Power Converter Partial Discharge Detection With Rolling References
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Solution Overview
Problem
Reliably detecting partial discharge in power electronics-based electrical power systems, particularly at high switching frequencies, is challenging due to partial discharge signals being hidden in noise such as transient current responses or current clusters caused by voltage changes.
Innovation Solution
A detection technique that iteratively refreshes a reference signal on a rolling basis, determining a difference signal by subtracting the reference signal from the current signal at each voltage step, allowing for detection of partial discharge even at high switching frequencies by identifying magnitudes exceeding a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional detection methods are used to detect partial discharge, then the detection system is simple, but the detection reliability deteriorates at high switching frequencies due to noise masking
Solution Approach 1:
The system performs preliminary characterization of the electrical power system by applying a voltage sweep to generate reference current signals before actual partial discharge detection. This preliminary action captures the system's natural current response to voltage changes, which is then used as a baseline to distinguish partial discharge signals from noise during operation.
Solution Approach 2:
The patent introduces an intermediary processing layer that subtracts the reference current signal from the measured current signal. This intermediary step acts as a mediator that separates the partial discharge signal from the noise by removing the expected current response, allowing reliable detection even at high switching frequencies.
2Measurement precision
If voltage changes are applied to detect partial discharge, then detection capability is improved, but transient current responses and noise increase
Solution Approach 1:
The patent converts the harmful transient current responses and noise into a useful reference signal. By deliberately applying voltage sweeps and capturing the resulting current responses, the system creates a reference that contains the same noise and transient characteristics. This reference is then subtracted from operational current signals, effectively canceling out the noise while preserving partial discharge information.
Solution Approach 2:
The system changes the voltage parameter dynamically by applying voltage sweeps at different levels during the characterization phase. This parameter change allows the system to map the relationship between voltage and current response, creating a comprehensive reference that accounts for non-linear system behavior and improves detection accuracy across different operating conditions.
3Object-affected harmful factors
If rolling reference signal refresh is implemented, then noise tolerance is improved, but computational complexity increases
Solution Approach 1:
The system implements periodic refreshing of the reference signal by continuously performing voltage sweeps and updating the reference current signal. This periodic action ensures that the reference remains current and accounts for changes in system characteristics over time, improving noise tolerance while maintaining a manageable computational burden through regular, structured updates.
Solution Approach 2:
The rolling reference refresh uses preliminary voltage sweep measurements to continuously update the reference signal before actual detection occurs. This preliminary characterization is performed in a controlled manner that separates the reference generation from the detection process, managing computational complexity by organizing operations into distinct phases.
Data Source
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AI summary
Partial discharge detection techniques are provided. In one aspect, a method (700, 800) of detecting partial discharge in an electrical power system (100) having a power electronics converter (120) is provided. A first current signal (I1) is captured in response to a first applied voltage (V1). A second current signal (12) is captured in response to a second applied voltage (V2), the second applied voltage (V2) being different than the first applied voltage (V1). The first current signal (I1) is set as a reference signal (IREF). A difference signal (ΔN) is determined based on the second current signal (12) and the reference signal (IREF). A determination is made as to whether partial discharge is present based on the difference signal (ΔN). The method (700, 800) may iterate, and for each iteration, the reference signal (IREF) is refreshed on a rolling basis as a previously captured current signal (IN-1) measured in response to a previously applied voltage (VN-1). The applied voltage is also stepped up or down for each iteration.