EV Charger Reducing Low-Frequency Leakage Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Charging apparatuses for electric vehicles face issues with low-frequency leakage current due to common-mode components in non-symmetric AC power sources, leading to premature stoppage of charging when the leakage current exceeds detection levels set by Residual Current Detection devices.
Innovation Solution
A charging apparatus is designed with a power factor correction converter and a DC-DC converter, featuring a second duty controller that determines a duty value to cancel out common-mode components by adjusting the voltages of Y-capacitors connected to the output terminal, ensuring they are half the voltage of the energy storage device, thereby reducing low-frequency leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a Y-capacitor is connected to the output terminal to remove noise components, then noise filtering is improved, but low-frequency leakage current increases due to common-mode component
Solution Approach 1:
The patent introduces a common-mode voltage detection unit and a duty cycle adjustment unit that act as intermediaries between the Y-capacitor and the common-mode component. The detection unit monitors the common-mode voltage, and the adjustment unit modifies the switching duty cycle to compensate for the common-mode component, thereby reducing leakage current while preserving the noise filtering function of the Y-capacitor
Solution Approach 2:
The patent changes the operating parameters of the power factor correction converter by dynamically adjusting the duty cycle of the switching element. By detecting the common-mode voltage and modifying the duty cycle accordingly, the system alters the electrical parameters to cancel out the common-mode component, reducing leakage current through the Y-capacitor while maintaining noise filtering performance
2Loss of energy
If the DC-DC converter is made non-insulating type to improve efficiency, then power conversion efficiency is improved, but common-mode component flows out as leakage current
Solution Approach 1:
The patent implements a feedback mechanism where the common-mode voltage detection unit continuously monitors the common-mode voltage at the output terminal and feeds this information back to the duty cycle adjustment unit. The adjustment unit then modifies the switching duty cycle in real-time to compensate for the common-mode component, creating a closed-loop control system that reduces leakage current while maintaining the efficiency benefits of the non-insulating DC-DC converter
Data Source
AI summary
A charging apparatus capable of reducing low-frequency leakage current includes: a power factor correction converter including a switch, wherein the power factor correction converter converts an AC power inputted by an on/off control of the switch into a DC power by correcting a power factor of the AC power; a DC-DC converter changing a magnitude of voltage outputted from the power factor correction converter into a magnitude of voltage required by an energy storage device to be charged; a first duty controller determining a first duty value of the switch for outputting a voltage having a predetermined magnitude through the power factor correction converter based on a magnitude of a differential mode component of the AC power; and a second duty controller determining a second duty value of the switch for removing a common-mode component of the AC power based on the common-mode component.