Multiphase Chopper Failure Detection with Variable Drift Thresholds
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Solution Overview
Problem
Conventional power conversion devices face reduced detection accuracy of drift currents in multiphase transformer circuits when phase currents are small, leading to increased risk of erroneous failure detection.
Innovation Solution
A power conversion device with a multiphase transformer circuit that includes a current sensor for detecting phase currents, a drift current detection unit, and a failure determination unit capable of setting variable failure detection thresholds based on the state amount of the transformer circuit, reducing erroneous failure detection by comparing drift currents with these thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed failure detection threshold is used for drift current detection, then the detection method is simple, but detection accuracy decreases when phase current becomes small leading to erroneous failure detection
Solution Approach 1:
The patent applies dynamics by making the failure detection threshold variable rather than fixed. The threshold dynamically adapts based on the detected phase current magnitude, using different threshold values for different current ranges. This resolves the contradiction by maintaining high detection accuracy across varying current conditions while implementing a manageable complexity through predefined threshold ranges.
Solution Approach 2:
The patent changes the parameter of the detection threshold based on the phase current level. By dividing the current range into multiple levels and assigning different threshold values to each level, the system maintains accurate drift current detection regardless of whether the phase current is large or small, thus resolving the accuracy issue without excessive complexity.
2Reliability
If peak comparison method is used for drift current detection, then the detection process is straightforward, but erroneous detection increases when phase current is small
Solution Approach 1:
The patent applies local quality by tailoring the detection threshold to the local current condition. Instead of using a uniform threshold, the system selects different threshold values based on the detected phase current range, thereby improving reliability specifically in the small current region where erroneous detection previously occurred.
Solution Approach 2:
The detection system dynamically adjusts the threshold based on real-time current measurements. This dynamic adaptation improves reliability across varying operating conditions, particularly preventing erroneous detection during low current operation while maintaining the straightforward peak comparison detection method.
3Device complexity
If a single current sensor is used to detect total phase current, then the device configuration is simple, but individual chopper circuit current measurement is indirect
Solution Approach 1:
The patent makes the single current sensor multi-functional by using it to detect the total phase current that serves multiple purposes: it provides the basis for determining the operational state of the power conversion device and enables drift current detection for failure diagnosis. This universal usage maintains device simplicity while achieving the needed measurement precision through sophisticated signal processing.
Solution Approach 2:
The total phase current detected by the single sensor acts as an intermediary that carries information about the individual chopper circuit operations. By analyzing this intermediary measurement in conjunction with switching element state information, the system can indirectly but accurately assess individual circuit performance without requiring separate sensors for each circuit.
Data Source
AI summary
The purpose of the present invention is to provide a power conversion device capable of further decreasing, compared to the prior art, misdetection of failures in a chopper circuit which constitutes phases. In order to achieve the foregoing, the present invention comprises: a multi-phase transformer circuit in which a plurality of chopper circuits are connected in parallel according to the number of phases; a drift detection unit which detects drift in a phase current in each chopper circuit; and a failure detection unit which variably sets a failure threshold value according to a state quantity of the chopper circuit, and which detects a failure in the chopper circuit by comparing the drift with the failure threshold value.