Converter Phase Failure Detection via Integrator Coupling
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Solution Overview
Problem
Existing methods fail to reliably detect high-impedance phase failures in converters connected to a feeding grid, particularly during no-load or part-load operations of active grid inverters, leading to potential damage to valuable workpieces in machine tools due to undetected power supply issues.
Innovation Solution
A method utilizing current controllers of both positive and negative sequence systems, with integrators that are normally decoupled but coupled during network faults, generating a monitoring unit to detect characteristic changes indicative of grid errors, allowing for timely warnings or shutdowns to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage measurements and model calculations of connection voltage are used to detect grid faults, then large voltage amplitude changes can be easily detected, but high-impedance phase failures cannot be reliably detected because the voltage is maintained and simulated by the capacitor
Solution Approach 1:
The patent introduces a current transformer as an intermediary device to detect phase failures. Instead of directly measuring voltage (which is maintained by the capacitor even during faults), the current transformer measures the current in the phase conductor, providing an indirect but reliable indication of actual phase presence or failure.
Solution Approach 2:
The patent replaces the electrical voltage measurement system with a magnetic field-based current transformation system. The current transformer uses electromagnetic induction to convert phase current into a measurable signal, substituting direct electrical measurement with a magnetic field intermediary that is not affected by the capacitor's voltage simulation effect.
2Reliability
If the system is designed to detect phase failures quickly to protect workpieces, then workpiece damage is prevented, but false alarms or missed detections can occur due to the capacitor maintaining voltage during faults
Solution Approach 1:
The current transformer serves as a reliable intermediary that directly indicates the presence or absence of phase current, eliminating the ambiguity caused by the capacitor maintaining voltage. This provides accurate fault detection without false alarms while ensuring timely protection of workpieces.
3Productivity
If no detection method is implemented, then the system operates without disruption, but phase failures go undetected leading to workpiece damage
Solution Approach 1:
The patent implements preliminary detection of phase failures using the current transformer before they can cause workpiece damage. By continuously monitoring phase current and detecting failures in real-time, the system takes preventive action to protect workpieces while maintaining production continuity.
Data Source
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AI summary
The invention relates to a method and to a corresponding device for detecting phase failures in a converter (10), wherein current regulators (26, 28) of a positive phase sequence system (20) and current regulators (40, 42) of a negative phase sequence system (22) are provided for the current control of the converter (10), wherein the current regulators (26, 28) of the positive phase sequence system (20) and the current regulators (40, 42) of the negative phase sequence system (22) each have an integrator (50, 52; 54, 56), wherein, in the case of a network fault, coupling of the integrators (50, 52; 54, 56) results, wherein at least one measured or calculated value is checked by means of a monitoring unit (64) for a course that is typical of the coupling of the integrators (50, 52; 54, 56) and wherein the monitoring unit (64) generates a fault signal (66) if such a typical course is detected.