Wind Turbine Rotor Position Determination Using Feedback Loop
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Solution Overview
Problem
Current methods for determining the rotor position of a synchronous electrical generator in wind turbines face challenges such as inaccurate zero crossing detection due to noise, lengthy calibration times, and the need for real-time encoder health tracking to prevent failures.
Innovation Solution
A method involving determining a voltage of the electrical generator, estimating a rotor position angle based on this voltage, and using a feedback loop with a phase locked loop and PI controller to adjust the rotor position estimate, while also calibrating the encoder offset and monitoring for encoder malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If zero crossing detection is used for encoder offset calibration, then the method is simple to implement, but the detection accuracy is poor due to noise
Solution Approach 1:
The patent introduces an intermediary signal processing chain between the raw voltage signal and the zero crossing detection. This includes coordinate transformation to convert three-phase voltages to two-phase voltages, followed by low-pass filtering to remove high-frequency noise, and then zero crossing detection. The intermediary filtering step acts as a mediator that preserves the essential zero crossing information while eliminating noise that would otherwise degrade detection accuracy.
Solution Approach 2:
The patent replaces direct mechanical/electrical zero crossing detection with a signal processing-based approach. Instead of directly detecting zero crossings from noisy voltage signals, the system substitutes a computational method involving coordinate transformation and digital filtering. This substitution allows for more robust and accurate detection by processing the signal in the digital domain where noise can be effectively filtered.
2Device complexity
If only one zero crossing point per cycle is used for calibration, then the method is computationally simple, but the calibration time is long
Solution Approach 1:
The patent implements continuous rotor position estimation by processing multiple zero crossing points throughout the calibration process rather than relying on a single measurement. The system continuously filters voltage signals and detects zero crossings at multiple instances, accumulating data to improve the accuracy of offset calculation. This continuous action reduces calibration time by parallelizing the information gathering process across multiple cycles and zero crossing events.
Solution Approach 2:
The patent uses excessive action by detecting and processing multiple zero crossing points beyond the minimum single point required for calibration. By utilizing several zero crossing events from multiple voltage phases and multiple cycles, the system gathers more data than strictly necessary, which improves the statistical accuracy of the offset calculation and reduces the overall calibration time through redundant measurements.
3Measurement precision
If encoder offset calibration is performed before power supply, then the phase angle alignment is achieved, but the process time is extended
Solution Approach 1:
The patent performs preliminary filtering and signal preparation actions before the actual zero crossing detection and offset calculation. By pre-processing the voltage signals through coordinate transformation and applying low-pass filters in advance, the system prepares clean, ready-to-analyze signals that speed up the subsequent calibration steps. This preliminary action ensures that when calibration begins, the data is already optimized for rapid and accurate processing.
Solution Approach 2:
The patent employs periodic action by utilizing the periodic nature of the three-phase voltage signals to its advantage. The system performs coordinate transformation and zero crossing detection at regular intervals corresponding to the electrical cycles of the generator. By synchronizing the calibration process with the periodic voltage waveforms and using multiple periodic cycles for measurement, the system achieves accurate phase angle alignment efficiently without requiring excessive time.
Data Source
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AI summary
A method for determining a rotor position of an electrical generator in a wind turbine is described comprising determining a voltage of the electrical generator, determining a rotor position angle estimate based on the voltage of the electrical generator, determining a subsequent rotor position angle estimate through a feedback loop, based on a combination of the voltage of the electrical generator and the rotor position angle estimate. Further, a method to real time track encoder health is described comprising determining the phase angle of a reference voltage, determining the angle difference between the rotor position and the reference voltage, and determining the differentiation of the angle difference.