EV Charging Device DC Residual Current Detection
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Solution Overview
Problem
Type A residual current circuit breakers in charging devices for high-voltage vehicle batteries are unable to detect DC residual currents, posing a safety risk as they cannot trigger a shutdown in response to these undetectable currents.
Innovation Solution
Incorporating a residual current detection device within the charging device that modifies the characteristic of DC residual currents to make them detectable by a Type A residual current circuit breaker, such as disabling the power factor correction filter or using a residual current monitor to change the current's characteristics, allowing the circuit breaker to trigger a shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a Type A residual current circuit breaker is used in the charging device, then the device complexity and cost are reduced, but the ability to detect DC residual currents is lost
Solution Approach 1:
The patent introduces an intermediary device (current characteristic modification unit) that transforms DC residual current into AC residual current. This intermediary component bridges the gap between the Type A circuit breaker's limitation (cannot detect DC) and the safety requirement (must detect all residual currents), allowing the simpler Type A breaker to effectively protect against DC leakage by converting it to a detectable AC signal.
Solution Approach 2:
The patent changes the parameter of residual current from DC to AC through the current characteristic modification unit. By altering the current type parameter, the system enables Type A circuit breakers (which only detect AC) to respond to DC residual currents, thus maintaining detection reliability while using simpler protection devices.
2Reliability
If a Type B residual current circuit breaker is used to detect DC residual currents, then the detection capability is improved, but the device complexity and cost increase significantly
Solution Approach 1:
Instead of upgrading to a complex Type B circuit breaker, the patent uses an intermediary current characteristic modification unit that converts DC residual current to AC. This intermediary approach achieves the same detection goal with simpler Type A breakers, avoiding the complexity and cost of Type B devices while maintaining full detection capability.
Solution Approach 2:
The patent creates a transformed copy of the residual current signal by converting DC to AC characteristics. This copied AC signal can be detected by standard Type A breakers, effectively replicating the detection capability of Type B breakers without requiring the more complex and expensive Type B hardware.
3Reliability
If the power factor correction filter is disabled to change residual current characteristics, then the detectability of DC residual current is improved, but the power factor correction function is lost
Solution Approach 1:
The patent dynamically controls the power factor correction filter, switching it between active and inactive states based on detection needs. The filter is activated during normal operation for power factor correction and deactivated when residual current detection is required, allowing the system to adapt its configuration to achieve both power efficiency and safety detection.
Solution Approach 2:
The system employs periodic monitoring and conditional deactivation of the power factor correction filter. The residual current detection device periodically checks for leakage currents, and when DC residual current is detected, the filter is temporarily deactivated to enable proper detection, then reactivated after the hazard is eliminated, creating a periodic cycle of activation and deactivation.
Data Source
AI summary
A charging device for a high-voltage battery of a motor vehicle, in particular a charging device installed in a motor vehicle, can be connected to an alternating current network via a connection device, which includes a residual current circuit breaker that does not detect a residual current of at least one residual current type, in particular a DC residual current. The charging device further includes a controllable component and a residual current detector for detecting a residual current of the residual current type, wherein the residual current detector controls the component to change the characteristic of the residual current in such a way that the residual current can be detected with the residual current circuit breaker.