Diode Clamp Three-Level DAB Converter Reduces Current Stress
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Solution Overview
Problem
Traditional two-level dual active bridge converters face challenges with high current stress and low energy transmission efficiency, especially when port voltage varies over a wide range, necessitating improved conversion efficiency and reduced current root mean square (RMS) values across the voltage range.
Innovation Solution
A diode clamp mixed three-level dual active full-bridge converter with a four-degree-of-freedom global optimal control method, incorporating input and output filter capacitors, fully controlled switching devices, and a controller that adjusts duty ratios and phase shifts to minimize current stress and RMS values through the high-frequency isolation transformer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional two-level DAB converter is used, then the structure is simple, but the current stress and current RMS value are large when port voltage varies within a large range
Solution Approach 1:
The patent divides the single full-bridge converter into two separate full-bridge converters operating in parallel, each handling different voltage ranges. This segmentation allows each converter to operate in its optimal efficiency range, reducing overall current stress and RMS values while maintaining structural simplicity.
Solution Approach 2:
The patent implements dynamic switching between two-level and three-level operation modes based on the instantaneous port voltage. The converter dynamically adjusts its topology and control parameters to maintain optimal performance across the wide voltage range, reducing current stress and RMS values adaptively.
2Device complexity
If traditional two-level DAB converter is used, then the structure is simple, but the energy transmission efficiency is low when port voltage varies within a large range
Solution Approach 1:
The patent segments the operating voltage range into multiple zones, with each full-bridge converter optimized for specific voltage ranges. This allows the system to maintain high transmission efficiency across the entire voltage range by always operating in the optimal efficiency zone, significantly reducing energy losses.
Solution Approach 2:
The patent dynamically changes operating parameters including duty ratio, phase shift angle, and switching frequency based on the instantaneous port voltage. These parameter adjustments optimize the transmission efficiency at each operating point, minimizing energy losses while maintaining simple converter structure.
3Loss of energy
If diode clamp mixed three-level DAB converter is used, then the conversion efficiency is improved, but the control complexity increases due to multiple independent control variables
Solution Approach 1:
The patent segments the control of two full-bridge converters, with each converter having its own independent control loop. This segmentation simplifies the overall control complexity by dividing the multi-variable control problem into two separate, more manageable control problems, while still achieving improved conversion efficiency.
Solution Approach 2:
The patent implements self-service control where each full-bridge converter automatically adjusts its own operating parameters based on the instantaneous voltage conditions. This autonomous control approach reduces the coordination complexity between converters while maintaining optimal conversion efficiency across the wide voltage range.
Data Source
AI summary
A diode clamp mixed three-level dual-active full-bridge converter based on a dual active full-bridge converter, an additional control variable is added by replacing two-level bridge arm on the primary side with a diode clamp three-level bridge arm. A control method based on four variables including duty ratios of 0 voltage level and high voltage level of the primary side, duty ratio of 0 voltage level of the secondary side of the diode clamp mixed three-level dual active full-bridge converter, and phase shift ratio between primary and secondary sides of the diode clamp mixed three-level DAB converter; four-degree-of-freedom globally optimized control is realized by coordinating four variables, RMS value of the current is reduced, and operating efficiency of the converter is improved. Closed-loop control of the DAB globally optimized operation is given, which enables the converter to automatically realize globally optimized operation under different operating conditions.