Parallel Active Filters with Line Side Sensing and Current Difference Feedback
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Solution Overview
Problem
Current parallel configurations of electronic active filters in industrial systems face challenges with circulating currents when using line side sensing, leading to reduced performance and inability to effectively parallel filters without open-loop control limitations.
Innovation Solution
Implementing a parallel filter circuit with line side sensing electronic active filters that utilize current difference feedback to adjust and synchronize harmonic current outputs, minimizing circulating currents and enabling effective parallel operation through closed-loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple electronic active filters are connected in parallel with line side sensing to increase filtering capacity, then the ability to compensate harmonics is improved, but circulating currents are generated between filters reducing system performance
Solution Approach 1:
The patent implements a feedback mechanism where each filter's current output is sensed and fed back to all filters in the parallel configuration. This feedback allows each filter to adjust its current contribution based on the actual performance of other filters, enabling automatic balancing of current sharing and elimination of circulating currents while maintaining enhanced harmonic compensation capability
Solution Approach 2:
The control system dynamically adjusts the operating parameters of each filter based on real-time conditions. By continuously monitoring and adapting the current reference signals for each filter according to their actual performance and system conditions, the system optimizes current distribution and prevents circulating current generation
2Device complexity
If electronic active filters operate in open-loop control mode to simplify control structure, then device complexity is reduced, but performance and accuracy of harmonic compensation deteriorates
Solution Approach 1:
The patent employs feedback control where the actual current output of each filter is continuously measured and compared with the reference current. The error signal is used to adjust the filter operation, ensuring accurate tracking of the desired current waveform and maintaining high harmonic compensation accuracy while providing a complete control solution
3Device complexity
If electronic active filters are paralleled without current difference feedback to reduce control complexity, then device complexity is reduced, but circulating currents increase reducing productivity
Solution Approach 1:
The patent implements current difference feedback that directly measures and utilizes the current differences between parallel filters. This feedback mechanism provides each filter with information about its relative performance, enabling automatic current sharing optimization and elimination of circulating currents, thereby maintaining high system efficiency without excessive control complexity
Data Source
AI summary
A parallel filter arrangement with at least two filters supplying current in line side sensing configuration and a number of sensors for measuring current. The sensors are used to determine the amount of current being supplied by the filters and the amount of current being supplied by a source. The filters adjust their supplied current in order to reduce or eliminate the amount of reactive or harmonic current being supplied by a source.