Ground Impedance Detection in Power Converters
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Solution Overview
Problem
Conventional power systems require dedicated and expensive detection devices to monitor ground impedance, which increases system complexity and costs. Additionally, these systems can only detect ground impedance on the alternating current side, leading to poor impedance short-circuit fault detection effects.
Innovation Solution
A power system with a converter and a short-circuit detection apparatus that can detect ground impedances on both alternating current and direct current sides without additional resistance, thereby reducing detection costs and improving fault detection range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated detection device is installed to detect ground impedance, then detection accuracy is improved, but system complexity and cost increase
Solution Approach 1:
The patent combines the ground impedance detection function with the existing converter device by integrating a detection module into the converter's control unit. This allows the converter to perform both power conversion and ground impedance detection functions, eliminating the need for a separate dedicated detection device and reducing system complexity while maintaining detection accuracy
Solution Approach 2:
The converter is designed to serve multiple functions: power conversion and ground impedance detection. The detection module within the converter uses the existing circuit components (capacitors, switching devices) to perform ground impedance measurement, making the converter a universal device that handles both operational and diagnostic tasks
2Device complexity
If the anti-potential induced degradation device is reused for ground impedance detection, then device cost is reduced, but detection capability is limited to AC side only
Solution Approach 1:
The detection module dynamically switches between detecting AC-side ground impedance and DC-side ground impedance by controlling the switching devices in different circuit configurations. This dynamic capability allows the same hardware to adapt to different detection needs, expanding the detection range from only AC side to both AC and DC sides
Solution Approach 2:
The detection method changes operational parameters (voltage application, current measurement) based on whether AC-side or DC-side ground impedance is being measured. By adjusting detection parameters and switching configurations, the system achieves versatile detection capability across different sides of the converter
3Adaptability or versatility
If external resistor is used for coordination with anti-potential induced degradation device, then detection function is achieved, but detection cost increases
Solution Approach 1:
The converter's existing circuit components (bus capacitors, switching devices, control unit) are utilized to perform ground impedance detection without requiring external resistors or additional coordination components. The detection module leverages the converter's own operational characteristics and components to achieve detection functionality, making the system self-sufficient
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
The proposed solution allows for wider impedance short-circuit fault detection, reduces detection costs by eliminating the need for additional resistance, and improves the working reliability of the power system by detecting ground impedances on both AC and DC sides.
Implementation Method 1
output a first voltage value to the equivalent neutral point, obtain a first current value of the short-circuit detection apparatus in a case in which the first voltage value is output, output a second voltage value to the equivalent neutral point, and obtain a second current value of the short-circuit detection apparatus in a case in which the second voltage value is output
Data Source
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AI summary
This application provides a power system and a method for detecting a ground impedance. The power system includes a converter and a short-circuit detection apparatus The converter includes a positive bus capacitor and a negative bus capacitor that are connected in series, and a series connection point between the two bus capacitors is a neutral point. The short-circuit detection apparatus is connected to an equivalent neutral point. A ground potential difference of the equivalent neutral point is positively correlated with a ground potential difference of the neutral point. The equivalent neutral point includes a connection end of three phases of output ends of the converter. The short-circuit detection apparatus outputs a first voltage value and a second voltage value to the equivalent neutral point, and obtains a first current value and a second current value of the short-circuit detection apparatus when the first voltage value and the second voltage value are output. The short-circuit detection apparatus obtains a ground impedance of the power system based on the first voltage value, the second voltage value, the first current value, and the second current value, and reports or sends ground impedance abnormality fault information when the ground impedance is less than a specified threshold. According to this application, ground impedances of an alternating current side and a direct current side of the power system can be detected, and a ground impedance detection range is wide.