Intermediate-Circuit Power Converter for Leakage Current Suppression

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Solution Overview

Problem

Transformerless power converters for charging electric vehicles on single-, two-, or three-phase alternating current grids are costly due to the need for multiple power electronic stages, and leakage currents from parasitic capacitances can interfere with protective equipment.

Innovation Solution

A power converter with a controlled six-pulse bridge circuit and inductors to regulate voltages across capacitors, using switches to connect to different phases, and an active ripple filter to stabilize voltages, reducing complexity and preventing leakage currents.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple power electronic stages are used to achieve universal charging on single-, two-, or three-phase grids, then adaptability is improved, but device complexity and cost increase

Engineering Contradiction:

Improveadaptability to different grid typesVSAvoidnumber of power electronic stages

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The power converter is designed with a universal circuit topology that can operate on single-phase, two-phase, or three-phase alternating current grids using the same core components. The first power converter stage uses a bridge circuit configuration that adapts to different phase inputs, and the second stage uses a half-bridge circuit that universally converts to direct current output, eliminating the need for separate charging devices for different grid types.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The power converter is divided into two functional stages: a first power converter stage with a bridge circuit for alternating current conversion, and a second power converter stage with a half-bridge circuit for direct current conversion. This segmentation allows each stage to perform its specific function efficiently while working together to achieve universal grid compatibility.

Inventive Principle:

Principle #1Segmentation

2Ease of manufacture

If standard bridge circuits are used for power conversion, then ease of manufacture is improved, but leakage currents from parasitic capacitances increase

Engineering Contradiction:

Improvestandard circuit implementationVSAvoidleakage currents

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

A neutral conductor connection is introduced as an intermediary element connected to the midpoint of the capacitor half-bridge in the second power converter stage. This neutral conductor serves as a reference potential that stabilizes the circuit operation and prevents leakage currents by providing a defined return path for capacitive displacement currents, thereby eliminating the harmful effects of parasitic capacitances while maintaining standard bridge circuit topology.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12445040B2Bidirectional power converter having intermediate circuit

Publication Date: 2025.10.14 HELLA GMBH & CO KGAA

AI summary

A power converter including a three-phase alternating current input and output, a first power converter stage having a first input and output and a second input and output, an intermediate circuit, a second power converter stage having a first input and output and a second input and output and a direct current input and output, wherein the first input and output of the first power converter stage is electrically connected to the three-phase alternating current input and output, and the second input and output of the first power converter stage is electrically connected to the intermediate circuit.