Sensorless Rotor Angle Detection in Synchronous Machines
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Solution Overview
Problem
Existing methods for determining the rotor angle of synchronous machines, especially at standstill, are either reliant on sensors or suffer from reduced accuracy and reliability, and are prone to undesired torque formation and noise generation.
Innovation Solution
A sensorless method involving the generation of test voltage pulses in a predefinable sequence to determine the rotor angle based on current responses, using characteristic curves for salient and non-salient-pole machines, which minimizes the number of pulses required and enhances accuracy, while reducing dependence on current sensors and avoiding significant torque buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensors are implemented to detect rotor angle, then measurement precision is improved, but device complexity and manufacturing costs increase
Solution Approach 1:
The patent replaces mechanical/sensor-based rotor angle detection with a sensorless method using electrical test pulses and current response analysis. The control device injects voltage pulses into the stator windings and analyzes the resulting current responses to determine rotor angle, eliminating the need for physical sensors while maintaining measurement capability through electrical field interactions.
Solution Approach 2:
The synchronous machine itself provides the measurement information through its own electrical characteristics. By analyzing the current response of the machine's windings to injected test pulses, the system uses the machine's inherent electrical properties (inductance, resistance, magnetic characteristics) to determine rotor angle without external sensing components.
2Device complexity
If iterative test pulses are used for sensorless rotor angle determination, then device complexity is reduced, but measurement precision and reliability deteriorate
Solution Approach 1:
The patent systematically varies multiple parameters of the test pulses including amplitude, duration, frequency, and injection sequence to optimize the current response characteristics. By changing these electrical parameters and analyzing their effects on current magnitude and phase, the method achieves accurate rotor angle determination through multi-parameter analysis rather than relying on a single test pulse approach.
Solution Approach 2:
The patent extends the analysis from single-dimensional current magnitude measurement to multi-dimensional analysis including current magnitude, phase angle, rate of change, and temporal characteristics. This multi-dimensional parameter space provides redundant information that improves measurement precision and reliability while maintaining sensorless operation.
3Measurement precision
If multiple voltage pulses are generated for accurate rotor angle determination, then measurement precision is improved, but loss of energy and heat generation increase
Solution Approach 1:
The patent employs periodic injection of test pulses at specific intervals during the motor control cycle, utilizing idle periods or transitions when the motor is not under full load. This periodic action allows multiple measurements to be taken over time to improve precision while distributing the energy loss across multiple low-power events rather than continuous high-power operation.
Solution Approach 2:
The patent applies test pulses with amplitudes and durations optimized for measurement precision rather than full power operation. By using partial action (reduced amplitude pulses) sufficient for detection purposes, the system achieves adequate measurement precision without the excessive energy loss that would result from using full-power pulses.
4Measurement precision
If test pulses are applied for rotor angle determination, then measurement capability is improved, but object-generated harmful factors (torque formation and noise) increase
Solution Approach 1:
The patent compensates for the torque effects generated by test pulses by applying counteracting control actions. The control device detects the torque ripple or unwanted mechanical effects caused by pulse injection and applies compensating current adjustments to cancel these harmful effects, preventing them from affecting motor operation or generating noise.
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 improves the robustness and reliability of rotor angle determination, reduces manufacturing costs, and allows for self-diagnosis without external calibration, minimizing noise and heat development, and effectively reduces the risk of undesired torque formation.
Implementation Method 1
In order to provide a required torque with a synchronous machine, a rotating electric field is generated in the stator of the machine and rotates synchronously with the rotor
Implementation Method 2
feeding at least one initial voltage pulse of predefinable pulse length and pulse height into the stator of the synchronous machine, detecting the respective current response to the at least one initial voltage pulse, determining the respective phase difference on the basis of the respective detected current response
Data Source
AI summary
A method and a device for establishing the rotor angle of a synchronous machine. In one embodiment, the method includes the steps of feeding at least one initial voltage pulse of predefinable pulse length and pulse height into the stator of the synchronous machine, detecting the respective current response to the at least one initial voltage pulse, determining the respective phase difference on the basis of the respective detected current response, establishing at least one first estimated value by comparing the current response with a current response characteristic curve of the synchronous machine, establishing at least one second estimated value by comparing the phase difference with a phase difference characteristic curve of the synchronous machine, forming a multiplicity of differences between each of the first estimated values and each of the second estimated values, and determining an initial estimated value for the rotor angle of the synchronous machine on the basis of the determined difference having the lowest value.