Parallel DC/DC Converter Control for Uniform Bus Output Sharing
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Solution Overview
Problem
In large-capacity energy storage systems using lithium ion batteries, maintaining uniform outputs among multiple DC/DC converters connected in parallel is challenging due to voltage detection deviations and wiring impedance differences, especially without relying on fast communication.
Innovation Solution
A DC/DC conversion system where each DC power supply is connected to a common DC bus via a DC/DC converter and a control unit that corrects voltage detection values by accounting for individual deviations among multiple converters, and controls the converters using droop characteristics-based voltage command values to ensure equal outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple DC/DC converters are connected in parallel to a common DC bus, then the system capacity and power distribution capability are improved, but output uniformity among converters deteriorates due to voltage detection deviations and wiring impedance differences
Solution Approach 1:
The patent implements a feedback mechanism where each DC/DC converter detects the DC bus voltage individually, calculates its own output based on droop characteristics, and adjusts its operation accordingly. The control unit continuously monitors the detection values and corrects deviations, creating a closed-loop control system that maintains output uniformity despite initial detection differences
Solution Approach 2:
The patent changes the voltage detection parameter by introducing correction values that compensate for individual detection deviations. By adjusting the detected voltage parameter through mathematical correction rather than physical modification, the system achieves uniform output distribution while maintaining the parallel converter configuration
2Manufacturing precision
If voltage detection values are corrected using individual deviations, then output uniformity is improved, but control complexity increases
Solution Approach 1:
Each DC/DC converter performs self-correction by detecting the DC bus voltage independently, calculating its own deviation from the average, and applying the appropriate correction value. This distributed self-service approach eliminates the need for complex centralized control while achieving output uniformity
Solution Approach 2:
The patent applies preliminary correction to the voltage detection values before they are used in control calculations. By pre-calculating and applying correction values based on individual deviations, the system simplifies the subsequent control operations and avoids the need for complex real-time adjustments
3Power
If droop characteristics are used for voltage command values, then output distribution is improved, but voltage regulation precision deteriorates
Solution Approach 1:
The patent introduces correction values as an intermediary element between the droop-based voltage command and the actual converter operation. These correction values compensate for the voltage regulation precision loss inherent in droop characteristics, allowing the system to maintain both good output distribution and acceptable voltage regulation
Data Source
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AI summary
This DC/DC conversion system is provided between a plurality of DC power supplies and a common DC bus, and includes, for each of the plurality of DC power supplies: a DC/DC converter provided between the DC power supply and the DC bus; and a control unit configured to control the DC/DC converter. The control unit corrects a voltage detection value for the DC bus by taking in an individual voltage detection deviation for the DC bus compared to an entirety of a plurality of the DC/DC converters present in parallel, and controls the corresponding DC/DC converter in accordance with a voltage command value having droop characteristics with respect to output power. The DC/DC conversion system as described above can uniform outputs while operating the plurality of DC/DC converters in parallel without the need of fast communication.