Insulation Detecting Circuit Ground Impedance Detection
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Solution Overview
Problem
In solar power generating systems, power converting devices face grounding failures that can lead to leakage currents, causing device failure or accidents, necessitating a reliable ground impedance detection mechanism to ensure safe operation.
Innovation Solution
A power converting device with an insulation detecting circuit that uses a processing unit, resistors, and a switching unit to calculate ground impedance by analyzing the cross voltage across a detecting resistor, even at low input voltage levels, and can output a warning signal or stop operation if impedance falls below a safety limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ground impedance detecting function is added to ensure safe operation, then device safety and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent combines the ground impedance detection function with the existing DC-DC converting circuit by sharing the capacitor unit and switching unit. The detection circuit uses the same capacitor that is already part of the power conversion circuitry, merging two functions (power conversion and safety detection) into a single integrated system, thereby reducing overall complexity while maintaining safety.
Solution Approach 2:
The capacitor unit and switching unit serve dual purposes: they are essential components for the DC-DC power conversion operation and simultaneously enable the ground impedance detection function. This multi-functionality eliminates the need for separate dedicated detection components, reducing device complexity while ensuring reliable safety monitoring.
2Measurement precision
If multiple insulation detecting circuits are used to ensure accurate detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent performs ground impedance detection at the DC input side before power conversion, where the voltage level is already suitable for accurate measurement. By conducting the detection preliminary at this stage using the available capacitor and switching unit, the system achieves accurate measurement without requiring multiple detection circuits or complex signal conditioning stages.
3Productivity
If detection is performed at low input voltage levels, then operational continuity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent implements a control mechanism that monitors the DC input voltage level and selectively activates the ground impedance detection function. When the input voltage is below a predetermined threshold, the detection is enabled to ensure safety; when voltage is sufficient, normal operation continues without detection interference. This feedback-based selective operation maintains both operational continuity and measurement precision by optimizing detection timing based on actual voltage conditions.
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 solution accurately detects ground impedance, reducing the risk of device damage or accidents by ensuring continuous operation and reducing the need for multiple insulation detecting circuits, thereby lowering costs and circuit complexity.
Implementation Method 1
an insulation detecting circuit electrically coupled between the output terminals of the dc-dc converting circuits and the input terminal of the dc-ac converting circuit, and configured to detect a ground impedance value according to a dc bus voltage
Data Source
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Figure 3A~3B
AI summary
A power converting (100) device includes a DC-DC converting circuit (120), a DC-AC converting circuit (180), and an insulation detecting circuit (160). The DC-DC converting circuit is configured to convert a DC input voltage (Vin1) to a DC bus voltage (Vbus). The DC-AC converting circuit is electrically coupled to the DC-DC converting circuit and configured to convert the DC bus voltage to an AC voltage (Vac). The insulation detecting circuit is electrically coupled between the DC-DC converting circuit and the DC-AC converting circuit. The insulation detecting circuit is configured to detect a ground impedance value of the power converting device according to the DC bus voltage.