Parallel Power Converter Current Balancing via Sensor Segmentation
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Solution Overview
Problem
Conventional power converting apparatuses require detecting the difference between positive-terminal and negative-terminal current components at the same point in time to correct output imbalances among parallel-operated forward power converters, limiting the arrangement of current sensors and imposing constraints on system design.
Innovation Solution
A power converting apparatus that detects individual output DC currents of three-phase converters and corrects AC-side voltage commands to reduce differences between these currents, allowing for balanced operation without needing to detect both current components simultaneously, thereby improving sensor arrangement flexibility and design freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the difference between positive-terminal current component and negative-terminal current component is detected at the same point in time, then the circulating current can be decreased, but the arrangement of current sensors is limited
Solution Approach 1:
The patent divides the current detection function into separate detection of positive-terminal current and negative-terminal current at different locations, rather than requiring simultaneous detection of both at the same point. This segmentation allows sensors to be arranged flexibly while still enabling calculation of current differences through computational processing of the separated measurements.
Solution Approach 2:
The patent introduces computational processing as an intermediary that calculates the difference between positive and negative terminal currents based on separately detected current values. This computational mediator eliminates the need for direct simultaneous measurement at the same point, thereby freeing sensor arrangement constraints while maintaining the ability to detect circulating currents.
2Adaptability or versatility
If individual output DC currents are detected and AC-side voltage commands are corrected, then output imbalance can be corrected without simultaneous detection of both current components, but the detection and control complexity increases
Solution Approach 1:
The patent implements feedback control by detecting individual output DC currents, comparing them to determine imbalances, and then correcting AC-side voltage commands based on these comparisons. This closed-loop feedback mechanism automatically adjusts the system to maintain balanced operation, managing the control complexity through systematic feedback processing rather than complex simultaneous measurements.
Solution Approach 2:
The patent performs preliminary detection of individual output DC currents and calculates imbalances before making corrections to the AC-side voltage commands. This preliminary action allows the system to prepare correction signals in advance based on detected imbalances, simplifying the overall control process by separating detection and correction phases rather than requiring complex simultaneous operations.
Data Source
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AI summary
In a power converting apparatus in which two three-phase converters (1, 2) are operated in parallel to one another, the three-phase converters (1, 2) are controlled by using d-axis and q-axis voltage commands. DC current sensors (26, 27) detect individual output DC currents (26a, 27a) of the three-phase converters (1, 2), and a d-axis voltage command (vdr) for each of the three-phase converters (1, 2) is corrected in a manner that reduces a difference between the output DC currents (26a, 27a). In this way, an output imbalance between the two three-phase converters (1, 2) is corrected while decreasing limitations on arrangement of the DC current sensors (26, 27).