Supertwisting Sliding Mode Control for ZVS EV Charging Converters
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Solution Overview
Problem
Current EV charging systems face challenges in optimizing power conversion efficiency, managing heat production, and providing robust control against external perturbations, leading to significant switching losses and power quality issues, especially with the transition to higher voltage batteries like 800V systems.
Innovation Solution
A super-twisting sliding mode controller (ST-SMC) is implemented in an AC/DC transformer-based converter, which generates pulse width modulation signals for primary and secondary side switches to achieve zero-voltage switching, reducing switching losses and enhancing power factor correction and voltage regulation, while maintaining a fixed duty ratio to minimize input current ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sliding mode control is used in EV charging systems, then robust control against perturbations is achieved, but chattering occurs leading to increased switching losses and reduced efficiency
Solution Approach 1:
The patent extracts and eliminates the chattering component from the control signal by introducing a filtering mechanism that separates the useful control action from the harmful high-frequency oscillations, thereby reducing switching losses while maintaining robust control performance
Solution Approach 2:
The patent modifies the control parameters by implementing a variable switching frequency approach and adjusting the sliding mode gain dynamically based on system conditions, which reduces unnecessary switching actions and minimizes switching losses while preserving control robustness
2Productivity
If higher voltage batteries (800V) are used to reduce charging time, then charging speed is improved, but switching losses and heat production increase significantly
Solution Approach 1:
The patent implements dynamic voltage and current regulation that adapts switching parameters in real-time based on the charging state and load conditions, optimizing the balance between charging speed and switching losses for 800V battery systems
Solution Approach 2:
The patent employs periodic pulse width modulation with optimized duty cycles that reduce the frequency of high-loss switching events while maintaining the required power transfer rate for fast charging applications
3Stability of the object's composition
If fixed duty ratio control is applied, then input current ripples are minimized, but voltage regulation under varying load conditions deteriorates
Solution Approach 1:
The patent applies preliminary filtering and predistortion techniques to the control signal that anticipate and compensate for voltage droop under load changes, maintaining stable output voltage while preserving the low ripple characteristics of fixed duty ratio operation
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 achieves high-frequency operation with reduced switching losses, enhanced efficiency, and unity power factor correction, effectively addressing the inefficiencies and heat management issues in existing EV charging systems for both 400V and 800V battery architectures.
Implementation Method 1
generate pulse width modulation signals which switch a polarity of the plurality of primary side switches with zero-voltage switching error at turn ON and at turn OFF
Implementation Method 2
an AC/DC transformer-based converter including a plurality of primary side switches and a secondary side bidirectional switch
Implementation Method 3
charging, with current generated by a resonant inductor on the secondary side of the transformer, an output capacitor
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.