Multi-Port DC-DC Converter With Fixed-Frequency ZVS Control
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Solution Overview
Problem
Existing multiple-port DC-DC converters face challenges with increased losses and loss of zero voltage switching (ZVS) at low loads due to the use of additional components in LCL-T resonant circuits and variable frequency control in series resonant converters, and insufficient stored energy in dual-active bridge converters.
Innovation Solution
Implementing a multiple-port bidirectional DC-DC converter with fixed switching frequency operation, utilizing an LCL-T resonant circuit at least at one port and an SRC or DAB converter at another, allowing for simplified magnetic component design and achieving ZVS even at lighter loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If LCL-T resonant circuit is used in multiple-port DC-DC converter, then power transfer efficiency is improved, but device complexity increases due to additional components
Solution Approach 1:
The LCL-T resonant circuit is designed to serve multiple ports simultaneously, allowing a single resonant circuit structure to handle power transfer between multiple ports. This multi-functional approach improves power transfer efficiency across all ports while avoiding the need for separate resonant circuits for each port, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent combines the resonant circuit functionality across multiple ports by sharing common components. The LCL-T configuration merges inductors and capacitors into a unified resonant structure that benefits all connected ports, achieving efficient power transfer without proportionally increasing the number of components.
2Adaptability or versatility
If variable frequency control is used in series resonant converter, then adaptability is improved, but loss of zero voltage switching occurs at low loads
Solution Approach 1:
The patent implements dynamic control of switching frequency while maintaining the ability to achieve zero voltage switching. The controller dynamically adjusts the switching frequency based on load conditions, but ensures that ZVS is maintained across the operating range by coordinating the switching timing with the resonant tank voltage waveform, thus preserving reliability at low loads while maintaining adaptability.
Solution Approach 2:
The control system uses feedback from voltage and current sensors to monitor the resonant tank state and adjust switching frequency accordingly. This feedback mechanism ensures that zero voltage switching conditions are maintained by detecting when the tank voltage reaches zero and timing the switch activation appropriately, even as load conditions vary.
3Adaptability or versatility
If dual-active bridge converter is used, then bidirectional operation is achieved, but stored energy is insufficient
Solution Approach 1:
The patent changes the energy storage parameters by introducing an auxiliary inductor specifically dedicated to energy storage in the bidirectional power transfer path. This auxiliary inductor increases the available stored energy for bidirectional operation without altering the core DAB converter structure, thereby maintaining bidirectional capability while addressing the insufficient energy storage issue.
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 solution enables efficient power transfer with zero voltage switching (ZVS) at fixed frequencies, reducing losses and simplifying control, enhancing reliability and redundancy for applications like DC micro-grids, charging stations, and electric vehicles.
Implementation Method 1
a resonant circuit comprising a first inductor (L1), a capacitor (C), and a second inductor (L2) arranged in a 'T' configuration (LCL-T)
Implementation Method 2
a transformer that passes the AC signal by electromagnetic induction to a secondary side of the transformer
Implementation Method 3
achieving ZVS even at lighter loads
Data Source
AI summary
A DC-DC converter includes a first port at a primary side of a transformer including a primary-side converter with primary-side switches and a second port at a secondary side including a second port converter with second-port switches and a resonant circuit including a first inductor, a capacitor, and a second inductor in LCL-T arrangement. A third port at the secondary side includes a third port converter with third-port switches. A controller controls the primary-side switches, the second-port switches, and the third-port switches at fixed-frequency for operation in a first mode, in which the first port supplies power to the second port and the third port, in a second mode, in which the second port supplies power to the first port and the third port, or in a third mode, in which the second port supplies power to the third port while the first port is disconnected.