Inverter Control Device for Sensorless Motor Polarity Detection
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Solution Overview
Problem
Existing rotary sensorless control methods for magnet-type synchronous motors face challenges in accurately determining the magnetic pole position, especially at high speeds and with small magnet magnetic flux, leading to reduced accuracy and potential noise generation.
Innovation Solution
An inverter control device that includes a current command generator, current detector, gate command generator, rotary phase angle estimator, and polarity determination part, which uses magnetic flux and voltage signals synchronous with the rotor frequency to estimate the rotary phase angle and correct it for accurate polarity determination, enhancing the accuracy of rotary sensorless control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a harmonic current method is used to detect magnetic pole position, then the control can be simplified, but the accuracy of magnetic pole position determination is lowered at high speeds
Solution Approach 1:
The patent changes the detection parameter from harmonic current to magnet induced voltage. By using the voltage signal generated by the rotating magnet, the system achieves accurate magnetic pole position detection at high speeds where harmonic current detection fails, while maintaining relatively simple control architecture.
2Measurement precision
If a harmonic voltage is applied to determine magnetic pole position, then the position can be detected, but noise is generated
Solution Approach 1:
The system uses the magnet induced voltage that is naturally generated by the rotating magnet itself, rather than applying an external harmonic voltage. This self-generated voltage signal provides the necessary position information without introducing additional noise into the system.
3Device complexity
If a magnet induced voltage method is used, then the control structure is simplified, but the accuracy is insufficient for motors with small magnet magnetic flux at high speeds
Solution Approach 1:
The patent introduces a polarity determination part as an intermediary component that processes the magnet induced voltage signal. This component determines the polarity of the voltage signal to identify the magnetic pole position, enabling accurate detection even when the induced voltage amplitude is small, thus resolving the limitation for motors with small magnet magnetic flux.
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 solution improves the accuracy of rotary sensorless control for magnet-type synchronous motors, ensuring precise magnetic pole position determination even at high speeds and reducing noise, thereby enhancing the reliability of the motor control system.
Implementation Method 1
even with respect to an electric motor of a method which uses a magnet induced voltage, in the case of an electric motor having a small magnet magnetic flux
Data Source
AI summary
A device according to an embodiment including a command generator that generates a current command value; a detector that detects a current value to be outputted from an inverter to an motor; a generator that generates a gate command to the inverter, and obtains an output voltage target vector of the inverter based on the gate command; an estimator that obtains a rotary phase angle estimated value of the motor based on the detected current value and the output voltage target vector; and a polarity determination part that, with supply of a current in synchronism with a rotor frequency of the motor, performs determination of a magnet magnetic pole using a generated magnetic flux or voltage in synchronism with the generated rotor frequency or both of them, and outputs a correction value for the rotary phase angle estimated value based on a result of the determination.