Dual Active Bridge Control Using GHA for Wide Voltage Range
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Solution Overview
Problem
Conventional control methods for DC-DC converters, such as dual active bridge converters, suffer from inefficiencies due to inaccuracies in fundamental-harmonic-approximation (FHA) models when operating with large phase-shifted angles, particularly in applications like electric vehicle charging where output voltage varies widely.
Innovation Solution
Implementing hybrid optimized control using a generalized harmonic approximation (GHA) model to determine target duty ratios, phase shifts, and switch control signals for dual active bridge converters, optimizing control variables to minimize primary winding current and ensure efficient operation across a wide output range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fundamental-harmonic-approximation (FHA) model is used for control, then control simplicity is maintained, but control accuracy deteriorates when operating with large phase-shifted angles
Solution Approach 1:
The patent transitions from the fundamental-harmonic-approximation (FHA) model to a generalized harmonic approximation (GHA) model that incorporates higher odd-order harmonics (3rd, 5th, 7th, etc.). This parameter change in the mathematical model allows accurate representation of waveforms under large phase-shifted angle conditions, resolving the accuracy issue while maintaining computational feasibility through pre-calculated lookup tables.
2Device complexity
If conventional control methods are used, then device simplicity is maintained, but power conversion efficiency deteriorates during operation with large phase-shifted angles
Solution Approach 1:
The patent pre-calculates optimal control variables (duty ratios and phase shifts) for various operating conditions and stores them in lookup tables before actual operation. During runtime, the controller simply retrieves pre-optimized values based on current output voltage, avoiding complex real-time calculations and ensuring optimal power conversion efficiency without increasing operational complexity.
Solution Approach 2:
The patent implements dynamic adjustment of control parameters (duty ratios and phase shifts) based on output voltage levels. By changing these parameters according to the operating point and retrieving optimized values from lookup tables, the system maintains high power conversion efficiency across varying load conditions while avoiding the energy losses associated with conventional fixed-parameter control methods.
3Adaptability or versatility
If output voltage is allowed to vary widely for electric vehicle charging applications, then adaptability to different charging stages is improved, but control performance deteriorates with conventional methods
Solution Approach 1:
The patent implements dynamic control that adapts to different operating conditions by selecting appropriate control variables from lookup tables based on the current output voltage level. This allows the converter to optimize performance across different charging stages (constant current, constant power, constant voltage) while maintaining reliable control through pre-calculated optimal parameters for each operating region.
Data Source
AI summary
Systems and methods for controlling a dual active bridge converter or other type of DC-DC converter are disclosed herein. An output voltage of the dual active bridge converter is detected. Based at least in part on the output voltage, a first target duty ratio of a primary bridge of the dual active bridge converter and a second target duty ratio of a secondary bridge of the dual active bridge converter are retrieved from a table. Based on the output voltage, a target phase shift between the primary bridge and the secondary bridge is determined. Based on the first target duty ratio, the second target duty ratio, and the target phase shift, a plurality of switch control signals is caused to be provided to respective switches of the primary bridge and the secondary bridge, to switch according to a time-based switching sequence.