Power Converter Fault Localization for Multi-Phase Ground Faults
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Solution Overview
Problem
Existing methods struggle to accurately determine ground fault locations when multiple phases of a motor experience faults close to each other, as they rely on current ratios that are not applicable in such scenarios.
Innovation Solution
A power conversion device and method that utilize current measurements and inductance calculations to differentiate between ground fault phases, allowing for precise determination of fault locations on both the motor and cables, even when multiple phases are affected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current ratio method is used to determine ground fault location, then ground fault location can be estimated for single phase faults, but the method fails when multiple phases have ground faults at close locations
Solution Approach 1:
The patent segments the ground fault diagnosis process into multiple measurement modes: single-phase ground fault measurement mode and two-phase ground fault measurement mode. By dividing the diagnosis approach based on fault type, the system can apply appropriate measurement methods for each scenario, resolving the limitation of the conventional current ratio method which only works for single-phase faults.
Solution Approach 2:
The patent changes the measurement parameters based on the fault condition. For single-phase ground faults, it measures ground fault current; for two-phase ground faults, it measures interphase short-circuit current. This parameter adaptation allows accurate location estimation for both fault types by selecting the appropriate current measurement and calculation method.
2Reliability
If conventional overcurrent detection is used, then protection against short circuit and ground fault can be achieved, but the user cannot specify whether the fault occurred on the cable or inside the motor
Solution Approach 1:
The patent implements feedback by measuring the actual current values during fault conditions and using these measurements to calculate fault location. The system provides feedback information to the user about whether the fault occurred on the cable or inside the motor, enabling informed decision-making for maintenance and repair operations.
Solution Approach 2:
The patent introduces an intermediary calculation process that uses measured current values and known inductance parameters to determine fault location. This intermediary step translates raw current measurements into meaningful location information, bridging the gap between fault detection and fault localization.
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 accurate identification and notification of ground fault locations on motors and cables, even when multiple phases are involved, enhancing fault diagnosis efficiency.
Implementation Method 1
the ground fault current measurement unit 121 turns on either all the switches (SWu, SWv, and SWw) of the upper arms or all the switches (SWx, SWy, and SWz) of the lower arms, measures a ground fault current
Data Source
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Figure 3(a)~3(c)
AI summary
It is an object to provide a power conversion device and a ground fault location diagnosis method for determining ground fault locations on a motor and a cable and notifying a user or an external device or system of a determination result even when ground faults of a plurality of phases occur at locations close to each other. In order to achieve the above object, the power conversion device includes a ground fault current measurement unit, an interphase short-circuit current measurement unit, and a ground fault location determination unit. The ground fault current measurement unit turns on all the switches of either upper arms or lower arms of three half-bridge circuits, and measures output current values of a plurality of phases generated during the ON period. The interphase short-circuit current measurement unit turns on a switch of an upper arm of one phase of the three half-bridge circuits and a switch of a lower arm of a phase different from the one phase, and measures output current values of a plurality of phases generated during a period of time for which both the switches are ON. The ground fault location determination unit determines a ground fault location based on the output current values measured by the ground fault current measurement unit and the output current values measured by the interphase short-circuit current measurement unit.