Three-Phase Motor Control With High-Frequency Flux Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensorless control methods for motor drives, particularly Direct Flux Vector Control (DFVC), face stability issues at low speeds due to inaccurate flux estimation, and rely on lookup tables (LUT) that are difficult to acquire and require significant memory and precision, especially under full load conditions without pre-equipped test loads.
Innovation Solution
A sensorless control method using a direct flux vector control module and a constant current angle locus module that determines torque references, flux references, and current references, injecting a high-frequency signal to estimate the motor's flux direction and norm, allowing for stable operation at low speeds without the need for lookup tables, and maintains stability by ensuring a fixed angle between the current and flux vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control methods are used to eliminate sensors and reduce cost, then device complexity and cost are reduced, but measurement precision of flux and position deteriorates
Solution Approach 1:
The patent applies high-frequency voltage injection to excite the motor and analyze the resulting current response. This vibration-based approach enables sensorless flux estimation by detecting the motor's electromagnetic response to high-frequency excitation, achieving precise flux measurement without physical sensors.
Solution Approach 2:
The patent replaces mechanical sensors (encoders, resolvers) with an electrical measurement system that injects high-frequency voltage signals and analyzes current responses. This substitution eliminates mechanical components while achieving equivalent or superior measurement precision through signal processing.
2Manufacturing precision
If lookup tables are used to store inductance data for MTPA operation, then manufacturing precision of control is improved, but device complexity and memory requirements increase
Solution Approach 1:
The patent enables the control system to self-identify motor parameters by injecting high-frequency voltage signals and analyzing the current response. The system automatically extracts inductance information and flux estimates without requiring pre-stored lookup tables, making the controller adaptive to different motor instances.
Solution Approach 2:
The patent changes the operating parameters by injecting high-frequency voltage signals at different amplitudes and frequencies to excite the motor under various conditions. This dynamic parameter variation enables real-time identification of motor characteristics without relying on static lookup tables.
3Ease of operation
If direct flux vector control is used for sensorless operation, then ease of operation is improved, but stability deteriorates at low speeds
Solution Approach 1:
The patent uses high-frequency voltage injection to create electromagnetic vibration that enables flux estimation at all speeds including standstill. This vibration-based measurement approach overcomes the low-speed instability problem of conventional sensorless DFVC by providing reliable flux information through the motor's high-frequency response.
Solution Approach 2:
The patent introduces high-frequency voltage injection as an intermediary mechanism to bridge the gap between stator voltage and rotor flux estimation. This intermediary signal provides additional information that stabilizes the flux estimator at low speeds where back-EMF-based methods fail.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed method provides stable torque production at low speeds and standstill, with smooth transitions to high speeds, reducing the risk of instability from rotor position estimation errors and minimizing current-induced losses, while operating efficiently near Maximum Torque Per Ampere (MTPA) conditions.
Implementation Method 1
injecting a high frequency signal on the reference voltage, determining from motor current vector an estimate of the direction of a flux of the motor
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The present invention concerns a device and a method for controlling a motor using a DFVC module and a CCAL module. The invention: - determines a torque reference, - determines, by the CCAL module, a flux reference and a current reference from the torque reference and a predetermined angle, - provides the flux reference and the current reference to the DFVC module in order to obtain a reference voltage to be provided to the motor, - injects a high frequency signal on the reference voltage, - determines, from motor current vector, an estimate of the direction of a flux of the motor, - determines, from the estimate of the direction of the flux, an estimate of a flux and an estimate of the current that flows perpendicular to the estimated direction of the flux, - provides the estimate of the flux and the estimate of the current that flows perpendicular to the estimated direction of the flux to the DFVC module.