Online Partial Discharge Detection in Converter-Fed Electric Drives
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Solution Overview
Problem
Current methods for measuring partial discharges in electrical drive systems, particularly those with converter-fed rotating machines, require offline operations due to the need for a smooth sinusoidal voltage signal, leading to costly downtime and production losses.
Innovation Solution
A method that continuously analyzes the sinusoidal converter signal generated by the converter, detects deviations from a reference signal to identify partial discharges, and uses a control unit and partial discharge measuring system with signal analysis and digital processing to enable online measurements during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offline partial discharge measurements are performed using a sinusoidal reference signal, then measurement precision is improved, but productivity deteriorates due to system downtime and production loss
Solution Approach 1:
The patent applies dynamics by making the measurement system adaptable to different operating conditions. The control unit dynamically adjusts the measurement process based on converter switching states, enabling measurements during operation rather than requiring static offline conditions. This transforms the measurement system from a stationary offline tool to a dynamic online monitoring system.
Solution Approach 2:
The patent implements preliminary action by continuously monitoring converter signals and identifying suitable measurement windows before actual partial discharge detection. The control unit pre-analyzes converter switching patterns to determine optimal moments when switching interference is minimal, preparing the measurement in advance to ensure accuracy during operation.
2Productivity
If online partial discharge measurement is attempted during converter operation, then productivity is improved by avoiding downtime, but measurement precision deteriorates due to converter switching interference
Solution Approach 1:
The patent extracts the harmful converter switching interference from the measurement process by identifying and excluding time periods with switching activity. The control unit separates the measurement into valid windows (without switching interference) and invalid windows (with switching interference), taking out only the clean portions for analysis. This isolation technique enables accurate measurements during converter operation.
Solution Approach 2:
The control unit acts as an intermediary between the converter and the measurement system. It continuously monitors converter switching signals and uses this information to gate the measurement process, enabling measurements only when conditions are favorable. This intermediary function协调s the conflicting requirements of continuous operation and accurate measurement.
3Speed
If converter switching frequency is increased to improve response speed, then speed is improved, but device complexity increases due to more frequent switching interference
Solution Approach 1:
The patent implements feedback by using the control unit to continuously monitor converter switching signals and use this information to adjust the measurement process in real-time. The control unit receives feedback about switching events and dynamically modifies measurement windows accordingly. This feedback mechanism enables the system to handle high switching frequencies without increasing complexity, as the same control unit manages both monitoring and measurement coordination.
Data Source
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AI summary
The invention relates to a method for measuring a partial discharge (Te) in an electric drive system (2) which comprises an electric rotating machine (4) and a converter (6). In order to be able to carry out the method during the operation of the electric drive system (2), a signal shape of a converter signal (R, S, T) generated by the converter (6) is analyzed continuously, with a measurement signal (M) being detected while the converter signal (R, S, T) has a sinusoidal signal shape, the measurement signal (M) being compared with a reference signal (Rs), and a partial discharge (Te) being detected while a deviation of the measurement signal (M) from the reference signal (Rs) exceeds a threshold value (Sw).