Inverter Current Sensor Abnormality Detection via Auxiliary Energization
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Solution Overview
Problem
Existing power conversion devices face challenges in detecting abnormalities in current detection values, particularly due to zero fixation issues caused by short circuits in shunt resistors, which can lead to unintended behavior of rotating electric machines and uncomfortable assist torque in electric power steering systems.
Innovation Solution
A power conversion device is designed with an energization unit that can energize a sensor without passing through the inverter, allowing for detection of zero fixation abnormalities by ensuring non-zero current detection values even when high or low potential side switching elements are off, thereby distinguishing normal and abnormal states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a shunt resistor is disposed on the bus of the inverter for current detection, then current detection is enabled, but the shunt voltage may be fixed to zero due to short circuit making abnormality undetectable
Solution Approach 1:
An auxiliary switching element is introduced as an intermediary component to enable abnormality detection. This auxiliary switching element provides an alternative current path through the shunt resistor that is independent of the inverter switching elements, allowing the control unit to actively test the shunt resistor's functionality and detect short circuit conditions that would otherwise be undetectable
2Ease of operation
If current detection value is zero in normal state, then the system operates normally, but abnormality (zero fixation) cannot be discriminated from normal operation
Solution Approach 1:
The control unit performs preliminary abnormality detection by actively energizing the shunt resistor through the auxiliary switching element before normal operation proceeds. This preliminary action establishes a known non-zero current state that allows the system to verify the shunt resistor's health and distinguish it from normal zero-voltage operating conditions
3Reliability
If shunt voltage is zero during normal operation, then the inverter functions correctly, but zero fixation abnormality cannot be distinguished from normal state
Solution Approach 1:
The control unit implements periodic abnormality detection by cyclically activating the auxiliary switching element to pass current through the shunt resistor. This periodic action creates intermittent non-zero voltage states that allow continuous monitoring and distinction between normal operation (persistently zero voltage) and abnormality (inability to generate voltage even during activation periods)
Data Source
AI summary
A power conversion device includes: an inverter that includes high potential side switching elements connected to a high potential side and low potential side switching elements connected to a low potential side, and converts a current for supplying a rotating electric machine; a current detector having a sensor disposed on at least one of a positive bus for connecting the high potential side switching elements and a positive side of a DC power supply or a negative bus for connecting the low potential side switching elements and a negative side of the DC power supply; an energization device that energizes the sensor without passing through the inverter; and a controller that acquires a current detection value from the current detector, and controls the inverter and the energization device. The energization device energizes the sensor when all of high or low potential side switching elements are off.