Three-Phase Motor Rotor Position Detection Using Neutral Point Potentials
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Solution Overview
Problem
Existing control methods for three-phase synchronous motors, particularly in electric power steering devices, face challenges in accurately detecting rotor position when driven by multiple inverters, leading to reduced position detection accuracy and increased noise at low speeds.
Innovation Solution
A control device that estimates rotor position using neutral point potentials from both three-phase windings connected to different inverters, allowing for independent control of each inverter and reducing magnetic interference, thereby enhancing position detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple inverters are used to drive one three-phase synchronous motor, then system reliability and power output are improved, but magnetic interference between systems increases and position detection accuracy deteriorates
Solution Approach 1:
The patent segments the inverter operation into distinct time slots, with each inverter operating independently during its assigned period. The control device alternates between first and second inverters, allowing position detection during periods when the other inverter is inactive, thereby eliminating magnetic interference while maintaining system reliability through redundant inverter capacity.
Solution Approach 2:
The control device implements periodic alternation between two inverters, switching them on and off in a timed sequence. During each period, one inverter is activated for motor drive while the other remains inactive for position detection, creating a rhythmic pattern that eliminates continuous magnetic interference and enables accurate sensorless control.
2Measurement precision
If neutral point potential detection is used for position estimation, then position detection capability is improved, but interference from other inverter systems increases
Solution Approach 1:
The patent extracts the position detection function from the active inverter period and performs it during the inactive period of the other inverter. By separating the detection operation from the simultaneous operation of multiple inverters, the method eliminates magnetic interference that would otherwise corrupt the neutral point potential measurements, enabling accurate position estimation.
3Measurement precision
If rotor position is detected using induced voltage at low speeds, then position information can be obtained, but sensitivity decreases and noise increases
Solution Approach 1:
The control device performs position detection during the inactive period of the other inverter, before the interfering inverter is activated. This preliminary detection during a quiet electrical environment captures clean position information without the noise and reduced sensitivity that would result from simultaneous inverter operation, enabling accurate low-speed control.
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 improves rotor position detection accuracy by suppressing interference from other systems, enabling precise motor control even at low speeds and reducing noise, thus enhancing the reliability of electric power steering systems.
Implementation Method 1
a position detection unit that detects a neutral point potential of the three-phase winding
Implementation Method 2
a method of directly detecting the induced voltage (speed electromotive voltage) generated by the rotation of the rotor provided with a magnet
Data Source
AI summary
Provides are a control device for a three-phase synchronous motor in which a position detection accuracy of a rotor can be improved when one three-phase synchronous motor is driven by a plurality of inverters, and an electric power steering device using the same. A control device for a three-phase synchronous motor includes: a three-phase synchronous motor including a first three-phase winding and a second three-phase winding; a first inverter connected to the first three-phase winding; a second inverter connected to the second three-phase winding; a first control device that controls the first inverter on the basis of a rotor position of the three-phase synchronous motor; and a second control device that controls the second inverter on the basis of the rotor position of the three-phase synchronous motor. The first control device estimates the rotor position on a basis of a neutral point potential of the first three-phase winding and a neutral point potential of the second three-phase winding.