Motor Control Device Voltage Vector Correction for Flux Estimation
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Solution Overview
Problem
The single shunt current detecting method for motor control systems faces challenges in accurately estimating magnetic flux linkage, leading to estimation errors and requiring complex voltage correction processes, especially when applied to direct torque control and vector control methods.
Innovation Solution
A motor control device that includes a motor current detector, a specified voltage vector generator, a corrector for the voltage vector, and a magnetic flux estimator, which corrects the specified voltage vector to suppress estimation errors by converting it into a three-phase voltage format, allowing for direct torque control and vector control without the need for three-phase voltage detectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single current sensor is used to detect bus current for phase current detection, then cost is reduced, but measurement precision of magnetic flux linkage deteriorates due to estimation errors
Solution Approach 1:
The patent applies parameter changes by modifying the voltage vector parameters (amplitude and phase) to compensate for estimation errors in magnetic flux linkage. The correction unit adjusts the voltage vector based on the detected phase current and estimated magnetic flux linkage, thereby improving measurement precision while maintaining the single sensor configuration
Solution Approach 2:
The patent implements feedback by using the detected phase current and estimated magnetic flux linkage to continuously correct the voltage vector parameters. The correction unit provides feedback adjustment to compensate for estimation errors, ensuring accurate motor control despite using only one current sensor
2Reliability
If voltage correction is applied to separate maximum and intermediate phase voltages, then current detection reliability is improved, but device complexity increases due to complex correction processes
Solution Approach 1:
The patent simplifies the voltage correction process by changing parameters in the voltage vector domain rather than individually correcting each phase voltage. The correction unit adjusts the voltage vector parameters (amplitude and phase) based on detected current and estimated flux, which inherently separates the correction for maximum and intermediate phases without requiring complex conditional logic for each phase
3Measurement precision
If specified voltage values are corrected to prevent voltage level convergence, then current detection accuracy is improved, but productivity decreases due to additional correction calculations
Solution Approach 1:
The patent improves calculation efficiency by changing to voltage vector parameters (amplitude and phase) instead of correcting each phase voltage individually. The correction unit computes adjustments in the vector domain, which reduces the number of calculations required while maintaining current detection accuracy
Solution Approach 2:
The patent replaces the mechanical approach of individual phase voltage correction with a mathematical transformation in the voltage vector domain. By using coordinate transformation and vector parameter adjustment, the system achieves the same correction effect with fewer computational steps, improving productivity
Data Source
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AI summary
A motor control device includes a motor current detector for detecting motor current flowing in a three-phase motor based on current flowing between an inverter driving the motor and a DC power supply, a specified voltage vector generating portion for generating a specified voltage vector indicating a voltage vector to which an applied voltage to the motor should follow based on a magnetic flux linkage of an armature winding of the motor, a specified voltage vector correcting portion for correcting the generated specified voltage vector, and a magnetic flux estimating portion for estimating the magnetic flux linkage based on the motor current and the specified voltage vector after the correction. The motor control device controls the motor via the inverter in accordance with the specified voltage vector after the correction.