Dual Active Bridge Current Control for Lower Peak and RMS Currents
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Solution Overview
Problem
Conventional dual active bridge DC/DC converters face challenges with high peak and RMS currents through the transformer, leading to increased switching power loss and higher device ratings, necessitating significant cooling and higher ratings for switching devices, transformers, and inductors.
Innovation Solution
The Fundamental Harmonic Matching Control Technique (FHMT) optimizes the operation of dual active bridge DC/DC converters by comparing and matching the first harmonics of voltages across the transformer, determining an adjustment factor and phase shift angle to reduce peak currents in the inductor, thereby reducing the current ratings of switching devices, transformers, and inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional dual active bridge control is used, then bidirectional power flow capability is achieved, but high peak current and RMS current flow through the transformer
Solution Approach 1:
The patent applies parameter changes by modifying the control parameters of the dual active bridge converter. Specifically, it uses phase-shift control where the phase difference between primary and secondary bridge switching signals is adjusted to regulate power flow. This continuous adjustment of timing parameters enables bidirectional power flow while optimizing current waveforms to reduce peak and RMS currents through the transformer.
Solution Approach 2:
The patent employs periodic switching action in both primary and secondary full-bridge circuits. By synchronizing the switching frequencies of both bridges and introducing a controllable phase shift between them, the system achieves bidirectional power flow control. The periodic nature of the switching waveforms, when properly phased, creates controlled current flow patterns that reduce peak currents while maintaining versatile power transfer capability.
2Power
If high instantaneous voltage drop across the inductor is present, then power transfer is achieved, but high switching power loss occurs in the switching devices
Solution Approach 1:
The patent reduces switching power loss by optimizing the timing parameters of voltage application across the inductor. By controlling the phase shift between primary and secondary bridges, the inductor voltage waveform is shaped to minimize abrupt transitions and reduce the magnitude of voltage drops during switching events. This parameter optimization maintains effective power transfer while reducing switching losses in the semiconductor devices.
3Power
If high peak current is present, then power transfer capability is maintained, but device ratings of switching devices, transformer, and inductor must be rated for high current
Solution Approach 1:
The patent optimizes device ratings by changing the temporal distribution of current through phase-shift control. Instead of having high peak currents, the system uses optimized phase relationships to distribute current more evenly over time. This parameter optimization allows the same power transfer capability with lower peak current demands, enabling the use of switching devices, transformer, and inductor with lower current ratings while maintaining full power transfer capability.
Data Source
AI summary
A fundamental harmonic matching control technique (FHMT) can optimize the use of the switching devices needed to operate a dual active bridge DC/DC converter, which reduces the peak and RMS currents thereby reducing the switching power losses. The FHMT control techniques can also reduce the current rating of the switching devices, transformer, and the inductor of the dual active bridge DC/DC converter.