DC Power Converter Droop Control for Accurate Parallel Current Sharing
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Solution Overview
Problem
Existing DC power supply systems face challenges in achieving high reliability and precise control of output current, particularly in parallel operation scenarios where information exchange between converters is limited.
Innovation Solution
A power conversion device that includes an output current value acquisition unit, an output voltage value acquisition unit, and a controller. The controller generates an output current correction value based on an output current target value and the actual output current, and uses this correction value to droop the output voltage target value, allowing for reliable control of output current without information exchange between converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If droop control is used to enable reliable parallel operation without information exchange, then system reliability is improved, but output current control capability deteriorates
Solution Approach 1:
The patent introduces a feedback mechanism where each converter monitors its own output current and voltage, and adjusts its droop characteristics based on this feedback. The controller generates correction values based on the difference between actual and target output current, dynamically adjusting the droop slope to achieve both reliability and current control capability.
Solution Approach 2:
Each power converter independently performs droop control based on its own output current and voltage measurements without requiring information exchange with other converters. The system achieves coordinated current sharing through self-service droop characteristics, where each unit autonomously adjusts its operating point based on local feedback.
2Ease of operation
If master-slave scheme is used to achieve arbitrary voltage and current control, then output current control capability is improved, but system reliability deteriorates
Solution Approach 1:
The patent segments the control function by assigning different roles to different converters based on their operating conditions rather than designating a single master. Multiple converters can simultaneously serve as masters or slaves depending on load conditions, battery states, and control priorities, distributing the control burden and eliminating single-point failures.
Solution Approach 2:
The master-slave roles are made dynamic rather than static. Controllers can switch between master and slave modes based on real-time system conditions such as load demand, battery charge levels, and converter performance. This dynamic role assignment maintains control capability while improving reliability through redundancy.
3Reliability
If droop control is applied to achieve reliable parallel operation, then information exchange requirement is reduced, but output voltage accuracy deteriorates
Solution Approach 1:
The patent dynamically changes droop control parameters (slope, offset, and characteristics) based on operating conditions such as load level, battery state of charge, and converter temperature. By adjusting these parameters in real-time, the system maintains voltage accuracy across varying operating points while preserving the reliability benefits of droop-based parallel operation.
Data Source
AI summary
A power conversion device that converts DC power input from a DC power supply and outputs the DC power, the power conversion device including: an output current value acquisition unit acquiring an output current value; an output voltage value acquisition unit acquiring an output voltage value; and a controller controlling an output voltage. The controller includes a correction value generator configured to generate an output current correction value, based on an output current target value that is a target value of an output current, and the output current value, and a droop controller configured to droop an output voltage target value that is a target value of the output voltage, based on a corrected output current value that is the output current value corrected using the output current correction value. The output voltage is controlled based on the output voltage target value dropped and the output voltage value.