Rotary Machine Control Device Switching Element Fault Detection
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Solution Overview
Problem
Existing control devices for rotary electrical machines in vehicles face challenges in accurately determining switching element faults due to rapid rotation and torque variations, as well as noise in phase current detection, leading to potential erroneous fault determinations.
Innovation Solution
A control device and method that includes a phase current detection unit, a phase current ratio derivation unit, and an element fault determination unit to assess the ratio of phase currents and determine fault status based on established threshold values, allowing for accurate identification of switching element faults without relying on DC component analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC component analysis is used to determine switching element faults, then fault detection capability is provided, but measurement precision deteriorates due to offset from rapid rotation/torque variations and noise
Solution Approach 1:
The invention changes the parameter used for fault detection from DC component magnitude to the ratio relationship between positive and negative half-wave currents. This parameter transformation eliminates the influence of offset caused by rapid rotation and torque variations, as well as noise interference, while maintaining the ability to detect switching element faults. The ratio parameter inherently normalizes the measurement, making it insensitive to absolute value shifts.
2Reliability
If element shorting determination circuits are installed in switching elements, then shorting fault determination capability is improved, but device complexity increases and self-fault detection capability is lost
Solution Approach 1:
The invention extracts the fault detection function from the switching elements themselves and relocates it to the control device. By analyzing the ratio relationship between positive and negative half-wave currents at the control device, the system determines switching element faults without requiring additional determination circuits within the switching elements, thereby reducing device complexity while maintaining detection capability.
Solution Approach 2:
The control device performs multiple functions: it controls the inverter operation and simultaneously detects switching element faults by analyzing current waveforms. This multi-functional approach eliminates the need for separate determination circuits, reducing overall system complexity while maintaining comprehensive monitoring capability.
3Measurement precision
If additional sensors are installed to improve fault detection accuracy, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses existing phase current detection circuits to perform dual purposes: normal control operations and fault detection. By analyzing the ratio relationship between positive and negative half-wave currents from the existing sensors, the system achieves accurate fault detection without requiring additional sensors, thereby avoiding increased device complexity and cost.
Data Source
AI summary
The control device for a rotary electrical machine which is connected between a DC power source and a rotary electrical machine and which controls driving of the rotary electrical machine by converting DC power from the DC power source into AC power, includes a power conversion circuit which is configured from a plurality of switching elements, a phase current detection unit which detects phase currents in the rotary electrical machine, a phase current ratio derivation unit which derives a ratio in which the phase currents detected by the phase current detection unit are equal to or greater than a reference value, or equal to or lower than the reference value, and an element fault determination unit which determines a fault status of each of the switching elements when the ratio derived by the phase current ratio derivation unit is equal to or greater than a previously established ratio threshold value.