Torque Control for Synchronous Machines via Flux Estimation
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Solution Overview
Problem
Synchronous electric motors with permanent magnets in motor vehicles face challenges in precisely controlling torque due to variations in magnetic flux caused by temperature changes, leading to inefficiencies and inaccuracies in torque production.
Innovation Solution
A method to control the torque of a synchronous electric machine by estimating the magnetic flux based on operating conditions, including temperature, and using this estimate to generate stator current setpoints that adjust the excitation voltage, ensuring precise and efficient torque production across varying speeds and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the magnetic flux is assumed constant for torque control, then the control system is simple, but torque precision deteriorates due to temperature variations
Solution Approach 1:
The patent implements a feedback mechanism where the magnetic flux is continuously estimated based on measured stator currents and voltages, and this estimated flux is fed back to adjust the torque control. The flux estimator monitors the actual magnetic flux variations due to temperature and uses this information to correct the torque command, thereby maintaining torque precision without requiring complex temperature sensing and compensation systems.
2Measurement precision
If the magnetic flux is estimated using thermal models, then torque precision is maintained, but the system complexity increases
Solution Approach 1:
The patent replaces complex thermal modeling and temperature measurement systems with an electrical-based flux estimation approach. By using measured stator currents and voltages along with machine parameters to estimate the magnetic flux, the system avoids the need for temperature sensors, thermal models, and associated compensation mechanisms, thereby maintaining torque precision while minimizing system complexity.
3Measurement precision
If high currents are applied to maintain torque at low flux, then torque precision is maintained, but energy efficiency deteriorates
Solution Approach 1:
The patent implements dynamic adjustment of the magnetic flux estimate based on real-time operating conditions. The flux estimator continuously updates the flux value according to the actual stator currents and voltages, allowing the control system to adapt the current commands optimally. This dynamic approach ensures that currents are neither excessively high nor low, maintaining torque precision while optimizing energy efficiency across varying operating conditions.
4Use of energy by moving object
If the operating point is optimized for a fixed flux value, then efficiency is maximized, but adaptability to temperature changes deteriorates
Solution Approach 1:
The patent dynamically changes the magnetic flux parameter based on operating conditions by estimating it from measured stator currents and voltages. This estimated flux value is used to continuously update the optimal operating point, allowing the system to adapt to temperature variations and other changing conditions. The control system recalculates the optimal currents based on the updated flux estimate, thereby maintaining both efficiency and adaptability.
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 allows for precise torque control with improved efficiency, compensating for temperature variations and manufacturing dispersions, and extends the lifespan of magnets by preventing demagnetization, thereby maintaining performance and reliability.
Implementation Method 1
the currents in the three phases of the stator are sinusoidal and each phase-shifted by 2π/3 rad. These currents create a rotating magnetic field in the electrical machine. Like a compass, the rotor naturally aligns itself with the rotating magnetic field created by the stator.
Implementation Method 2
It is the amplitudes of the stator currents and the power of the rotor magnets that create the torque necessary for the rotation of the machine.
Implementation Method 3
a thermal model of the rotor is used to deliver a temperature value of the rotor
Data Source
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AI summary
The invention relates to a method according to which stator current set points are generated on the basis of an estimation of a selectively determined rotor magnetic flux, according to the operating conditions of the machine, depending on the operating temperature of the rotor of the machine and further depending on the measured values of the current (Id, Iq) and the excitation voltage (Vq) of the rotor and the speed of rotation of the rotating magnetic field (ωr) generated by the rotor, the stator current set points being generated on the basis of the estimated magnetic flux.