Dual Active Bridge Converter Control for Wide-Range Power Flow
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Solution Overview
Problem
Conventional dual active bridge (DAB) DC/DC converters exhibit poor performance at wide input/output and load conditions, leading to sluggish transient response, poor tracking, and low stability margins, particularly due to limitations in modulation schemes like phase-shift-modulation (PSM) at low or medium power levels, which result in current spikes and transformer saturation.
Innovation Solution
A control system with a cascaded structure using a geometric-sequence-control (GSC) method, where the inner loop compensator samples the transformer current every half switching cycle, determining control parameters to adjust switching instants and prevent transformer saturation by switching between phase-shift modulation (PSM), variable duty cycle modulation (VDM), and triangular current mode modulation (TCM) based on power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If phase-shift modulation (PSM) is used for controlling DAB converters, then the simplicity of control is improved, but the performance at low or medium power loads deteriorates
Solution Approach 1:
The patent implements dynamic modulation scheme selection that adapts the control method based on the operating power level. At high power levels, PSM is used for simplicity; at low or medium power levels, the system automatically switches to alternative modulation schemes to maintain performance. This dynamic adaptation resolves the contradiction by making the control system flexible rather than fixed.
Solution Approach 2:
The patent changes the modulation scheme parameter based on power level conditions. By monitoring the operating point and switching between different modulation strategies (PSM at high power, alternative schemes at low/medium power), the system optimizes both simplicity and performance across the entire operating range.
2Stability of the object's composition
If conventional linear control techniques are used, then the stability at fixed operating point is improved, but the performance over wide input/output and load conditions deteriorates
Solution Approach 1:
The patent transitions from static linear control optimized for a single operating point to dynamic control that adapts to varying operating conditions. The system continuously monitors input/output voltages and load conditions, adjusting control parameters and modulation schemes accordingly to maintain stability and performance across wide ranges.
Solution Approach 2:
The patent creates a universal control system that can handle multiple operating conditions effectively. By incorporating multiple modulation schemes and adaptive control logic, the system achieves both the stability of linear control at fixed points and the versatility needed for wide-ranging input/output and load conditions.
3Ease of manufacture
If half cycle symmetry is used in modulation schemes, then the simplicity of implementation is improved, but current spikes and transformer saturation occur
Solution Approach 1:
The patent applies preliminary anti-action by detecting operating conditions that could lead to current spikes and transformer saturation, then preemptively adjusting the modulation scheme or control parameters to prevent these harmful effects before they occur. The system monitors power levels and switches away from half-cycle symmetric schemes when they would cause problems.
Solution Approach 2:
The patent dynamically adjusts the modulation approach based on real-time operating conditions. Rather than rigidly applying half-cycle symmetry, the system adapts the modulation strategy to prevent current spikes and saturation while maintaining implementation feasibility through structured decision logic.
Data Source
AI summary
Control system and method for controlling power flow in dual active bridge converters. The control system comprises a compensator, a feedback unit, and a modulator. An outer loop provides a reference signal. The output of the compensator are the control parameters for the modulator. The feedback unit samples the transformer current once every half switching cycle to thereby determine a power level. The power level is used to determine a modulation technique to apply. The modulation technique is one of phase-shift modulation (PSM), variable duty cycle modulation (VDM), or triangular current mode modulation (TCM).