Single-Stage On-Board Charger PFC Control for Reduced Capacitor Size
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Solution Overview
Problem
Current single-stage on-board chargers for electric vehicles face challenges in meeting new ISO standards due to high-power requirements, leading to bulky capacitors that reduce power density and increase costs, while also failing to effectively compensate for component tolerances and light-load conditions.
Innovation Solution
The implementation of a single-stage on-board charger system with a pulsating buffer converter and dual active bridge topology, which reduces the size of energy storage capacitors and includes a controller to compensate for undetected current portions, enabling efficient power transfer and compliance with updated ISO standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-power requirements are implemented to meet new ISO standards, then power delivery capability is improved, but capacitor size increases and power density decreases
Solution Approach 1:
The patent divides the single-stage OBC into modular converter units, each handling a portion of the total power conversion. This segmentation allows the system to meet high-power requirements through parallel operation of multiple smaller modules rather than requiring a single large-capacitor-based high-power converter, thereby reducing individual capacitor sizes while maintaining total power delivery capability.
Solution Approach 2:
The patent transitions from traditional bulk-capacitor-based power smoothing to a pulsating buffer converter approach that operates at higher frequency. By changing the time dimension of operation (using high-frequency switching), the system can achieve the same power delivery with significantly reduced capacitor volume, as energy storage requirements are distributed over more frequent cycling events.
2Reliability
If traditional Power Factor Correction is used, then power factor is improved, but undetected current portions cause measurement errors and compliance issues
Solution Approach 1:
The patent implements a feedback mechanism where the controller continuously monitors the filtered input signal and compares it against expected values. When discrepancies are detected (indicating undetected current portions), the controller adjusts the switching signals to the active bridges to compensate for these errors, thereby maintaining accurate power factor correction despite the presence of undetected current components.
Solution Approach 2:
The patent introduces a pulsating buffer converter as an intermediary element between the main power conversion path and the measurement system. This buffer isolates the measurement system from the problematic undetected current portions while still allowing accurate power factor correction to be implemented through the controller's management of the buffer's operation.
3Device complexity
If single-stage OBC architecture is used, then device complexity is reduced, but component tolerance compensation becomes difficult
Solution Approach 1:
The patent implements self-service through the controller's ability to automatically detect and compensate for component tolerance variations. The system monitors its own performance parameters and adjusts switching signals in real-time to compensate for deviations caused by component tolerances, eliminating the need for external calibration or manual adjustment while maintaining the simplicity of the single-stage architecture.
Solution Approach 2:
The patent dynamically changes operating parameters (such as switching frequencies and duty cycles) to compensate for component tolerance variations. By adjusting these parameters in real-time based on feedback from the system's performance monitoring, the controller maintains optimal operation despite variations in component characteristics, all while preserving the simple single-stage architecture.
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
This solution enhances Power Factor Correction performance, reduces capacitor size requirements, and improves power density, while meeting new ISO standards by effectively managing component tolerances and light-load conditions.
Implementation Method 1
The least one transformer includes one or more primary windings and one or more secondary windings... generate a first voltage signal in response to a filtered input signal... generate a second voltage signal in response to the first voltage signal
Implementation Method 2
The filter is operably coupled to the first modular converter configured to provide the filtered input signal to the first modular converter... The filtered input signal includes a detectable current portion and an undetected current portion
Data Source
AI summary
In at least one embodiment, a vehicle battery charger is provided. The vehicle battery charger includes at least one transformer, a first modular converter, a filter, and at least one controller. The first modular converter includes a first plurality of switching devices to generate a first voltage signal in response to a filtered input signal. A second plurality of switching devices generate a second voltage signal. The filter is operably coupled to the first modular converter and provides the filtered input signal to the first modular converter in response to a first input signal from a mains supply. The filtered input signal includes a detectable current portion and an undetected current portion. The controller is programmed to determine the undetected current portion based at least on a capacitance of the filter and generate a first control variable to compensate for the undetected current portion.