Zero Current Detection Using Capacitive Phase Shift Compensation

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Solution Overview

Problem

Existing inverter systems used in charging stations for electric vehicles face challenges in accurately identifying zero-currents due to interference and harmonic superimposition, leading to inadequate control and reliability issues.

Innovation Solution

A circuit arrangement that employs a capacitor as the load to account for phase displacement, combined with a current converter, amplification unit, and digital processing unit to accurately identify zero-currents, eliminating interference and ensuring precise control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional current sensing methods are used in inverter systems, then the system can operate, but zero-current identification is inaccurate due to interference and harmonic superimposition

Engineering Contradiction:

Improvezero-current identification accuracyVSAvoidinterference and harmonic superimposition

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent extracts only the necessary information for zero-current detection by using a capacitor to integrate the alternating current, producing a voltage signal that directly indicates zero-crossings without containing harmful harmonics or interference components present in the original current waveform.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces a capacitor as an intermediary element between the alternating current source and the detection system. This capacitor converts the current signal into a voltage signal through integration, acting as a mediator that eliminates interference and harmonics while preserving the zero-crossing information.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If direct current measurement is used, then the measurement is straightforward, but interference and harmonics contaminate the zero-current detection

Engineering Contradiction:

Improveoperational reliabilityVSAvoidinterference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The capacitor serves as an intermediary that transforms the direct current measurement approach into an indirect voltage measurement approach. This intermediary element filters out interference and harmonics while transmitting the essential zero-crossing information, thereby improving reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces direct electrical measurement with a transformed measurement system using capacitive integration. This substitution changes the measurement domain from direct current sensing to voltage detection after capacitive transformation, eliminating the harmful effects of interference and harmonics.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If high frequency operation is implemented, then productivity increases, but zero-current identification becomes more difficult due to increased interference

Engineering Contradiction:

Improveoperating frequencyVSAvoidzero-current detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The capacitor acts as a frequency-independent intermediary that integrates current at any operating frequency. This allows the system to operate at high frequencies for improved productivity while the capacitor continuously transforms the current signal into a clean voltage signal for accurate zero-current detection regardless of frequency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the measurement parameter from direct current to voltage through capacitive integration. This parameter transformation allows the system to maintain accurate zero-current detection across a wide range of operating frequencies, enabling high-frequency operation without sacrificing measurement precision.

Inventive Principle:

Principle #35Parameter changes

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 solution enables the accurate and interference-free identification of zero-currents, enhancing the operational reliability of inverter systems and charging stations, even at high frequencies.

Implementation Method 1

the load comprises a capacitor (30) through which the alternating current or a measuring current derived therefrom can flow

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

an evaluation unit which is connected to the load in order to evaluate an electric voltage generated on the load through which the alternating current flows

Methodology Applied

Scientific EffectElectrical voltage generation: Electric Field

Data Source

PatentUS10232721B2Determining a zero current of an alternating current

Publication Date: 2019.03.19 SIEMENS AG

AI summary

A circuit arrangement for detecting a zero crossing of an alternating current is provided. The circuit arrangement includes a load through which the alternating current can flow, and an evaluation unit connected to the load and configured to evaluate an electrical voltage formed at the load, and to determining zero currents. The load comprises a capacitor through which the alternating current or a current to be measured derived therefrom can flow, and the evaluation unit is configured to account for a phase shift caused by the capacitor for determining the zero currents.