Inverter Control Device Voltage Clamping for Stability
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Solution Overview
Problem
Existing motor control systems experience instability due to significant pulse width variation in PWM signals when an abnormality is detected in the direct-current voltage detection means, leading to loss of control stability.
Innovation Solution
The inverter control device stabilizes operations by clamping the detected voltage at a second assured voltage higher than the first assured voltage, determined based on the upper limit of the assured voltage range, when an abnormality is detected in the voltage detection means, thereby reducing pulse width variation and maintaining control stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reference voltage is clamped at the lowest value when an abnormality is detected, then the inverter can operate with a safety margin, but the pulse width variation becomes great and control stability is lost
Solution Approach 1:
The patent changes the reference voltage parameter from the lowest assured voltage to a higher voltage value within the assured voltage range when an abnormality is detected. This parameter change allows the system to maintain control stability while still operating within safe margins, as the higher reference voltage reduces pulse width variation in PWM signals.
Solution Approach 2:
The patent implements dynamic adjustment of the reference voltage based on the detection of abnormalities. When no abnormality is detected, the lowest assured voltage is used; when an abnormality is detected, the reference voltage is switched to a higher value. This dynamic adaptation resolves the contradiction by adjusting the operating point according to system conditions.
2Stability of the object's composition
If the reference voltage is increased to reduce pulse width variation, then control stability improves, but the safety margin for inverter operation decreases
Solution Approach 1:
The patent carefully selects a higher voltage value within the assured voltage range as the new reference voltage, rather than using the maximum possible voltage. This controlled parameter change improves control stability while maintaining an adequate safety margin, as the selected voltage remains within the assured operating range.
Solution Approach 2:
The system dynamically switches between two reference voltage levels based on abnormality detection status. This dynamic approach allows the system to optimize for control stability when needed while maintaining safety margins through the careful selection of the higher voltage level within the assured range.
Data Source
Figure 1
AI summary
An inverter control device comprising: a voltage detection means for detecting the direct-current voltage of an inverter (6) that converts a direct-current power input from a direct-current power supply into an alternating-current power; a target value calculation means for calculating a target value of an alternating current output from the inverter (6) based on a detection voltage detected by the voltage detection means; an inverter control means for generating a control signal for a switching element involved in the inverter (6) based on the detection voltage and the target value to control the inverter (6); an abnormality detection means for detecting the occurrence of an abnormality in the voltage detection means; and a voltage clamp means for clamping a detection voltage to be used for calculating the target value at a first assured voltage and a detection voltage to be used for generating a control signal is clamped at a second assured voltage that is higher than the first assured voltage when the abnormality is detected by the abnormality detection means, wherein the first assured voltage is determined based on the lower limit area of an assured voltage range that assures the performance of the inverter (6).