Rotor Position Sensing with Encoder-Hall Fusion at Low Speed
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining rotor position in electrical machines, particularly in direct-drive wind turbines, face challenges such as unreliable operation in fractional-slot concentrated winding machines, low dynamic performance, instability at high rotor speeds, and harmonic interference, which affect accurate position and torque control, especially at low or zero rotational speeds.
Innovation Solution
A method and arrangement using an incremental mechanical encoder combined with Hall effect sensors to determine rotor position, where Hall effect sensors provide initial angle and gear ratio correction, enabling accurate rotor position determination even at low speeds, by integrating encoder measurement data with Hall effect sensor data to enhance control accuracy and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HFI observer is used to provide initial angle and correct gear ratio, then rotor position can be determined, but the method may not work reliably for fractional-slot concentrated winding machines due to lowered saliency
Solution Approach 1:
The patent introduces an incremental encoder as an intermediary device that mechanically couples to the rotor through a rubber wheel. This encoder provides direct mechanical position feedback that works independently of the generator's electromagnetic characteristics, thereby solving the incompatibility of HFI observer with concentrated winding machines while maintaining the ability to determine rotor position accurately
Solution Approach 2:
The patent replaces the electromagnetic-based HFI observer with a mechanical encoder system that uses physical contact through a rubber wheel to track rotor position. This mechanical substitution eliminates the reliability issues associated with HFI in concentrated winding machines, as the mechanical measurement is independent of the generator's magnetic saliency
2Reliability
If HFI is used for position determination, then initial angle can be provided, but the dynamic performance is relatively low affecting control stiffness
Solution Approach 1:
The patent replaces the slow electromagnetic HFI method with a mechanical encoder system that provides immediate position feedback through direct mechanical coupling. This substitution dramatically improves the dynamic response and control stiffness, as the mechanical encoder can track position changes in real-time without the delays inherent in electromagnetic field-based methods
3Measurement precision
If incremental encoder with rubber wheel is used, then rotor position can be sensed, but the rubber wheel diameter may change with working conditions affecting accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the encoder continuously measures rotor position and this information is used to correct for rubber wheel diameter changes. The system monitors the relationship between encoder measurements and expected rotor position, detecting deviations caused by wheel diameter changes and applying corrections to maintain measurement accuracy
Solution Approach 2:
The system performs self-correction by using its own measurement data to detect and compensate for rubber wheel diameter changes. Through continuous monitoring and automatic adjustment, the system maintains accurate rotor position measurement without external intervention, effectively compensating for the physical changes in the rubber wheel
4Measurement precision
If closed-loop PI regulation is used for gear ratio correction, then accuracy can be improved, but the integral term causes issues at very low rotor speeds
Solution Approach 1:
The patent implements a dynamic control strategy that adapts the regulation method based on rotor speed conditions. At very low speeds where PI regulation becomes unstable, the system switches to or relies on the incremental encoder's direct mechanical measurement capability, which remains stable and accurate across all speed ranges including zero speed, thereby maintaining both accuracy and reliability
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
The method provides high-resolution rotor position measurement, improving control performance and stability across various rotor speeds, including zero and low speeds, and enhances compatibility with concentrated winding generators for applications like single blade mounting.
Implementation Method 1
receiving Hall effect sensor measurement data from at least one, in particular at least three, Hall effect sensors, in particular binary sensors, installed at the stator (at known positions), in order to sense magnetic field (and/or magnetic field change)
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
It is described a method of determining a rotor position indicating quantity (166, θ), in particular rotor electrical angle, of an electrical machine (100) having a stator (102) and a rotor (103), in particular permanent magnet synchronous generator, in particular of a wind turbine (160), the method comprising: receiving encoder measurement data (168) regarding rotor position from an incremental mechanical encoder (127) installed in order to sense rotor position; receiving Hall effect sensor measurement data (169) from at least one, in particular at least three, Hall effect sensor (120), in particular binary sensors, installed at the stator (102), in order to sense magnetic field change; determining the rotor position indicating quantity (166) based on the encoder measurement data (168) and the Hall effect sensor measurement data (169).