Dual Active Bridge Phase-Shift Control for Circulating Current Elimination
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Solution Overview
Problem
DAB converters face significant circulating power issues due to voltage mismatches between the primary and secondary sides, leading to increased current stress, converter losses, and design complexity, compromising cost-effectiveness and reliability.
Innovation Solution
A non-circulating-current phase-shift control method that limits the phase-shift ratios within a feasible region (Xf) to eliminate circulating current, ensuring zero-voltage turn-on and zero-current turn-off for switches, and optimizing phase-shift ratios for minimum losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If phase-shift control is used in DAB converters, then bidirectional energy transmission and electrical isolation are achieved, but circulating power increases when voltages are mismatched
Solution Approach 1:
The patent changes the control parameters by introducing a voltage-matched phase-shift control strategy. When voltage mismatch is detected, the system adjusts the phase-shift ratio dynamically and introduces an auxiliary phase-shift control to maintain optimal operating conditions, thereby reducing circulating power while preserving bidirectional energy transmission capability
Solution Approach 2:
The patent implements a feedback mechanism that continuously monitors the voltage mismatch condition and adjusts the phase-shift control parameters accordingly. The control system detects circulating power levels and modifies the switching phases to minimize circulating current, creating a closed-loop control that adapts to varying voltage conditions
2Adaptability or versatility
If circulating power is present, then voltage mismatch tolerance is improved, but current stress and converter losses increase
Solution Approach 1:
The patent dynamically changes control parameters based on voltage mismatch severity. When moderate voltage mismatch occurs, the system tolerates it with adjusted phase-shift ratios. When severe mismatch is detected, the system actively compensates by introducing auxiliary control signals that reduce circulating current, thereby maintaining voltage mismatch tolerance while minimizing converter losses
3Adaptability or versatility
If circulating power is present, then voltage mismatch accommodation is improved, but device cost and cooling requirements increase
Solution Approach 1:
The patent uses feedback control to monitor voltage mismatch conditions and activate compensation mechanisms only when necessary. The system detects circulating power levels and selectively applies phase-shift adjustments, avoiding the need for complex protection circuitry that would be required if circulating power were always present. This reduces device complexity while maintaining voltage mismatch accommodation
4Reliability
If circulating power is present, then voltage mismatch resilience is improved, but thermal management complexity increases
Solution Approach 1:
The patent dynamically adjusts phase-shift control parameters to minimize circulating power under varying voltage mismatch conditions. By actively controlling the operating parameters to reduce circulating current, the system maintains voltage mismatch resilience while significantly reducing heat generation, thereby simplifying thermal management requirements
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves high-efficiency and stable operation by eliminating circulating current, reducing switching losses, and enhancing the reliability and performance of DAB converters.
Implementation Method 1
The transformer provides galvanic isolation between the primary and secondary circuits via magnetic coupling
Data Source
AI summary
The present invention relates to a non-circulating-current phase-shift control method and system for a dual-active-bridge (DAB) converter. This method addresses the issue of circulating power arising from voltage mismatch between the primary and secondary sides of the DAB converter, which otherwise results in increased current stress, higher power losses, and elevated system costs. To eliminate circulating current, the proposed control strategy constrains the ratio between 1-D1 and 1-D3, denoted as a, based on the primary-side and secondary-side voltages as well as the transformer turns ratio. A normalized transmitted power Y is then calculated, and the optimal set of phase-shift ratios D1, D2 and D3 is selected to minimize both switching and conduction losses under non-circulating-current power transfer, thereby enabling high-efficiency operation. The method further ensures zero-voltage turn-on for all switches and zero-current turn-off for half of the switches, significantly reducing switching losses.