AC Motor Controller Modulation Ratio Adjustment for Sensor Failure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing AC rotating electric machine control systems face challenges in maintaining stable operation when a magnetic-pole position sensor failure occurs, particularly due to degradation in rotor angle estimation performance caused by harmonic waves during overmodulation control in sensorless vector control modes.
Innovation Solution
A controller for AC rotating electric machines that includes magnetic-pole position detecting and estimating circuitry, failure-state determining circuitry, rotation-information switching circuitry, and modulation-ratio switching circuitry to ensure reliable operation by adjusting the modulation ratio and switching control based on sensor failure states, thereby reducing harmonic effects and maintaining stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If overmodulation control is performed in sensorless vector control, then voltage utilization rate is improved, but estimation performance for rotor angle degrades due to harmonic wave effects
Solution Approach 1:
The patent changes the control parameter (modulation ratio) based on the operational state. When sensorless vector control is active, the modulation ratio is limited to prevent overmodulation and its harmful harmonic effects, while still allowing efficient operation within safe limits. This dynamic parameter adjustment resolves the contradiction between maximizing voltage utilization and maintaining estimation accuracy.
2Device complexity
If sensorless vector control is used to operate without magnetic-pole position sensor, then device complexity is reduced, but reliability deteriorates when sensor failure occurs due to degraded estimation performance
Solution Approach 1:
The patent prepares compensatory measures in advance by implementing specific control strategies when sensorless mode is detected. The controller activates alternative control algorithms and adjusts modulation ratios proactively when operating without sensor feedback, cushioning against the potential instability before it occurs. This ensures reliable operation even in sensor failure conditions.
Solution Approach 2:
The control system dynamically adapts its behavior based on the operational mode. When sensorless vector control is detected, the system automatically adjusts control parameters and algorithms in real-time, transitioning from standard control to failure-mode-appropriate control strategies, thereby maintaining reliability despite the absence of sensor feedback.
3Power
If modulation ratio is increased to improve voltage utilization, then power output is improved, but harmonic components increase causing estimation degradation
Solution Approach 1:
The patent dynamically adjusts the modulation ratio parameter based on the control mode and operational conditions. In sensorless vector control mode, the modulation ratio is constrained to remain below thresholds that would generate excessive harmonics, while still permitting high enough values to maintain adequate power output. This parameter optimization resolves the contradiction between power delivery and harmonic suppression.
Data Source
AI summary
In a controller for an AC rotating electric machine, a failure-state determining circuitry determines a failure state of a magnetic-pole position sensor based on an output signal from the magnetic-pole position sensor. A modulation-ratio switching circuitry outputs a target value of a modulation ratio and also changes the target value to be output based on a result of the failure-state determining circuitry. The modulation-ratio switching circuitry sets, when the magnetic-pole position sensor is determined as being abnormal by the failure-state determining circuitry, the target value to be smaller than in a case in which the magnetic-pole sensor is determined as being normal by the failure-state determining circuitry.