Hybrid Five-Level Bidirectional DC/DC Converter Topology
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Solution Overview
Problem
Conventional two-level DAB converters face inefficiencies in energy transmission due to high current stress and RMS current values when dealing with ultra-wide port voltage ranges, such as those encountered in vehicle-mounted power battery applications, even with optimized modulation technologies.
Innovation Solution
A hybrid five-level bidirectional DC/DC converter topology with a primary-side hybrid five-level unit, a secondary-side single-phase full bridge, and a high-frequency isolation transformer, along with a voltage match modulation method using a PI controller to optimize duty ratios and phase shifts, reducing current stress and improving efficiency across the voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two-level DAB converter uses conventional modulation modes (SPSM, DPSM, EPSM, TPSM), then the converter can operate with bidirectional power flow and high power density, but when the voltage transmission ratio deviates from 1, the current stress and RMS current value increase significantly, reducing transmission efficiency
Solution Approach 1:
The primary-side bridge arm is segmented into a five-level unit and a two-level half-bridge unit. The five-level unit generates voltage levels of ±Vin/4, ±Vin/2, ±3Vin/4, while the two-level unit generates ±Vin/2. This segmentation allows independent regulation of duty ratios for each unit, enabling precise control of the voltage transmission ratio across ultra-wide ranges and maintaining low current stress and high efficiency throughout the operating range.
Solution Approach 2:
The converter employs dynamic duty ratio regulation for both the five-level unit (Dp0, Dp2, Dp3, Dp4) and the two-level unit (Ds0, Dss), allowing real-time optimization of the voltage transmission ratio. This dynamic control enables the system to adapt to varying voltage conditions and maintain optimal efficiency across the entire operating range, preventing current stress from increasing unnecessarily.
2Adaptability or versatility
If the voltage transmission ratio is far from 1 in a two-level DAB converter, then the converter can still operate, but the current stress and RMS current value become larger, requiring larger semiconductor devices and reducing overall performance
Solution Approach 1:
By dividing the primary-side bridge arm into five-level and two-level units with independently regulatable duty ratios, the system can precisely control the voltage transmission ratio even at extreme operating points. This prevents excessive current stress and RMS values, allowing the use of smaller, less complex semiconductor devices while maintaining adaptability across ultra-wide voltage ranges.
3Adaptability or versatility
If a hybrid five-level unit is added to the primary side, then the converter can achieve ultra-wide voltage range adaptation with optimized current stress, but the device complexity and number of semiconductor devices increase
Solution Approach 1:
The primary-side bridge arm is divided into a five-level unit and a two-level half-bridge unit. This segmentation provides independent duty ratio control for each unit, enabling precise voltage transmission ratio regulation across ultra-wide ranges while managing current stress effectively. The modular structure allows flexible configuration to achieve the desired voltage range coverage.
Solution Approach 2:
The system changes the voltage levels from two-level to five-level on the primary side, creating intermediate voltage levels (±Vin/4, ±Vin/2, ±3Vin/4) that enable finer control of the voltage transmission ratio. This parameter change allows the converter to maintain low current stress and high efficiency across an ultra-wide voltage range, achieving better adaptability despite increased structural complexity.
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 hybrid five-level converter significantly reduces current stress and RMS values, enhancing power conversion efficiency and adapting to ultra-wide voltage ranges, while also reducing semiconductor device count and system losses.
Implementation Method 1
a primary-side hybrid five-level unit, a primary-side two-level half bridge, a secondary-side single-phase full bridge H2, a high-frequency isolation transformer M1
Data Source
AI summary
The present disclosure discloses a hybrid five-level bidirectional DC/DC converter and a voltage match modulation method thereof. The converter includes a first input filter capacitor Cinp and a second input filter capacitor Cinn, an output filter capacitor Co, a DC voltage source, a primary-side hybrid five-level unit, a primary-side two-level half bridge, a secondary-side single-phase full bridge H2, a high-frequency isolation transformer M1, a high-frequency inductor Ls, and a controller. A positive pole of a DC bus of the primary-side hybrid five-level unit is coupled to a positive pole of the corresponding DC voltage source and to a positive pole of the input filter capacitor Cinp respectively. A negative pole of the DC bus of the primary-side hybrid five-level unit is coupled to a negative pole of the corresponding DC voltage source and to a negative pole of the input filter capacitor Cinn respectively. A terminal of the primary-side hybrid five-level unit is coupled to a midpoint between the first input filter capacitor Cinp and the second input filter capacitor Cinn connected in series. The primary-side hybrid five-level unit is coupled to a primary side of the high-frequency isolation transformer M1 through the high-frequency inductor Ls, and a midpoint of the primary-side two-level half bridge is coupled to another terminal of the primary side of the high-frequency transformer.