Sensorless Synchronous Machine Positioning Under Magnetic Saturation
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Solution Overview
Problem
Existing sensorless control methods for synchronous machines face challenges in accurately determining rotor position across the entire speed range, especially under load conditions, due to issues with current-dependent parameterization of inductance and anisotropy shift, which often require complex measurements or additional sensors.
Innovation Solution
A method for determining load-dependent position assignment parameters of a synchronous machine without a position sensor, using pulsed terminal voltages to calculate inductance and admittance, and compensating for magnetic saturation and anisotropy, allowing for accurate rotor position estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless control methods are used to avoid position sensors, then device complexity and cost are reduced, but measurement precision of rotor position deteriorates under load conditions
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the injection frequency based on operating conditions. The method adapts the excitation frequency to match the electrical frequency of the synchronous machine, which varies with rotor speed. This allows accurate inductance measurement across different operating points without requiring additional sensors, thereby maintaining measurement precision while avoiding sensor complexity.
Solution Approach 2:
The patent uses an intermediary approach by introducing high-frequency voltage injections to indirectly measure rotor position through inductance variations. Instead of directly measuring position, the method injects test signals and analyzes the resulting current responses to infer position information. This intermediary measurement technique enables sensorless control while maintaining accuracy under load conditions.
2Measurement precision
If current-dependent parameterization of inductance is used to improve accuracy under load, then measurement precision improves, but device complexity and measurement requirements increase
Solution Approach 1:
The patent implements self-service by having the control system automatically identify and store current-dependent inductance parameters during operation. The system performs self-calibration by injecting test signals at different current levels and automatically building the inductance-current relationship curves. This eliminates the need for external test equipment or complex manual parameterization, achieving high measurement precision while keeping the system self-contained.
Solution Approach 2:
The patent applies preliminary action by pre-characterizing the inductance-current relationship before normal operation. During an initialization phase, the system measures inductance at various current levels and stores these characteristics for later use. This preliminary measurement enables accurate real-time position estimation without requiring complex real-time calculations, reducing both device complexity and computational burden during operation.
3Adaptability or versatility
If online identification methods are used to track inductance changes, then adaptability to load changes improves, but response time deteriorates due to processing delay
Solution Approach 1:
The patent uses periodic action by implementing discrete identification steps at predefined operating points rather than continuous real-time tracking. The system identifies inductance parameters at specific current levels and uses these pre-determined values during operation. This periodic identification approach provides good adaptability to load changes while avoiding the time delays associated with continuous online calculation, as the system simply looks up pre-characterized parameters based on current measurements.
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
Enables accurate rotor position estimation in synchronous machines across various operating conditions, improving the efficiency and reliability of sensorless control without the need for additional sensors.
Implementation Method 1
The synchronous machine is excited by pulsed terminal voltages u(t) and the resulting current i(t) is evaluated. From this, the inductance L and the admittance Y are calculated.
Implementation Method 2
compensating for magnetic saturation and anisotropy, allowing for accurate rotor position estimation
Implementation Method 3
evaluate the position dependence of the machine's inductance
Data Source
Figure 1
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AI summary
The invention relates to a method or a device for load-free determining of load-dependent positioning parameters of a synchronous machine without a position sensor, which is controlled via pulsed terminal voltages from which, and in combination with the measured current response, the inductance or admittance is calculated or wherein from the load-free lowest and the load-free highest differential inductance are known, wherein based on the load-free lowest and the load-free highest differential inductance and the short-circuit current, the magnetic saturation behaviour under the load of the absolute inductance and/or the magnetic anisotropy of the synchronous machine is predicted and used in the position-sensor-free control operation for positioning.