Parallel DC/DC Converter Control With Droop-Based Output Balancing
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Solution Overview
Problem
In large-capacity energy storage systems, maintaining uniform output among multiple DC/DC converters connected in parallel is challenging due to voltage detection deviations and wiring impedance differences, requiring fast and reliable communication to control DC bus voltage, which is difficult to achieve with existing technologies.
Innovation Solution
A DC/DC conversion system with a control unit that corrects voltage detection values and controls DC/DC converters using droop characteristics, allowing them to operate uniformly without relying on fast communication by adjusting voltage command values based on individual voltage detection deviations and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple DC/DC converters are connected in parallel to maintain uniform output, then the system capacity and reliability are improved, but voltage detection deviations and wiring impedance differences cause output imbalance requiring fast communication for control
Solution Approach 1:
Each DC/DC converter independently detects its own output voltage and current, calculates its output power, and autonomously adjusts its output according to droop characteristics without requiring fast communication with other converters. The converter serves itself by using locally available measurements to maintain uniform output distribution.
Solution Approach 2:
The system changes the control parameter from fixed voltage control to droop characteristics control, where the voltage command value varies with output power. This allows automatic load sharing among parallel converters based on their individual capabilities, eliminating the need for complex communication protocols to maintain output uniformity.
2Measurement precision
If fast communication is implemented to control DC bus voltage, then output uniformity among converters is improved, but system cost and complexity increase
Solution Approach 1:
The control unit continuously monitors the output voltage and current of each DC/DC converter, calculates the output power, and feeds this information back to adjust the voltage command value according to droop characteristics. This closed-loop feedback mechanism ensures accurate voltage detection and automatic load sharing without requiring fast communication between converters.
3Ease of operation
If voltage detection values are not corrected for individual deviations, then system operation is simpler, but output uniformity among converters deteriorates
Solution Approach 1:
The system applies individualized voltage detection correction to each DC/DC converter based on its specific wiring impedance and detection characteristics. Each converter uses its own correction coefficient to compensate for local deviations, maintaining output uniformity without requiring complex centralized control or communication.
Data Source
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.