Inverter Phase Failure Detection via DC Link Voltage Ratio

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Solution Overview

Problem

Existing drive device controllers face challenges in reliably detecting phase failures due to voltage fluctuations, which can lead to unreliable error signal generation and increased hardware and software efforts for threshold detection and evaluation.

Innovation Solution

A method and apparatus that filter the rectified voltage to detect signal components at the double frequency of the mains frequency, determining a ratio signal of the average link voltage to the signal component, and comparing it with an error threshold to generate an error detection signal, with the threshold defined as a percentage to be independent of the current mains voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If absolute threshold values are used for error detection, then simple detection is achieved, but adaptability to different mains voltages is reduced

Engineering Contradiction:

Improvevoltage independenceVSAvoidthreshold definition complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent transforms the detection parameter from absolute voltage values to a dimensionless ratio signal. This parameter change enables universal applicability across different mains voltage systems without requiring voltage-specific threshold calibration, achieving voltage independence while simplifying the threshold definition to a single universal value.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The ratio-based detection method serves as a universal solution for phase failure detection across different mains voltage systems (e.g., 230V, 400V, 480V). The same detection algorithm and threshold apply universally, eliminating the need for system-specific threshold adjustments and enhancing the adaptability of the detection device.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If bandpasses are used for error detection, then phase failure detection is achieved, but device complexity increases

Engineering Contradiction:

Improvephase failure detectionVSAvoidhardware and software efforts

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts only the essential frequency components (fundamental wave and double frequency component) from the rectified voltage signal using spectral analysis. By focusing on these specific components and forming their ratio, the method achieves phase failure detection without requiring complex bandpass filters or extensive signal processing hardware, reducing device complexity while maintaining detection reliability.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS10386426B2Detecting a failure of a phase in a grid for inverters having a frequency detection in an intermediate DC voltage link

Publication Date: 2019.08.20 SCHMIDHAUSER AG

AI summary

A detection of a failure of a phase (as a method and apparatus) in a system—supplied by multiple phases—including a DC link (5) is suggested. A rectified voltage (10) of the DC link (5) pulses at a multiple of the mains frequency as a fundamental wave. The rectified voltage (10) is filtered for detecting a signal component at the double frequency of the mains frequency (12). The rectified voltage (10) is also “filtered” for detecting an average link voltage (14). A ratio signal (17) is formed as a ratio of the average link voltage (14) to the signal component at the double frequency of the mains frequency (12). An error detection signal (19) results from a comparison of the ratio signal (17) with an error threshold (20).