence the decision-making process regarding security margins. When verification confirms high accuracy, the system can reduce security margins and increase transmission capacity; when verification detects potential biases, the system maintains conservative margins to ensure safety.
Solution Approach 2:
The patent makes the security margin setting dynamic rather than static. Security margins are adjusted based on the real-time accuracy verification results, allowing the system to optimize transmission capacity while maintaining safety when conditions permit, and to become more conservative when accuracy concerns arise.
4Measurement precision
If redundant measurements are increased to improve state estimation accuracy, then estimation precision improves, but measurement system complexity and cost increase
Solution Approach 1:
The patent changes the approach from increasing the quantity of measurements to changing the quality and utilization of existing measurements. The accuracy verification procedure extracts additional value from the existing measurement set by checking consistency with expected physical relationships, rather than simply adding more measurement devices.
Data Source
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AI summary
The present invention is concerned with the reduction of an operational security margin of a power system (1) without jeopardizing the safety of the power system or incurring heavy investments. According to the invention, a check for basic accuracy or correctness of a conventional State Estimation (SE) procedure allows to increase a level of confidence in the results of the procedure. To this end, an accuracy of the estimated states is verified by comparing the latter with the results (y, y´) of independent phasor measurements performed at selected locations (B, D) of the power system. Unless a discrepancy is reported by this comparison, the results of the SE can be assumed to be sufficiently accurate, and any conservative or additional security margin intended to compensate for SE uncertainty can be relaxed. Hence, established trustworthiness in the estimated states allows increasing the transmitted power where the estimated states do indicate such a possibility, i.e. in particular in fringe areas and/or transmission corridors between countries, and especially under stressed network conditions.