Permanent Magnet Motor Control for Accurate Pole Position Correction
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Solution Overview
Problem
Existing control devices for permanent magnet type rotating electrical machines face inaccuracies in magnetic pole position correction due to errors in dead time correction, leading to deviations in the calculated magnetic pole position correction amount.
Innovation Solution
A control device that includes magnetic pole position detection means, an inverter for PWM control, middle point level judging means to compare potential levels, and magnetic pole position origin point correction amount operation means to calculate and apply a correction based on a two-phase signal, ensuring accurate magnetic pole position origin point correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic pole position correction is calculated from d-axis and q-axis voltage command values through dead time correction, then magnetic pole position correction can be performed, but accuracy deteriorates due to errors in dead time correction
Solution Approach 1:
The patent extracts the magnetic pole position correction calculation from the voltage command values that require dead time correction. Instead of calculating correction from Vd and Vq commands (which are affected by dead time errors), the system uses actual phase voltages after PWM conversion, thereby taking out the correction calculation from the problematic dead time correction chain and achieving accurate magnetic pole position correction without dead time error influence.
Solution Approach 2:
The patent introduces middle point voltages as an intermediary to obtain actual phase voltages. By detecting middle point potentials and calculating actual phase voltages from these middle point voltages, the system creates an intermediary measurement path that bypasses the dead time correction errors present in the voltage command values, thereby achieving accurate magnetic pole position correction.
2Ease of operation
If dq vector control is used for magnetic pole position correction, then correction can be performed during rotation, but accuracy deteriorates due to cumulative errors in voltage command conversion
Solution Approach 1:
The patent implements feedback by using actual phase voltages (obtained from middle point voltage detection) to calculate magnetic pole position correction. This feedback approach uses real measured values rather than theoretical command values, thereby eliminating cumulative errors from voltage command conversion and achieving high accuracy correction during rotation.
Data Source
AI summary
The control device of the alternative rotating electrical machine is configured as follows. a d-axis current command value and a q-axis current command value are kept at zero in dq vector control, in the state where the alternative rotating electrical machine is rotating. A time during which the output of the middle point level judging means is Hi is counted. A duty is calculated out from the ratio with a carrier wave cycle, and a conversion is conducted into a two-axis rotating coordinate system (three-phase to two-phase conversion) from the calculated out duty and the magnetic pole position, to calculate out a two-phase signal. The magnetic pole position origin point correction amount is calculated out based on a predetermined operation equation, from the two-phase signal. A magnetic pole position origin point correction is performed based on the calculated out magnetic pole position correction amount.