High-Voltage DC Converter Shutdown for Vehicle Insulation Faults
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Solution Overview
Problem
Existing high-voltage on-board power supplies in vehicles are prone to insulation faults that can lead to overloading the varistor in the DC charging station, causing damage to the ground potential line and resulting in faulty charging interruptions due to the inability to detect insulation faults quickly and effectively.
Innovation Solution
Incorporating a varistor with a low-impedance state triggered at a lower voltage than the DC charging station's design voltage, coupled with a current measuring device and processing unit to rapidly switch off DC converters and activate isolating elements when current intensity exceeds predefined limits, thereby limiting the short-circuit current and preventing varistor overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a DC converter is used to charge the traction battery at a DC charging station with lower charging voltage than battery voltage, then cost-effective and space-saving solution is achieved, but insulation faults can cause overloading of the varistor in the DC charging station leading to damage
Solution Approach 1:
The patent implements preliminary protective action by installing a varistor in parallel with the DC converter before insulation faults can occur. This varistor is specifically selected with voltage and energy parameters that enable it to clamp overvoltages and limit currents during insulation faults, preventing damage to the DC charging station's ground potential line while allowing normal charging operation
Solution Approach 2:
The patent introduces a varistor as an intermediary protective element between the DC converter and the DC charging station's ground potential line. This varistor acts as a mediator that absorbs and limits fault currents during insulation events, protecting both the vehicle's DC converter and the charging station's vulnerable ground potential line from damage
2Reliability
If the varistor in the DC charging station is designed with clamping voltage of 500V to protect insulation, then insulation protection is achieved, but the ground potential line in the charging cable is destroyed due to excessive current
Solution Approach 1:
The patent carefully selects the varistor's electrical parameters (voltage rating, energy capacity, clamping characteristics) to achieve optimal protection. The varistor is designed to clamp at a voltage level that protects insulation while its energy rating ensures it can limit the total fault current to levels that the ground potential line can withstand, thus changing the parameters of protection to balance both requirements
3Productivity
If insulation faults are not detected quickly, then system operation continues, but varistor overload and damage occur
Solution Approach 1:
The patent implements a feedback-based protection system where current sensors continuously monitor the DC converter's operation. When insulation faults occur, the system detects the abnormal current conditions through these sensors and provides feedback to the control unit, which then activates the protective varistor and shuts down the DC converter to prevent damage while maintaining system awareness
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
Enables rapid and interference-free detection of insulation faults, preventing varistor and ground potential line damage by limiting voltage and current, allowing for smaller isolating elements and contactors, and ensuring fault-free charging.
Implementation Method 1
the varistor is designed in such a way that it switches to the low-impedance state when a predetermined voltage, which is lower than a design voltage of, for example, 500V of the vehicle-external DC charging station
Implementation Method 2
a series connection comprising a varistor and a current measuring device is arranged between the other high-voltage potential line and the reference potential line
Data Source
AI summary
A DC converter is arranged in one of the high-voltage potential lines of a vehicle having a high-voltage on-board power supply. A series connection of a varistor and a current measuring device is arranged between the other high-voltage potential line and the reference potential line. A processing unit switches off the DC converter if a current intensity measured by the current measuring device exceeds at least one predetermined limit value. Alternatively, a DC converter is arranged in each of the two high-voltage potential lines, and a series connection having a varistor and a current measuring device is arranged between each of the high-voltage potential lines and the reference potential line. A processing unit switches off the DC converters if a current intensity measured by at least one of the current measuring devices exceeds at least one predetermined limit value.