Power Converter Semiconductor Degradation Diagnosis by Constant Voltage
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Solution Overview
Problem
Existing diagnostic methods for electric power converters require the generation of short-circuit currents to determine the degradation state of semiconductor elements, which is not feasible due to the restricted allowed time for such currents.
Innovation Solution
A diagnostic apparatus and method that control the operations of semiconductor elements in an electric power converter to perform constant voltage outputs, allowing the determination of semiconductor element degradation based on the current flowing through the electric motor without generating short-circuit currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If short-circuit current is generated to determine semiconductor element degradation, then degradation detection capability is improved, but safety and operational reliability deteriorate due to severely restricted allowed time
Solution Approach 1:
The patent changes the electrical parameters from short-circuit current conditions to constant voltage output conditions. By setting the output voltage to a predetermined constant value and measuring the resulting current, the system achieves degradation detection without the safety risks associated with short-circuit currents. This parameter transformation allows accurate measurement of semiconductor element characteristics while maintaining operational safety.
2Measurement precision
If short-circuit current method is used for diagnosis, then degradation state determination is improved, but diagnosis time is reduced to severely restricted allowed time
Solution Approach 1:
The patent transforms the diagnostic approach from time-critical short-circuit current measurement to steady-state constant voltage measurement. By controlling the output voltage to a predetermined value and measuring the current under these stable conditions, the system eliminates the severe time restrictions while maintaining accurate degradation state determination capability.
3Reliability
If constant voltage output is used for diagnosis, then operational safety is improved, but degradation detection capability must be maintained equivalent to short-circuit current method
Solution Approach 1:
The patent employs feedback control by comparing the measured current under constant voltage output with predetermined threshold values. The control apparatus receives the current value, compares it against stored thresholds, and determines degradation states based on these comparisons. This feedback mechanism ensures accurate degradation detection while maintaining the safety benefits of constant voltage operation.
Solution Approach 2:
The patent applies a predetermined constant voltage that is sufficient to elicit measurable current responses for degradation detection without exceeding safe operational limits. By using just enough voltage to achieve accurate measurement while staying within safety boundaries, the system maintains both operational safety and degradation detection capability.
Data Source
AI summary
In an embodiment, a diagnostic apparatus of an electric power converter is provided, and the electric power converter outputs a converted AC electric power to an electric motor, thereby driving the electric motor. The diagnostic apparatus includes an output control unit and a degradation determination unit. The output control unit controls operations of semiconductor elements of the electric power converter, thereby outputting electric power from the electric power converter to the electric motor by constant voltage output, which constantly sets an output voltage to the electric motor in a target voltage pattern. The degradation determination unit determines a degradation state for at least one of the semiconductor elements based on a current flowing through the electric motor in the constant voltage output.