Sensorless Rotor Flux Vector Positioning via Frequency Injection
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Solution Overview
Problem
Existing sensorless control methods for electric motors, particularly at low speeds, face inaccuracies in estimating the position of the rotor flux vector due to errors in motor model parameters, leading to poor motor control performance and the need for precise detection methods without relying on position sensors.
Innovation Solution
A method involving the injection of current vectors at specific frequencies into a rotating reference frame to determine the induced stator flux voltages, allowing for precise estimation of the rotor flux vector position by minimizing the error between actual and estimated positions, applicable to both synchronous and asynchronous motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If sensorless control based on main frequency voltage is used, then control simplicity is maintained, but measurement precision deteriorates at low speeds
Solution Approach 1:
The patent applies periodic action by injecting an auxiliary current at a specific frequency (different from the main frequency) into the stator windings. This periodic injection creates detectable voltage oscillations that allow the determination of rotor flux position even at low speeds, resolving the contradiction between control simplicity and measurement precision.
2Measurement precision
If low frequency current injection is used, then measurement precision improves at low speed, but device complexity increases
Solution Approach 1:
The patent changes the frequency parameter by injecting current at a specific frequency different from the main frequency. This parameter change enables the generation of detectable voltage oscillations that reveal rotor flux position information, improving measurement precision while maintaining a relatively simple control structure.
Solution Approach 2:
The patent introduces an intermediary approach by using voltage oscillations as a mediator to indirectly determine the rotor flux position. Instead of directly measuring position, the method uses the intermediary voltage oscillations generated by frequency-specific current injection to infer position information, balancing precision and complexity.
3Measurement precision
If position sensor is used, then measurement precision is ensured, but cost and reliability worsen
Solution Approach 1:
The patent replaces the mechanical position sensor system with an electrical field-based method. By injecting current at a specific frequency and analyzing the resulting voltage oscillations, the system determines rotor flux position without mechanical sensors, thereby improving reliability while maintaining measurement precision.
Solution Approach 2:
The patent uses voltage oscillations as an intermediary to indirectly determine position information, eliminating the need for direct mechanical position sensing. This intermediary approach maintains measurement precision while removing the reliability issues associated with physical sensors.
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
This approach provides a simple, precise, and reliable method for determining the rotor flux vector position, even at zero speed, without the need for position sensors, enhancing motor control accuracy and stability across various speed conditions.
Implementation Method 1
the injection of a first current vector into a first injection frame rotating at a first frequency with respect to a reference frame synchronous with the rotation of the motor... determining a first induced stator flux voltage
Data Source
Figure 1
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AI summary
The method involves injecting two current vectors respectively into injection reference frames rotating at two frequencies relative to a reference frame synchronous with the rotation of an electric motor. Stator flux induced voltages respectively delivered at outputs of two integrator modules (12, 13) synchronous with the frames are determined. Position of a rotor flux vector is regulated by minimizing an error (epsilon) between a real position of the flux vector and an estimated position of the flux vector, where the error is determined based on one of the voltages.