Leakage Current Compensator Circuit With Active PE Injection
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Solution Overview
Problem
Existing systems fail to effectively compensate for leakage currents in grid-connected devices, particularly in non-isolated electronic power converters, leading to potential safety hazards and non-compliance with electrical safety standards.
Innovation Solution
A leakage current compensator (LCC) circuit with open and closed loop measurement coils and a current injector, which actively cancels leakage currents by injecting compensation currents through a virtual ground and PE conductor, providing a full return path for leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional residual current monitoring devices are used, then leakage current detection is provided, but active compensation of leakage current is not achieved
Solution Approach 1:
The patent converts the harmful leakage current into a beneficial signal by measuring it with residual current coils and using it to generate compensation current. The measured leakage current is transformed through operational amplifiers and current mirrors to produce an equal and opposite compensation current that cancels the original leakage, turning the harmful effect into a useful control signal.
Solution Approach 2:
The patent introduces intermediary components including operational amplifiers (OA1, OA2, OA3), current mirrors, and residual current coils that act as mediators between the leakage current source and the compensation mechanism. These intermediaries transform and transmit the leakage signal through multiple stages to generate the compensation current while isolating different parts of the circuit.
2Difficulty of detecting and measuring
If simple leakage current measurement is used, then detection is provided, but active cancellation of leakage current is not achieved
Solution Approach 1:
The patent implements feedback mechanisms where the measured leakage current is continuously fed back through operational amplifiers and current mirrors to generate real-time compensation current. The residual current coils continuously monitor the leakage, and the compensation current is adjusted dynamically to maintain cancellation, ensuring reliable compensation throughout operation.
3Device complexity
If no compensation circuit is used, then device complexity is low, but electrical safety standards compliance is compromised
Solution Approach 1:
The patent segments the compensation function into distinct modular components: residual current coils for measurement, operational amplifiers for signal processing, current mirrors for current transformation, and a PE conductor connection for compensation current injection. This segmentation allows each component to perform its specific function while maintaining overall system manageability and compliance.
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 LCC circuit effectively reduces leakage currents to below predetermined thresholds, enhancing safety and compliance with electrical standards by actively canceling leakage currents in various electrical systems.
Implementation Method 1
Both residual current coils may be provided as current transformers, summing all AC input lines and neutral line currents and transforming it by the winding ratio to the measurement winding
Implementation Method 2
The current injector injects what is measured by the open loop measurement coil and an additional or modified current as determined by a closed loop gain from the closed loop measurement coil
Data Source
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AI summary
The invention refers to a leakage current compensator circuit (10; 50; 60) comprising: - a plurality of current carrying wires electrically coupled to a power supply and an electrical load (12), each of the power supply and the electrical load (12) including a protective earth terminal; - a protective earth conductor (20) electrically coupled to the protective earth terminal of the power supply and the protective earth terminal of the electrical load (12); - a measurement circuit for measuring a leakage current in the plurality of current carrying wires; and - a current injector (22) electrically coupled to the plurality of current carrying wires, wherein the current injector (22) is configured to actively cancel the leakage current in the plurality of current carrying wires by injecting a compensation current into the protective earth conductor (20) based on the output of the measurement circuit.