RLC Filter for EV Charging Common Mode Current Diversion

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing electric vehicle charging systems face issues with high-frequency leakage currents caused by external disturbances, particularly from photovoltaic installations, which can lead to device malfunction and require heavy, expensive isolation transformers, and existing solutions are not fully satisfactory for common mode harmonic correction.

Innovation Solution

An electric charging device equipped with an RLC filter connected between neutral and earth, tuned to specific frequencies to divert common mode currents back to earth instead of allowing them to reach the charger, thereby eliminating the need for heavy isolation transformers and addressing common mode disturbances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an isolation transformer is used to block common mode leakage currents, then the charging station is protected from external disturbances, but the device becomes heavy, expensive, and non-extensible

Engineering Contradiction:

Improveprotection against common mode leakage currentsVSAvoidweight of isolation transformer

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The patent changes the electrical parameters by introducing an RLC filter circuit with specific resonance frequency tuned to block common mode currents at particular frequencies (e.g., 1650 Hz and 1950 Hz), replacing the heavy isolation transformer with a lightweight frequency-selective filtering approach that achieves protection without the mass and cost of traditional transformers

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary RLC filter circuit between the charging station and the power network that selectively blocks common mode currents while allowing normal charging operations, serving as a lighter alternative to the isolation transformer while maintaining protection functionality

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If an isolation transformer is used to block common mode leakage currents, then the charging station is protected from external disturbances, but the cost increases significantly

Engineering Contradiction:

Improveprotection against common mode leakage currentsVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the expensive, heavy isolation transformer with a more economical RLC filter circuit that uses standard electronic components (resistors, capacitors, inductors) to achieve the same protective function at lower cost, making the solution more accessible for charging station deployment

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If an isolation transformer is used to block common mode leakage currents, then protection is provided, but the charging station cannot be easily extended with additional charging points

Engineering Contradiction:

Improveprotection against common mode leakage currentsVSAvoidextensibility of charging station

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent segments the protection function into modular RLC filter circuits that can be independently applied to each charging point or phase, allowing the charging station to be easily extended with additional charging points without requiring a complete replacement of the protection system, unlike a monolithic isolation transformer approach

Inventive Principle:

Principle #1Segmentation

4Reliability

If existing harmonic correction solutions are used, then differential mode harmonics are corrected, but common mode disturbances from photovoltaic installations are not addressed

Engineering Contradiction:

Improvecorrection of voltage harmonicsVSAvoidcommon mode leakage currents

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by specifically targeting common mode currents at particular frequencies (1650 Hz and 1950 Hz) with tuned RLC filter circuits, rather than applying general harmonic correction to all differential mode harmonics, thereby addressing the specific harmful factor of common mode leakage currents from photovoltaic installations while allowing differential mode harmonics to be handled by existing correction systems

Inventive Principle:

Principle #3Local quality

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

The RLC filter effectively neutralizes high-frequency common mode currents, preventing them from reaching the vehicle charger and reducing the risk of device malfunction, while being more cost-effective and extensible than traditional solutions.

Implementation Method 1

an RLC filter by which common mode currents from an external disturbance source loop back instead of going to the charger

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentEP3235114B1Common mode filtering device

Publication Date: 2020.05.27 RENAULT SA

Figure 1~3

AI summary

The invention relates to an electrical device for charging a battery of an electric motor vehicle, said device including a charging station connected to a power grid via a transformer and intended for being connected to a charger (Cy) built into the motor vehicle capable of recharging the battery. The invention is characterised in that the electrical charging device includes at least one RLC filter (10), wherein common mode currents of an external interference source are looped back via the RLC filter rather than continuing to the charger.