Sensorless Rotary Machine Control with Synchronized Pole Estimation
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Solution Overview
Problem
Existing sensorless magnetic pole position estimation methods for rotary electric machines face challenges in reducing switching frequency and electromagnetic noise, while maintaining responsive position estimation, as they either suffer from low response frequency or increased switching losses and noise due to high-frequency voltage applications.
Innovation Solution
A controller that synchronizes the voltage command for estimation with the carrier wave, allowing for reduced switching frequency and noise by generating a voltage command on a stationary coordinate system fixed to the winding, extracting the frequency component from current detection values to directly estimate the rotational angle based on saliency-dependent inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency voltage is applied for magnetic pole position estimation using saliency, then position estimation accuracy is improved, but switching frequency increases causing increased switching losses and electromagnetic noise
Solution Approach 1:
The patent applies periodic high-frequency voltage to the stator winding at a frequency that matches the carrier wave frequency. This periodic action exploits the saliency of the rotor to generate position-dependent current responses, enabling magnetic pole position estimation without requiring additional sensors. The periodic nature of the voltage application allows for continuous position estimation while maintaining synchronization with the PWM carrier wave.
2Measurement precision
If high-frequency voltage is applied for magnetic pole position estimation, then position estimation is achieved, but electromagnetic noise increases
Solution Approach 1:
The patent converts the potentially harmful electromagnetic noise generated by high-frequency voltage application into a useful signal for position estimation. By carefully selecting the high-frequency voltage frequency to match the carrier wave frequency, the noise that would normally be problematic becomes a measurable response that carries position information. The current response to this high-frequency voltage is processed to extract magnetic pole position data, transforming what could be considered noise into beneficial measurement information.
3Object-affected harmful factors
If carrier wave frequency is increased to reduce audible noise, then noise outside human audible range is achieved, but switching losses increase
Solution Approach 1:
The patent changes the frequency parameter of the carrier wave to a value that is at or above the upper limit of the human audible range (20 kHz). This parameter change effectively eliminates audible electromagnetic noise from the system. The high-frequency voltage applied for position estimation is synchronized with this high-frequency carrier wave, allowing position estimation to be performed at frequencies that are imperceptible to humans while maintaining efficient switching operation.
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 reduces switching losses and electromagnetic noise while enhancing estimation response by maintaining a lower switching frequency, allowing for efficient and accurate magnetic pole position estimation without the need for additional sensors.
Implementation Method 1
The superimposing high frequency method which estimates the magnetic pole position of the rotor using the saliency of the rotary electric machine
Implementation Method 2
estimates the magnetic pole position from the amplitude change of the current resulting from the positional dependence of inductance
Implementation Method 3
a frequency component of the one period of the voltage command for estimation is extracted from the current detection value, and the rotational angle is estimated directly based on the frequency component
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
To provide a controller for rotary electric machine which can suppress the increase in the switching frequency by the voltage for estimation while reducing the estimation delay of the magnetic pole position (the rotational angle). A controller (10) for rotary electric machine turns on and off switching devices which the inverter (2) has and applies voltage to the winding, based on a comparison result between the voltage command and the carrier wave; generates the voltage command for estimation of a preliminarily set one period (Th) on a stationary coordinate system fixed to the winding; generates the carrier wave of the same one period (Th) as the one period (Th) of the voltage command for estimation; extracts the frequency component of the one period (Th) of the voltage command for estimation from the current detection value; and estimates a rotational angle (θ) based on the frequency component.