Power Converter Current Sensing for Partial Discharge Control
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Solution Overview
Problem
Existing electric drive systems face challenges in monitoring partial discharges in electrical machines, which can lead to insulation issues and reduced performance, while maintaining reliability and efficiency without significantly increasing complexity or cost.
Innovation Solution
A circuit arrangement using a combination of Rogowski coils and other current sensors to detect partial discharges and monitor power output, with a computing unit to adjust power converter control accordingly, ensuring no partial discharges occur.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If WBG power semiconductors with high switching speeds are used to reduce power losses and improve efficiency, then the power converter's efficiency and performance are improved, but the voltage stress on the insulation increases leading to higher probability of partial discharges
Solution Approach 1:
The system performs preliminary detection of partial discharges using current sensors before they can cause significant insulation damage. By continuously monitoring the supply lines for characteristic high-frequency current pulses, the system can take preventive action (reducing switching frequency or shutting down) before the partial discharges lead to insulation failure, thus allowing the use of WBG semiconductors without compromising reliability.
Solution Approach 2:
The control system uses feedback from current sensor measurements to dynamically adjust the power converter's operation. When partial discharges are detected through characteristic current pulse patterns, the control system reduces the switching frequency or shuts down the converter, creating a closed-loop system that balances efficiency optimization with insulation protection.
2Reliability
If insulation type I is used to ensure no partial discharges throughout service life, then reliability is improved, but insulation thickness must be increased which limits performance and increases complexity
Solution Approach 1:
The monitoring system enables the insulation to effectively protect itself by detecting partial discharges and triggering control actions that prevent further damage. The current sensors and control unit create a self-protecting system that allows thinner insulation (type II) to achieve the same reliability as thicker insulation (type I) by actively managing partial discharge events rather than passively relying on insulation thickness.
Solution Approach 2:
The system dynamically changes operational parameters (switching frequency, power output) based on detected partial discharge conditions. When partial discharges are detected, the control system adjusts these parameters to reduce voltage stress on the insulation, effectively adapting the operating conditions to protect the insulation without requiring increased thickness.
3Measurement precision
If separate systems are used for power monitoring and partial discharge detection, then monitoring accuracy is improved, but system complexity and costs increase significantly
Solution Approach 1:
The current sensors serve dual functions: they monitor the power output and torque of the electrical machine while simultaneously detecting partial discharges through analysis of high-frequency current pulse components. The control unit processes both functions using the same sensor inputs, eliminating the need for separate monitoring systems while maintaining accuracy for both power measurement and partial discharge detection.
Solution Approach 2:
The system merges the power monitoring function and partial discharge detection function into a single integrated monitoring approach. By combining the analysis of current signals for both torque calculation and partial discharge detection, the system achieves comprehensive monitoring without duplicating sensors or processing hardware, thus reducing complexity and costs while maintaining measurement precision.
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
Enhances the reliability and efficiency of electric drive systems by effectively detecting and preventing partial discharges, reducing the risk of insulation failure and maintaining desired torque and speed.
Implementation Method 1
Partial discharges on the winding insulation of an electric drive motor lead to high-frequency current pulses in its supply line(s), which can be measured using a current sensor, for example.
Data Source
AI summary
The present disclosure provides a method for controlling and monitoring an electrical machine powered by a power converter. The method comprises detecting a current at at least one output of the power converter by means of at least one first current sensor having a Rogowski coil, determining a first monitoring variable for monitoring the electrical machine for partial discharges based on a first evaluation of the detected current, determining a second monitoring variable for monitoring a load current of the power converter based on a second evaluation of the detected current, and controlling the power converter using the determined first monitoring variable and the determined second monitoring variable. A computing unit and a circuit arrangement for implementing the method are also provided.