Sensorless Rotary Machine Control with High-Frequency Position Estimation
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Solution Overview
Problem
Existing position-sensorless control methods for rotary machines with structurally small saliency ratios face challenges in maintaining accurate rotor position detection due to non-elliptical high-frequency current vector loci, leading to decreased detection accuracy.
Innovation Solution
A rotary machine control device that includes a current detection unit, position estimation unit, current control unit, and position-estimating voltage generation unit, which generates high-frequency voltages superimposed on driving voltages to enhance rotor position estimation by controlling magnetic saturation, using a coefficient value to adjust high-frequency voltage amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-frequency voltage is superimposed on the drive voltage to estimate rotor position using saliency, then rotor position detection is enabled in low-speed region, but detection accuracy decreases when saliency ratio is structurally small
Solution Approach 1:
The patent changes the operating parameters by superimposing a high-frequency voltage component on the drive voltage. This high-frequency voltage has an amplitude that varies depending on the saliency ratio, allowing the system to adapt to rotary machines with small saliency ratios. The position estimation unit processes the current response to this high-frequency voltage to extract rotor position information, maintaining detection accuracy across different machine types.
Solution Approach 2:
The patent implements dynamic adjustment of the high-frequency voltage amplitude based on the detected saliency ratio. The position estimation unit dynamically processes the current vector locus to extract position information even when the saliency ratio is small. This dynamic adaptation allows the system to maintain effective position estimation across varying machine characteristics and operating conditions.
2Ease of manufacture
If position-sensorless control is implemented to reduce manufacturing cost and size, then manufacturing cost and size are reduced, but rotor position detection accuracy decreases in low-speed region
Solution Approach 1:
The patent replaces the mechanical position sensor with an electronic position estimation system. The position estimation unit uses mathematical processing of the current vectors to estimate rotor position without physical sensors. By superimposing high-frequency voltage and analyzing the current response, the system achieves position detection accuracy comparable to sensor-based methods while maintaining the cost and size benefits of sensorless control.
3Device complexity
If high-frequency voltage with fixed amplitude is applied for position estimation, then position estimation is simplified, but detection accuracy decreases when saliency ratio is small
Solution Approach 1:
The patent implements dynamic adjustment of the high-frequency voltage amplitude based on the detected saliency ratio. The position estimation unit dynamically processes the current vector locus to extract position information even when the saliency ratio is small. This dynamic adaptation allows the system to maintain effective position estimation across varying machine characteristics and operating conditions.
Solution Approach 2:
The system uses feedback from the current detection unit to monitor the response to high-frequency voltage. The position estimation unit analyzes this feedback information to estimate the saliency ratio and adjust the high-frequency voltage amplitude accordingly. This closed-loop approach maintains detection accuracy while adapting to different rotary machine characteristics.
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 effectively reduces the decrease in detection accuracy of rotor position even in rotary machines with structurally small saliency ratios by stabilizing the current vector loci into an elliptical shape, ensuring accurate rotor position estimation.
Implementation Method 1
The position-estimating voltage generation unit generates a high-frequency voltage having a frequency higher than the first voltage command, the high-frequency voltage being a position-estimating voltage for estimating the rotor position, on the basis of a physical quantity correlated with magnetic saturation of the rotor
Data Source
AI summary
A control device includes: a current detection unit that detects a rotary machine current flowing through a rotary machine; a position estimation unit that calculates an estimated value of a rotor position of a rotor on the basis of the rotary machine current; a current control unit that generates a first voltage command for driving the rotary machine on the basis of a detected rotary machine current and an estimated rotor position; a position-estimating voltage generation unit that generates a high-frequency voltage having a frequency higher than the first voltage command, and being a voltage for estimating the rotor position, on the basis of a torque-axis current command correlated with magnetic saturation of the rotor; and a voltage applier that applies a driving voltage to the rotary machine on the basis of a second voltage command in which the position-estimating voltage is superimposed on the first voltage command.