Petersen Coil Parameter Detection from Zero-Voltage Transients
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Solution Overview
Problem
Existing methods for determining network parameters for Petersen coils in power networks are inefficient, particularly when natural asymmetry occurs, as they require waiting for settling times and are unable to reliably determine parameters in healthy network conditions.
Innovation Solution
A method involving continuous sampling of zero voltage signals during transient decay processes, transforming them into the complex image area, and calculating vectorial differences to determine angular velocity deviations and damping, allowing for reliable parameter determination within a network frequency period, even with natural asymmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency analysis is carried out for multiple frequency components to determine natural frequency, then measurement precision is improved, but productivity deteriorates due to time-consuming settling time requirements
Solution Approach 1:
The patent applies preliminary action by intentionally generating a transient decay process through a ground fault or modulation current injection before parameter determination. This pre-prepared transient signal provides sufficient frequency information immediately, eliminating the need to wait for natural settling time after a ground fault. The transient decay process is created in advance to contain the necessary spectral information for rapid parameter extraction.
Solution Approach 2:
The patent uses partial action by analyzing only the most relevant frequency components during the transient decay process rather than performing exhaustive analysis across all possible frequencies. The method focuses on extracting parameters from the dominant frequency components present in the transient signal, achieving sufficient precision without the computational overhead of complete frequency spectrum analysis.
2Measurement precision
If parameter determination is performed after ground fault extinguishing, then measurement precision is improved by using decay process data, but adaptability deteriorates when natural asymmetry prevents zero crossing determination
Solution Approach 1:
The patent introduces an intermediary approach by using modulation current injection as an alternative excitation source when natural ground faults are unavailable or unsuitable. This intermediary method generates a controlled transient decay process that provides reliable measurement data regardless of natural asymmetry conditions. The modulation current acts as a mediator to create the necessary transient signal for parameter determination without relying on natural system asymmetries.
Solution Approach 2:
The patent applies parameter changes by deliberately modifying system parameters through modulation current injection to create a transient decay process. By changing the excitation parameter from natural ground fault to controlled modulation current, the method ensures consistent and reliable parameter determination. The modulation frequency and amplitude are adjusted to optimize the transient signal characteristics for accurate parameter extraction.
3Measurement precision
If comprehensive frequency analysis is performed to evaluate admittance and conductivity at each frequency, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential parameters needed for Petersen coil control from the transient decay signal, rather than performing comprehensive analysis of all frequency components. The method specifically extracts natural frequency, admittance, and conductivity parameters from the dominant frequency components present in the transient signal, discarding redundant information. This selective extraction reduces computational complexity while maintaining sufficient measurement precision for control applications.
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
Enables rapid and accurate determination of network parameters for Petersen coil control, reducing resource expenditure and compensating for frequency deviations, thus ensuring effective capacitive ground fault current compensation.
Implementation Method 1
A Petersen coil which compensates for the capacitive ground fault current by forming a parallel resonant circuit that minimizes the current across the ground fault point
Implementation Method 2
the continuous zero voltage signal is sampled during a transient decay process over a period of the nominal frequency and is transformed into the complex image area
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
A method for determining network parameters for controlling a Petersen coil (1) for earth fault compensation in a multiphase power grid with a nominal frequency is described, wherein a zero-voltage signal (17) is acquired. To design a method of the type described above in such a way that the necessary network parameters can be reliably determined within one period even in the presence of a natural asymmetry, it is proposed that the continuous zero-voltage signal (17) be sampled during a transient oscillation process over one period of the nominal frequency and transformed into the complex domain as a zero-voltage phasor U0 at each time step.whereupon, in each time step, a synchronous zero-voltage phasor U0S is formed by reducing the angular velocity of the zero-voltage phasor U0 by a reference angular velocity ωN, and the vector difference (18) between two synchronous zero-voltage phasors U0S with a predetermined time interval is determined in each time step, after which the angular deviation (19) between the vector differences (18) of two time steps is output as the angular velocity deviation of the zero-voltage phasor U0 from the reference angular velocity ωN and/or the magnitude deviation of the vector differences (18) of two time steps is output as the damping (21) of the zero-voltage phasor U0.