Rotor Position Estimation During Active Short Circuit
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Solution Overview
Problem
Existing methods fail to determine the position and rotational speed of a rotor in an electric machine during an active short circuit when rotor position sensors fail, leading to potential damage during emergency operation.
Innovation Solution
A method that determines the rotor position and speed by analyzing short-circuit currents, calculating stator and rotor current angles, and using a characteristic relationship to derive the rotor position and speed, even in the absence of sensors, with optional smoothing to reduce inaccuracies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an active short circuit is automatically activated above emergency operating speed to prevent damage, then the electric machine is protected from damage, but the electric machine cannot operate in emergency mode
Solution Approach 1:
The patent replaces sensor-based mechanical/electrical detection systems with a mathematical model-based detection system. By using a sensorless observer that processes current signals and machine parameters to estimate rotor position and speed, the system eliminates the need for physical sensors during emergency operation, enabling both protection and emergency mode capability.
Solution Approach 2:
The patent changes the operational parameters by switching from sensor-based measurement to model-based estimation. The observer dynamically adjusts its estimation based on machine parameters and measured currents, allowing the system to determine rotor state without relying on traditional sensor feedback, thus enabling emergency operation while maintaining protection.
2Measurement precision
If rotor position sensors are used to determine position and speed, then accurate measurement is achieved, but the system fails when sensors malfunction
Solution Approach 1:
The patent extracts the position and speed determination function from the physical sensors and relocates it to a mathematical observer. By separating the measurement function from the sensing hardware and implementing it through software-based estimation using current signals and machine models, the system eliminates sensor failure risks while maintaining measurement precision.
Solution Approach 2:
The patent introduces a sensorless observer as an intermediary that mediates between the available current measurements and the required position/speed information. This observer processes electrical signals and machine parameters to generate accurate rotor state estimates without direct sensor input, providing both precision and reliability.
3Adaptability or versatility
If the electric machine operates in emergency mode without sensor protection, then emergency operation is enabled, but the risk of machine damage increases
Solution Approach 1:
The patent implements preliminary action by pre-calculating and storing characteristic relationships between current magnitude and rotor current angle during normal operation. This pre-established data allows the sensorless observer to accurately estimate rotor position and speed during emergency operation, enabling safe operation while maintaining protection against damage through continuous monitoring.
Data Source
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AI summary
The invention relates to a method for determining the position (ӨR) and the rotational speed (nR) of a rotor of an electrical machine during an active short circuit and a rotor-state determining device (10) designed to carry out the method. The method comprises the steps of determining the short circuit currents (Iu, Iv, Iw) resulting during the short circuit, determining a total current (Iα, Iß) resulting from the short circuit currents (Iu, Iv, Iw), determining a stator current angle (ψι) of the total current (Iα, Iß) with respect to a stator coordinate system (α, ß), determining a rotor current angle (φι) of the total current (Iα, Iß) with respect to a flux direction (dR) of the rotor, this step comprising the steps of calculating an amount variable (I) of the total current (Iα, Iß), determining the rotor current angle (φι) on the basis of a characteristic dependence between the amount variable (I) and a rotor current angle (φι), which dependence is created for the electrical machine, the rotor position (ӨR) corresponding to a sum of the stator current angle (ψι) and the rotor current angle (φι), and the rotor rotational speed (nR) resulting from monitoring of the rotor position (ӨR).