Voltage Stability Monitoring via Segmented Thevenin Tracking
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Solution Overview
Problem
Existing methods for monitoring voltage stability in transmission corridors often lead to false alarms due to inaccurate tracking of the Thevenin equivalent of the power generating part, which can result in premature detection of voltage instability.
Innovation Solution
A method that monitors the equivalent load impedance and separately updates the Thevenin equivalent voltage and impedance at the power generating part interface, using phasor measurements to compute an index indicating voltage stability, thereby preventing false alarms by accurately tracking the Thevenin equivalent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If known tracking techniques are used to estimate Thevenin equivalent impedance, then real-time monitoring capability is achieved, but measurement precision deteriorates leading to false alarms
Solution Approach 1:
The patent segments the tracking process into two distinct parts: (1) tracking the Thevenin equivalent impedance using recursive least squares, and (2) updating the Thevenin equivalent voltage separately based on voltage phasor measurements. This segmentation allows each parameter to be optimized independently, resolving the contradiction between real-time monitoring speed and measurement precision.
Solution Approach 2:
The patent changes the approach from jointly estimating voltage and impedance to separately updating them. The Thevenin equivalent impedance is tracked using recursive least squares while the voltage is updated separately using voltage phasor measurements and equivalent load impedance variations. This parameter change enables both real-time monitoring and improved accuracy.
2Ease of manufacture
If Thevenin equivalent voltage and impedance are updated together, then computational simplicity is maintained, but measurement precision deteriorates
Solution Approach 1:
The patent divides the update process into separate operations: Thevenin equivalent impedance is updated using recursive least squares based on current and voltage measurements, while Thevenin equivalent voltage is updated separately using voltage phasor measurements and equivalent load impedance variations. This segmentation improves measurement precision without significantly increasing computational complexity.
Solution Approach 2:
The patent performs preliminary tracking of the Thevenin equivalent impedance using recursive least squares before updating the voltage. This preliminary action establishes an accurate impedance baseline that improves the overall precision of voltage stability detection while maintaining computational efficiency through staged processing.
Data Source
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AI summary
A voltage stability monitoring apparatus (8) monitors the voltage stability of a transmission corridor (6) through which power flows between different parts of a power system (2). The apparatus (8) monitors an equivalent load impedance at an interface between the transmission corridor (6) and a part of the power system (2) designated as generating the power. This equivalent load impedance at the interface comprises a ratio of a voltage phasor at the interface to a current phasor at the interface. The apparatus (8) tracks a Thevenin equivalent voltage and impedance of the designated part by separately updating that voltage and impedance. Notably, the apparatus (8) updates the imaginary part of the Thevenin equivalent voltage to reflect the magnitude of any changes in the voltage phasor that are associated with large variations in the magnitude of the equivalent load impedance at the interface. The apparatus (8) computes an index indicating the voltage stability as a function of this tracked Thevenin equivalent voltage and impedance.