AC Motor Control via Phase Estimation and γ-δ Axis Separation
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Solution Overview
Problem
Conventional power conversion control devices for alternating current motors, especially those without position sensors, face challenges in achieving high-efficiency operation and robust control, particularly for motors like synchronous reluctance motors where the power factor is not easily controlled and motor characteristics vary significantly.
Innovation Solution
A control device for alternating current motors using a γ-δ axis control system, which includes a current distributor, current controller, voltage drop calculator, voltage commander, and phase estimator, allows for high-efficiency operation by controlling the γ-axis current to zero and applying voltages based on calculated phases to align with the δ-axis direction, thereby stabilizing the motor control despite varying characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional power conversion control devices use simple command operations without position and speed sensors, then device complexity is reduced, but control precision and reliability deteriorate for motors with varying characteristics
Solution Approach 1:
The patent introduces a feedback mechanism by calculating the actual phase angle from voltage and current measurements and comparing it with the command phase angle. This feedback loop enables the system to detect deviations and adjust control parameters accordingly, maintaining reliable control without adding position sensors.
Solution Approach 2:
The patent replaces mechanical position sensors with an electrical measurement-based phase detection system. By using voltage and current measurements to calculate phase angles, the system eliminates the need for mechanical sensing components while achieving equivalent or superior control precision.
2Ease of operation
If conventional control devices assume fixed motor characteristics, then control simplicity is maintained, but adaptability to motors with varying inductance values deteriorates
Solution Approach 1:
The patent implements dynamic adaptation by continuously calculating control parameters based on real-time voltage and current measurements. The phase angle calculation and current command generation adapt to changing motor characteristics such as inductance variations, enabling the system to maintain optimal performance across different operating conditions without complex manual configuration.
3Device complexity
If conventional control devices ignore voltage drops caused by wirewound resistance and inductance, then computational complexity is reduced, but measurement precision of phase angle deteriorates
Solution Approach 1:
The patent introduces an intermediary calculation step that computes voltage drops across resistance and inductance components before determining the final phase angle. This intermediary processing accounts for parasitic effects without requiring complex hardware, achieving high measurement precision through systematic computational correction.
4Loss of energy
If conventional control devices guide reactive component-axis voltage magnitude to zero, then high-efficiency operation is achieved for motors with power factor of 1, but productivity for motors with varying power factors deteriorates
Solution Approach 1:
The patent dynamically adjusts control parameters including current command values and phase angles based on real-time operating conditions and measured motor characteristics. This parameter adaptation enables the system to optimize efficiency for motors with power factor of 1 while simultaneously maintaining high productivity for motors with varying power factors, overcoming the limitation of fixed control strategies.
Data Source
AI summary
A control device for an alternating current motor according to embodiments includes a current distributor and a phase estimator. The current distributor divides a torque command by using a control phase and outputs a component that contributes to a mechanical output of the motor as a δ-axis current command and a component that does not contribute to the mechanical output as a γ-axis current command. The phase estimator computes a phase at which a γ-axis component of an addition amount of the output of the current controller and a voltage drop amount of inductance of the motor becomes zero and outputs the computed phase as the control phase.