Inverter Control for Multiphase Motor Short-Circuit Detection
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Solution Overview
Problem
Existing electronic control devices for multiphase motors, such as those used in EPS systems, face challenges in detecting intersystem short-circuits without increasing the processing load on the controller, particularly when no potential difference appears between PWM outputs, leading to undetected short-circuit currents.
Innovation Solution
The solution involves an electronic control device with inverter circuits for each system, where upper or lower arm switching elements of all phases in one system are turned ON, and the corresponding elements in the other system are turned OFF, allowing for current detection and determination of power supply failures based on current values, thereby detecting intersystem short-circuits without increasing the processing load on the controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current detection is performed at the midpoint of low output period for A/D conversion, then normal motor control operation is maintained, but intersystem short-circuit cannot be detected when no potential difference appears between PWM outputs
Solution Approach 1:
The controller proactively creates a potential difference between the two PWM output systems by inverting the PWM carrier phase, enabling short-circuit detection to be performed at the standard current detection timing without requiring additional processing or specialized timing windows.
Solution Approach 2:
The PWM carrier signals of the two systems are configured with inverted phases, creating periodic potential differences between systems. This periodic inversion ensures that during certain phases of the PWM cycle, a detectable potential difference exists for short-circuit detection, while maintaining normal dual-system motor control operation.
2Reliability
If dual inverter systems are provided to cover failure of one system, then system reliability is improved, but intersystem short-circuit causes output interference that hinders desired control
Solution Approach 1:
The two inverter systems are configured with asymmetric PWM carrier phases (inverted relative to each other), which creates a detectable distinction between the systems. This asymmetry enables the controller to identify intersystem short-circuits by detecting abnormal current patterns that occur when the asymmetric potential differences cause unexpected current flow between systems.
Solution Approach 2:
The controller continuously monitors current detection values from both inverter systems and compares them against expected values. When an intersystem short-circuit occurs, the feedback mechanism detects the abnormal current patterns caused by potential difference interference, allowing the controller to identify and respond to the fault condition.
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
This approach enables reliable detection of intersystem short-circuits without increasing the processing load on the controller, ensuring continuous motor control operations and preventing sudden stops of assisted steering.
Implementation Method 1
setting different voltage values for a center voltage of a pulse width modulation (PWM) signal output from an inverter of a first system and that output from an inverter of a second system
Implementation Method 2
allow a larger amount of current to flow from the inverter of the first system to the inverter of the second system upon intersystem short-circuit
Data Source
AI summary
Provided is an electronic control device including inverter circuits of first and second systems for driving a multiphase motor with first and second coil sets by use of upper and lower arm switching elements selectively controlled to be ON/OFF in each coil of the first and second coil sets. The upper arm switching elements of all phases in the inverter circuit of the first system are turned ON to apply a high potential to the first coil set, and the lower arm switching elements of all phases in the inverter circuit of the second system are turned ON to control the second coil set to a low potential. When a value of current flowing through the lower arm switching element in the inverter circuit of the second system is a predetermined value or more, it is determined that a power supply failure has occurred between the first and second systems.