On-board Charger Frequency Modulation for Battery Charging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
On-board chargers (OBCs) for electric and plugin hybrid electric vehicles take 4 to 6 hours to charge batteries using commercial AC power, and high-speed chargers have variable DC output, leading to inefficiencies and longer charging times.
Innovation Solution
A battery charging method and system that controls the output voltage of a first converter based on the battery load voltage and rated voltage, applying it to a second converter for frequency modulation using low-speed or high-speed frequency modulation methods to generate a frequency harmonic in the battery current, optimizing charging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-speed battery charger supplies variable DC power, then charging speed is improved, but system complexity and control difficulty increase
Solution Approach 1:
The charging system is divided into two separate converters: a first converter that performs power factor correction and converts AC to DC, and a second converter that performs voltage conversion and frequency modulation. This segmentation allows each converter to specialize in specific functions, improving overall charging speed while managing system complexity through functional decomposition.
Solution Approach 2:
The patent implements dynamic control by adjusting the output voltage of the first converter based on battery load voltage states and using frequency modulation in the second converter. The system dynamically switches between low-speed and high-speed frequency modulation methods based on real-time battery conditions, enabling adaptive charging that improves speed while maintaining controllability.
2Loss of energy
If output voltage is controlled based on battery load voltage state, then charging efficiency is improved, but control complexity increases
Solution Approach 1:
The patent implements feedback control by continuously monitoring the battery load voltage and comparing it with the rated voltage. Based on this feedback, the controller adjusts the output voltage of the first converter and selects appropriate frequency modulation methods for the second converter. This feedback mechanism reduces switching losses by optimizing voltage control according to actual battery conditions while managing control complexity through systematic decision logic.
Solution Approach 2:
The system changes operating parameters dynamically by adjusting the output voltage of the first converter based on the ratio of battery load voltage to rated voltage. When the load voltage is less than rated voltage, the output voltage is increased to a first voltage; when equal to or greater than rated voltage, it is adjusted to a second voltage. This parameter change strategy reduces energy losses while maintaining manageable control complexity through clear voltage thresholds.
3Productivity
If frequency modulation is performed using high-speed method, then charging speed is improved, but current ripple increases
Solution Approach 1:
The patent dynamically selects between low-speed and high-speed frequency modulation methods based on real-time battery conditions. The controller monitors the battery load voltage state and switches modulation speeds accordingly, enabling the system to achieve high charging speed when conditions permit while reducing current ripple when necessary, thus balancing productivity with harmful factor reduction.
Solution Approach 2:
The system changes the modulation speed parameter based on the ratio of battery load voltage to rated voltage. When the ratio indicates favorable conditions, high-speed frequency modulation is applied to maximize charging speed. When the ratio suggests potential issues, the system switches to low-speed modulation to reduce current ripple. This parameter change strategy allows flexible optimization of both charging speed and current quality.
Data Source
AI summary
A battery charging method for an on-board charger (OBC) includes: applying, by a controller, an output voltage of a first converter to a second converter by controlling the output voltage based on a result of a comparison between a battery load voltage and a battery rated voltage; controlling, by the controller, the second converter to perform a frequency modulation on the output voltage using a low-speed frequency modulation method or a high-speed frequency modulation method based on a result of the control of the output voltage; and generating, by the controller, a frequency harmonic of a system frequency in a battery current based on a modulation method used to perform the frequency modulation. An output voltage of the first converter is controlled based on a load voltage state of a battery and applied to the second converter.