Sensorless Motor Controller Using Negative Sequence Carrier Feedback
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Solution Overview
Problem
Existing sensorless rotor position detection systems in dynamoelectric machines face inaccuracies at low speeds due to unbalanced high-frequency carrier signals, which are caused by transistor dead-time and EMI filter variations, leading to incorrect estimation of rotor position and velocity.
Innovation Solution
A negative sequence feedback circuit is employed to monitor and correct unbalances in the high-frequency carrier voltage by converting it to negative sequence components, generating feedback, and modifying the carrier voltage to minimize unbalances, ensuring a balanced signal for accurate rotor position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-frequency carrier signal is injected into the dynamoelectric machine for sensorless rotor position detection, then rotor position detection capability is improved, but unbalances in the carrier signal cause incorrect estimation of rotor position and velocity
Solution Approach 1:
The patent implements a feedback mechanism where the injected carrier signal is monitored, converted to negative sequence components, and used to generate corrective feedback. This feedback is applied to modify the carrier signal generation, creating a closed-loop system that automatically corrects unbalances in real-time, thereby maintaining signal balance and detection accuracy
Solution Approach 2:
The patent dynamically adjusts the carrier signal parameters by converting the monitored carrier voltage to negative sequence components and using these components to modify the carrier signal characteristics. This parameter adjustment compensates for unbalances caused by transistor dead-time and EMI filter variations
2Ease of operation
If transistor dead-time and EMI filter variations are present in the inverter system, then system operation is enabled, but unbalances in the high-frequency carrier voltage are introduced
Solution Approach 1:
The system monitors the actual carrier voltage output and feeds back negative sequence components to correct unbalances caused by transistor dead-time and EMI filter variations, maintaining voltage balance despite these operational imperfections
Solution Approach 2:
The patent converts the harmful effect of unbalances (caused by dead-time and filter variations) into useful negative sequence feedback signals that automatically correct the unbalances, transforming system imperfections into correction mechanisms
Data Source
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AI summary
A negative sequence feedback circuit (26) is connected to monitor and minimize unbalances in a high-frequency ac carrier signal provided to a motor/load (22) for the purpose of detecting rotor position. The negative sequence feedback circuit detects unbalances in the high-frequency ac carrier signal and generates negative sequence feedback. The feedback is combined (30) with command signals (28) used to generate the high-frequency ac carrier signal, and the combination of the command signals with the negative sequence feedback is provided to an inverter (18) for generation of the high-frequency ac carrier signal, wherein the negative sequence feedback reduces unbalances in the resulting high-frequency ac carrier signal such that a balanced high-frequency carrier signal is provided to the motor/load.