Sensorless Motor Control via Magnetic Saturation Voltage
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Solution Overview
Problem
Existing power conversion devices for synchronous motors face challenges in accurately estimating the magnetic pole position at zero speed and low speed ranges due to the influence of current on Induced Voltage by Magnetic Saturation (IVMS), leading to difficulties in achieving desired driving characteristics.
Innovation Solution
A power conversion device that includes a motor control unit capable of estimating the magnetic pole position using detected current and IVMS, switching between different energization modes to adjust voltage application and torque generation, considering both the intensity and direction of the current to maintain accurate position estimation and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensor-less control using induced voltage is used to eliminate position sensors, then device complexity is reduced, but measurement precision deteriorates around zero speed and low speed ranges
Solution Approach 1:
The patent changes the operating parameters by applying specific voltage patterns (120-degree energization) and measuring induced voltage under controlled conditions. By varying the energization pattern and measuring the induced voltage response, the system can estimate magnetic pole position even at zero speed where conventional induced voltage methods fail.
Solution Approach 2:
The patent introduces induced voltage by magnetic saturation (IVMS) as an intermediary measurement signal. Instead of directly measuring position or relying on conventional induced voltage, the system uses IVMS generated under specific energization conditions as a mediator to infer magnetic pole position information.
2Ease of operation
If IVMS-based control is used to improve low speed performance, then driving characteristics are improved, but measurement precision deteriorates when current effects are not considered
Solution Approach 1:
The patent implements feedback by detecting the actual current flowing through the motor and using this information to correct the magnetic pole position estimation. The current detection result is fed back into the estimation process to compensate for current-induced errors in IVMS measurement, thereby maintaining precision across different operating conditions.
Solution Approach 2:
The patent adjusts the estimation approach based on current parameters. By detecting current magnitude and direction, the system dynamically modifies how IVMS is interpreted to account for current effects, ensuring accurate position estimation regardless of current conditions.
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 device achieves desired driving characteristics around zero speed and in low speed ranges by accurately accounting for current effects on IVMS, enabling precise control and torque generation without relying on position sensors.
Implementation Method 1
a method which detects induced voltage (speed electromotive voltage) generated by rotation of the synchronous motor and estimates a magnetic pole position based on induced voltage information
Implementation Method 2
a method which estimates a magnetic pole position by detecting induced voltage caused by magnetic saturation (hereinafter called "IVMS") based on 120-degree energization of a synchronous motor
Data Source
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Figure 3(a)~3(b)
Figure 4(a)~4(b)
AI summary
The purpose of the present invention is to provide a power conversion device capable of obtaining driving characteristics desired around zero speed and in a low speed region regardless of how much induced voltage caused by magnetic saturation is affected by current. The power conversion device converts an AC voltage or a DC voltage to an arbitrary AC voltage to control a three-phase AC synchronous electric motor and is characterized by being provided with a control unit for controlling the three-phase AC synchronous electric motor in six energizing modes by selecting two phases to be energized from among the three phase windings of the three-phase AC synchronous electric motor, wherein said control unit estimates the magnetic pole position of the three-phase AC synchronous electric motor on the basis of the detected voltage of a non-energized phase of the three phase windings and the detected current of an energized phase of the three phase windings and controls the three-phase AC synchronous electric motor using the estimated magnetic pole position.