Resonant EV Charger Control for Low-Loss 400V/800V Charging
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Solution Overview
Problem
Existing EV charging systems face challenges with high switching losses, inefficiencies, and inadequate power factor correction, particularly in high-voltage battery systems, leading to heat generation and reduced reliability in dynamic power delivery.
Innovation Solution
A super-twisting sliding mode controller (ST-SMC) is integrated with an AC/DC transformer-based converter to achieve zero-voltage switching (ZVS) and zero-current switching (ZCS) for primary and secondary side switches, utilizing a current-fed resonant converter with an active clamp and voltage doubler circuit for efficient power factor correction and voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional AC/DC converters with diode bridge rectifier are used for EV charging, then power conversion can be achieved, but switching losses become significant and power quality deteriorates
Solution Approach 1:
The patent replaces conventional mechanical switching devices with resonant switching mechanisms that operate at higher frequencies with lower losses. The resonant converter topology substitutes traditional diode bridge rectification with a resonant tank circuit that achieves soft switching, eliminating hard switching losses and improving overall conversion efficiency while maintaining power quality standards
Solution Approach 2:
The patent changes the operating parameters of the AC/DC converter by implementing resonant frequency operation instead of conventional fixed-frequency switching. By tuning the resonant tank circuit parameters (inductance and capacitance values) to operate at optimal resonant frequencies, the system achieves minimal switching losses and improved power factor correction while meeting IEC 61000-3-2 power quality requirements
2Speed
If higher voltage battery systems (800V) are implemented for faster charging, then charging speed improves, but switching losses and heat generation increase
Solution Approach 1:
The patent employs periodic resonant oscillations in the tank circuit to achieve soft switching at higher voltages. By synchronizing the switching actions with the resonant cycles of the tank circuit, the system maintains efficient power transfer at 800V charging levels while minimizing switching losses through zero-voltage switching (ZVS) and zero-current switching (ZCS) techniques
Solution Approach 2:
The resonant tank circuit acts as an intermediary between the high-voltage input and the battery charging output. This intermediate resonant stage buffers the high voltage transitions, allowing fast charging at 800V while the resonant oscillations smooth out the switching transients and reduce electromagnetic interference and switching losses
3Reliability
If power factor correction is improved in AC/DC converters, then power quality increases, but device complexity increases
Solution Approach 1:
The patent merges the power factor correction (PFC) function with the main AC/DC conversion process by integrating the resonant tank circuit to perform both functions simultaneously. The resonant converter topology inherently provides unity power factor operation while converting AC to DC, eliminating the need for separate PFC stages and reducing overall system complexity despite improved power quality performance
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 minimizes switching losses, enhances power factor, and ensures robust control against external perturbations, providing high efficiency and reliable power conversion for both 400V and 800V EV battery packs.
Implementation Method 1
charging, with current generated by a resonant inductor on the secondary side of the transformer, an output capacitor
Implementation Method 2
AC/DC transformer-based converter
Data Source
AI summary
A circuit and methods including super-twisting sliding mode controller (ST-SMC) control of an AC/DC quasi single-stage current-fed resonant converter for electric vehicle (EV) charging. The converter includes primary side switches and a secondary side bidirectional switch, achieving zero-voltage switching (ZVS) for efficient operation. The primary side includes an active clamp circuit, while the secondary side incorporates a resonant tank for smooth energy transfer. The ST-SMC generates pulse width modulation signals, ensuring ZVS at turn ON and turn OFF for primary switches, and ZVS at turn ON with low-voltage switching at turn OFF for the bidirectional switch. The circuit includes a feedback loop with an error calculation unit for precise control of grid current and output voltage, providing power factor correction and regulated output for 400V and 800V EV batteries.