Sensorless Rotating Machine Control for Low-Pulsation Rotor Estimation
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Solution Overview
Problem
Conventional position sensor-less control methods for rotating machines result in torque and power pulsations due to estimation errors in rotor position, which can adversely affect mechanical and power systems.
Innovation Solution
A control device for rotating machines that includes a voltage application unit, current detector, control unit, pulse-width modulator, and position estimator, which applies rectangular stator voltages, detects stator currents, and uses a filter to estimate rotor position, reducing estimation errors through synchronization with the fundamental frequency of the rotating machine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency signals are applied to estimate rotor position, then rotor position estimation accuracy is improved, but torque pulsation and noise increase
Solution Approach 1:
The patent extracts and removes the harmful high-frequency components from the estimated rotor position signal while preserving the useful low-frequency position information. This is achieved by passing the estimated position through a low-pass filter that separates the desired position signal from the harmful high-frequency pulsations, thereby maintaining measurement precision while eliminating torque pulsation and noise.
Solution Approach 2:
The patent converts the harmful high-frequency signals into useful information by using them to identify and remove specific frequency components. The high-frequency signals that cause torque pulsation are deliberately applied, then their frequency characteristics are used to design a filter that removes exactly those frequency components from the position estimate, transforming the harmful effect into a beneficial filtering criterion.
2Device complexity
If conventional observer methods are used to estimate rotor position, then device complexity is reduced, but estimation accuracy deteriorates due to voltage and current errors
Solution Approach 1:
The patent implements a feedback mechanism where the estimated rotor position is continuously refined by comparing the actual motor behavior with the model predictions. The position estimate is fed back through the filtering process, and the filtered position is used to improve subsequent position estimates, progressively reducing the impact of voltage and current measurement errors while maintaining a relatively simple observer structure.
3Speed
If simple filtering is applied to rotor position estimate, then processing speed is improved, but estimation accuracy deteriorates
Solution Approach 1:
The patent employs a dynamic filtering approach where the filter characteristics are adapted based on the operating conditions of the motor. The filtering parameters are adjusted dynamically to match the fundamental frequency of the motor, allowing the system to maintain high processing speed while preserving accuracy across different operating speeds. This dynamic adaptation enables the filter to track the fundamental frequency without introducing significant phase lag or amplitude attenuation.
Data Source
AI summary
A control device includes a current detector that detects a stator current flowing between a voltage application unit and a stator winding of a rotating machine; a control unit that computes a voltage command value that is a command value for a stator voltage to be applied to the stator winding on the basis of the stator current and a rotor position serving as position information of a rotor of the rotating machine; a PWM modulator that performs on-off control of switching elements of the voltage application unit so that a smoothed value of the stator voltage matches the voltage command value; and a position estimator that estimates, on the basis of the voltage command value and the stator current, the rotor position through a filter that removes a frequency component of a fundamental frequency of rotational speed of the rotating machine.