Dual Active Bridge Ripple Cancellation via Phase-Shifted Segmentation
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Solution Overview
Problem
Dual active bridge converters face significant challenges due to high ripple current demands on the output capacitor, which becomes a constraint as power levels increase in aerospace applications, necessitating a solution to reduce or eliminate ripple current.
Innovation Solution
The implementation of a dual active bridge system with multiple DABs sharing common capacitors and a control module that controls the H-bridges to commutate diagonal switches at a 50% duty cycle and phase shifts the power flow between the first and second sides of each DAB by 180 degrees to cancel ripple current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If dual active bridge converter is used for power conversion in aerospace applications, then power conversion capability is improved, but output capacitor ripple current increases to levels comparable with output current
Solution Approach 1:
The patent divides a single high-power DAB converter into multiple parallel DAB converters (e.g., two or more). Each DAB handles a portion of the total power, and their ripple currents are phase-shifted relative to each other. This segmentation allows the ripple currents to partially cancel out when combined, reducing the total ripple current stress on the output capacitor while maintaining the required power conversion capability.
Solution Approach 2:
The patent employs phase-shifted periodic switching of the parallel DAB converters. By controlling the switching cycles of each DAB to be offset in phase (e.g., 180 degrees out of phase), the ripple current waveforms from each converter are temporally distributed. This periodic phase shifting causes the peak ripple currents to occur at different times, allowing them to cancel each other out when combined, thereby reducing the overall ripple current magnitude.
2Power
If power levels are increased for more electric aircraft and electric propulsion, then power conversion power level is improved, but output capacitor becomes even more impractical due to technological limits
Solution Approach 1:
The patent segments the high-power conversion task across multiple parallel DAB converters. This segmentation inherently distributes the ripple current stress, allowing the use of smaller, more practical output capacitors that are within current technological limits. Each capacitor in the parallel configuration handles a reduced portion of the total ripple current, making the overall system practical for high-power aerospace applications.
Solution Approach 2:
The patent converts the harmful effect of ripple current into a beneficial cancellation effect. By deliberately phase-shifting the operation of parallel DAB converters, the harmful ripple currents from each converter are transformed into a system where the ripples cancel each other out. This converts what would normally be a limiting factor (ripple current) into an advantage, enabling the use of smaller, more practical capacitors at high power levels.
3Volume of stationary object
If multiple parallel DABs share common capacitors with ripple cancelation, then output capacitor size is reduced, but control complexity increases
Solution Approach 1:
The patent implements feedback control mechanisms to manage the phase shifting of parallel DAB converters. Sensors monitor the ripple current and power flow conditions, and the control system adjusts the switching phases of each DAB in real-time to maintain optimal ripple cancellation. This feedback ensures that the capacitors remain smaller while the control complexity is managed through automated adjustment rather than manual tuning.
Solution Approach 2:
The patent dynamically changes operating parameters (switching phases, duty cycles) of the parallel DAB converters to optimize ripple cancellation. By continuously adjusting these parameters based on load conditions and power flow requirements, the system maintains reduced capacitor sizes across varying operating conditions. The control complexity is managed through parameter optimization algorithms that balance ripple cancellation with power conversion efficiency.
Data Source
AI summary
A dual active bridge system can include a plurality of dual active bridges (DABs). Each DAB can have a first side connected in parallel and a second side connected in parallel such that each of the plurality of DABs share a common first side capacitor and a common second side capacitor. The plurality of DABs can be configured to be operated to reduce or eliminate ripple current at the first side capacitor and/or second side capacitor.