Sensorless Rotor Position Detection in Synchronous Machines
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Solution Overview
Problem
Existing methods for determining the rotor position of field-oriented synchronous machines are limited in accuracy and control efficiency, particularly in sensorless operations, leading to reduced bandwidth and increased dead time in current control loops.
Innovation Solution
The method involves detecting motor current and setting motor voltage using pulse width modulation, superimposing a signal synchronous with the modulation frequency, and determining an estimated rotor angle position by separating current components, which is then used to improve control behavior by reducing error angles and feeding the remaining current component to a current controller, allowing for extrapolation of future current values for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensorless position detection is carried out by superimposing a high-frequency signal on the pulse-width-modulated output voltage and separating the high-frequency component, then rotor position can be determined without sensors, but the control bandwidth is reduced and dead time increases
Solution Approach 1:
The patent replaces the conventional mechanical/electrical separation approach with a mathematical signal processing approach. By using parameterized fitting functions to directly calculate and subtract the fundamental wave component from measured current values, the high-frequency component can be extracted without the bandwidth limitations and dead time associated with physical filtering methods.
Solution Approach 2:
The patent changes the parameters of the current signal representation by using parameterized functions (polynomials for fundamental wave, triangular functions for high-frequency components) to model the current values. This parameter-based approach allows for precise separation of signal components and enables real-time position determination without the performance degradation seen in conventional methods.
2Ease of operation
If conventional current control loops are used with fundamental wave component separation, then current control can be maintained, but dead time increases and control precision decreases
Solution Approach 1:
The patent performs preliminary action by pre-defining parameterized fitting functions that accurately represent both the fundamental wave component and the high-frequency injection signal. These functions are prepared in advance with known parameters, allowing for rapid calculation and separation of current components without introducing additional dead time into the control loop.
Solution Approach 2:
The patent creates mathematical copies of the current signal components using parameterized functions. By fitting polynomials to represent the fundamental wave and triangular functions to represent the high-frequency components, the system can separate and process each component independently and simultaneously, eliminating the sequential processing delays inherent in conventional approaches.
Data Source
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AI summary
Method for determining the rotor position of a synchronous machine with field-oriented control which has an effective inductance which is dependent on the rotor position, wherein the motor current is detected and the motor voltage is set using a pulse width modulation method, wherein a signal which is synchronous to the pulse width modulation frequency is superimposed on the motor voltage value to be set, wherein values for the motor current are detected in synchronism with the pulse width modulation frequency, wherein a current component brought about by the superimposed voltage signal and a residual current component, i.e. the fundamental component, are determined, wherein an estimated rotor angle position is determined from the current component brought about by the superimposed voltage signal, the phase angle of said rotor angle position being reduced with respect to the actual rotor angle position by means of a flux model, wherein the residual current component is supplied to a current regulator.