Power Converter Filter with Shared Neutral Inductance

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Solution Overview

Problem

Conventional filters for power converters in power networks require neutral current to pass through inductors on the neutral lines, increasing cost and insertion loss, which is undesirable for applications with circuit protection and protective multiple earth systems where low impedance is necessary for safety.

Innovation Solution

A filter design where the neutral inductance is shared between the input and output sections and not in-line with the neutral line, using a common-mode filter configuration with inductors wound on a common core, and a differential-mode filter configuration, allowing for reduced inductor count and lower insertion loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If neutral current passes through inductors on the neutral line in conventional filters, then EMC filtering is achieved, but insertion loss increases and cost increases

Engineering Contradiction:

ImproveEMC complianceVSAvoidinsertion loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent extracts the neutral inductance from the neutral line and relocates it to the live lines. The filter neutral terminal is decoupled from the physical neutral line, allowing neutral current to bypass the inductors while maintaining EMC filtering functionality through the live line inductors.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The inductors on the live lines serve dual functions: they provide common-mode filtering for EMC compliance and also handle the neutral current return path. This multi-functionality eliminates the need for separate neutral line inductors, reducing insertion loss while maintaining filtering effectiveness.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If neutral current passes through inductors on the neutral line in conventional filters, then filtering is provided, but the number of inductors increases cost

Engineering Contradiction:

ImproveEMC complianceVSAvoidfilter cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent merges the neutral current handling function with the live line inductors. By providing a filter neutral terminal that connects to live lines rather than the physical neutral line, the design consolidates multiple inductor functions into fewer components, reducing material costs and manufacturing complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The live line inductors perform multiple functions including common-mode filtering and neutral current return path, eliminating the need for separate neutral line inductors and reducing overall component count and cost.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If neutral inductance is placed in-line with the neutral line, then common-mode filtering is achieved, but impedance in the neutral line increases affecting safety

Engineering Contradiction:

ImproveEMC filteringVSAvoidneutral line impedance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts the neutral inductance from the neutral line path and relocates it to the live lines. The filter neutral terminal provides a virtual neutral reference that does not physically connect to the neutral line through inductors, thereby maintaining low impedance in the actual neutral line for safety while achieving EMC filtering through alternative paths.

Inventive Principle:

Principle #2Taking out (Extraction)

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

This design reduces the number of inductors required, minimizes insertion loss, and allows for smaller neutral inductor current handling, enhancing EMC compliance and safety by avoiding increased impedance in the neutral line.

Implementation Method 1

the first input inductance, the first output inductance and the first neutral inductance are wound on a common core

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

an input section having a first input inductance provided at an input of the power converter; an output section having a first output inductance provided at an output of the power converter

Methodology Applied

Scientific EffectMagnetic energy storage: Inductor

Data Source

PatentUS10298113B2Filter for a power network

Publication Date: 2019.05.21 HTIP

AI summary

A filter for a power converter provided in-line with at least one live line of a power network. The filter has an input section with an input inductance provided at an input of the power converter and an output section with an output inductance provided at an output of the power converter. A neutral inductance provided between the power converter and a neutral line of the power network such that the neutral inductance is not in-line with the neutral line of the power network. The neutral inductance is shared by the input section and the output section.