Transient State Estimation in Power Systems
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Solution Overview
Problem
Existing power system state estimation methods are ineffective during rapid transient conditions, particularly when non-sinusoidal voltage and current waveforms occur due to system disturbances, and place excessive demands on measurement instruments and communication speed.
Innovation Solution
A method using synchronized measurements over a scanning cycle with instantaneous sample data from PMUs, employing a state space model and discretized model to estimate transient states, allowing for accurate snapshotting of voltages, currents, and power flows, and adjusting power supply/demand to mitigate disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If raw measurement systems are used for state estimation, then measurement accuracy is improved, but the number of measurement instruments and processor demand increase excessively
Solution Approach 1:
The patent extracts only the essential measurement data needed for transient state estimation from the complete set of available measurements. By selectively using a subset of measurement instruments and focusing on critical state variables during transient conditions, the system achieves accurate state estimation without requiring all available measurement devices, thus reducing device complexity while maintaining measurement precision.
2Productivity
If steady state state estimation methods are used during transient conditions, then computational simplicity is maintained, but estimation accuracy deteriorates due to non-sinusoidal waveforms
Solution Approach 1:
The patent implements a dynamic state estimation approach that adapts to transient conditions by using time-varying models and algorithms capable of handling non-sinusoidal waveforms. The estimation method dynamically adjusts to the changing system state during transients, maintaining both computational efficiency and estimation accuracy by using simplified models appropriate for transient analysis rather than steady-state assumptions.
3Speed
If single time step measurement methods are used for transient state estimation, then communication speed requirements are reduced, but measurement accuracy deteriorates due to insufficient temporal resolution
Solution Approach 1:
The patent performs preliminary processing and aggregation of measurement data within each time step before transmission. By pre-processing the measurement data locally and extracting only the essential transient state information needed for estimation, the system reduces the amount of data that needs to be communicated while maintaining sufficient temporal resolution for accurate transient analysis.
4Adaptability or versatility
If existing transient state estimation methods are used, then adaptation to non-sinusoidal waveforms is improved, but communication burden and data processing requirements increase excessively
Solution Approach 1:
The patent extracts only the critical information needed for transient state estimation during non-sinusoidal conditions, rather than transmitting complete measurement datasets. By identifying and transmitting only the essential state variables and parameters required for accurate estimation, the system maintains adaptability to non-sinusoidal waveforms while significantly reducing communication burden and data processing requirements.
Data Source
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AI summary
The present invention relates to a method of controlling power flows and/or voltages in a power system. The method comprises monitoring conditions of voltage and/or current at a set of system locations for a scanning cycle of synchronised measurements. The scanning cycle comprises a series of time steps in which instantaneous sample measurements of voltage and/or current are taken. The monitoring provides data comprising the instantaneous sample measurements for a complete scanning cycle. A transient state estimation is determined based on the data for two or more sequential time steps. The transient state estimation includes an estimation of a non-sinusoidal voltage or current waveform caused by a disturbance to the power system. The method further includes forming a snapshot that includes instantaneous voltages, current flows and power flows of the power system. The method further includes making an adjustment to mitigate the effect of the disturbance. The invention also resides in a power system comprising a plurality of synchronised measurement units at locations in the power system. Each measurement unit is configured to obtain sample data over a synchronised scanning cycle comprising a series of time steps in which instantaneous sample measurements of voltages and/or currents are taken, and to transmit the instantaneous sample data for a complete scanning cycle after completion of the cycle. A transient state estimator is configured to receive and analyse the sample data to determine a transient state estimation based on the data for two or more sequential time steps. The transient state estimation includes an estimation of a non-sinusoidal voltage or current waveform caused by a disturbance to the power system. At least one power device adjusts an amount of power supplied to and/or drawn from the power system to mitigate the effect of the disturbance.