Input-Side Ground Fault Detection in Power Conditioners

Solution Overview

Problem

Conventional power conditioners require a ground fault detector on the output side of the inverter circuit to accurately detect AC ground faults, leading to complex circuit configurations and increased space requirements.

Innovation Solution

A power conditioner with an inverter circuit, a voltage dividing circuit, and a ground fault detector on the input side that uses frequency filtering and voltage comparison to detect AC ground faults without relying on an overvoltage ground fault relay (OVGR) on the output side, allowing for separate detection of AC ground faults.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a ground fault detector is provided on the output side of the inverter circuit to accurately detect AC ground faults, then the detection accuracy is improved, but the circuit configuration becomes complicated and the installation space increases

Engineering Contradiction:

ImproveAC ground fault detection accuracyVSAvoidcircuit configuration complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the AC ground fault detection function into the input-side ground fault detector by combining frequency filtering and voltage comparison operations. The frequency filter extracts AC components from the input voltage signal, and the voltage comparison unit compares these filtered signals against reference potentials, thereby integrating multiple detection capabilities into a single device without requiring separate output-side detection circuitry.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The input-side ground fault detector is designed to perform multiple functions: it detects both DC ground faults (using the original voltage signal) and AC ground faults (using the frequency-filtered voltage signal). This multi-functionality eliminates the need for separate detection devices on the output side, simplifying the overall circuit configuration while maintaining comprehensive ground fault detection coverage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a ground fault detector is provided on the output side of the inverter circuit to detect AC ground faults, then the detection capability is improved, but the installation space increases

Engineering Contradiction:

ImproveAC ground fault detection capabilityVSAvoidinstallation space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent merges the AC ground fault detection function into the input-side ground fault detector by combining frequency filtering and voltage comparison operations. The frequency filter extracts AC components from the input voltage signal, and the voltage comparison unit compares these filtered signals against reference potentials, thereby integrating multiple detection capabilities into a single device without requiring separate output-side detection circuitry.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The input-side ground fault detector is designed to perform multiple functions: it detects both DC ground faults (using the original voltage signal) and AC ground faults (using the frequency-filtered voltage signal). This multi-functionality eliminates the need for separate detection devices on the output side, simplifying the overall circuit configuration while maintaining comprehensive ground fault detection coverage.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables the detection of AC ground faults on the input side of the inverter circuit, distinguishing between AC and DC ground faults based on waveform differences, thereby simplifying the circuit configuration and reducing space requirements.

Implementation Method 1

a frequency filter receiving an input voltage signal, passing a first voltage signal having a frequency equal to or higher than a predetermined first frequency, and blocking a signal having a frequency lower than the first frequency

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Implementation Method 2

a low pass filter receiving the input voltage signal, passing a second voltage signal having a frequency equal to or lower than a second frequency determined lower than the first frequency, and blocking a signal having a frequency higher than the second frequency

Methodology Applied

Scientific EffectLow pass filtering: Filter (electronic)

Implementation Method 3

a voltage comparison unit generating an AC ground fault detection signal when a deviation of the first voltage signal with respect to a predetermined AC ground fault reference potential is equal to or greater than a predetermined AC ground fault detection voltage

Methodology Applied

Scientific EffectVoltage comparison:

Data Source

PatentUS11177647B2Ground fault detector and power conditioner with input-side ground fault detection

Publication Date: 2021.11.16 TMEIC CORP

AI summary

A power conditioner includes an inverter circuit that converts a DC voltage into an AC voltage, a voltage dividing circuit having one end connected to the positive electrode input terminal and the other end connected to the negative electrode input terminal, and a ground fault detector configured to receive a voltage divided by the voltage dividing circuit as an input voltage signal and to detect an occurrence of a ground fault based on the magnitude of the voltage of the input voltage signal. the ground fault detector emits an AC ground fault detection signal when the input voltage signal includes a first voltage signal having a frequency equal to or higher than a predetermined first frequency and a deviation of the first voltage signal with respect to an AC ground reference potential is equal to or larger than an AC ground fault detection voltage.