Wound Field Synchronous Machine Rotor Tracking via Exciter Current Harmonics
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Solution Overview
Problem
Existing methods for estimating rotor position in wound field synchronous machines, such as carrier injection sensorless and current harmonic-based techniques, face limitations including increased current burden and applicability only to specific motor configurations, necessitating a more reliable position information approach.
Innovation Solution
A method that estimates the initial rotor position using a carrier injection sensorless stimulation signal and tracks the operating position based on current harmonics of the polyphase exciter field, with calibration to ensure accurate positional control, employing an estimator and tracker module within an electromechanical power transfer system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If carrier injection sensorless method is used to estimate rotor position, then position information can be obtained, but increased current burden is placed on motor components
Solution Approach 1:
The patent uses current harmonics from the exciter field as an intermediary to indirectly estimate rotor position, rather than directly injecting carrier signals into the main motor windings. The exciter current harmonics serve as a mediator that carries position information without imposing heavy current burden on the main motor components.
Solution Approach 2:
The patent separates the position estimation function into a distinct exciter field system, independent from the main motor drive system. By using the exciter winding as a separate measurement channel, the main motor components are relieved from carrying additional measurement currents.
2Object-affected harmful factors
If current harmonic-based technique from exciter is used, then current burden is reduced, but the technique is only useful for motors with certain numbers of poles and configurations
Solution Approach 1:
The patent develops a universal position estimation method that works across different motor configurations by using exciter field current harmonics combined with a calibration process. The system can adapt to various pole numbers and configurations through the calibration of tracking parameters, making the method universally applicable rather than configuration-specific.
Solution Approach 2:
The patent employs parameter calibration and adjustment to adapt the position estimation algorithm to different motor configurations. By calibrating the tracking parameters based on the specific motor's exciter field characteristics, the system maintains accuracy across various pole numbers and configurations without requiring fundamental changes to the method.
3Measurement precision
If carrier voltage signal is superimposed on fundamental control signal, then rotor position can be estimated, but the technique requires complex signal processing and calibration
Solution Approach 1:
The patent extracts position information from the exciter field current harmonics separately from the main control signals, rather than superimposing carrier signals on the fundamental control signal. This extraction approach simplifies the signal processing by using an independent measurement channel that does not interfere with the primary control system.
Solution Approach 2:
The patent performs initial calibration to establish the relationship between exciter current harmonics and rotor position before normal operation. This preliminary calibration creates a reference framework that simplifies subsequent position tracking, eliminating the need for continuous complex signal processing during motor operation.
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 provides reliable rotor position information, reducing current burden and expanding applicability across various motor configurations, enabling precise control and efficient operation of wound field synchronous machines.
Implementation Method 1
A controller generates a carrier voltage signal, which is a relatively high-frequency signal, that is superimposed on a fundamental control voltage signal
Implementation Method 2
tracking any one of a number of reference positions of the rotor based on current harmonics of the polyphase exciter field
Data Source
AI summary
An example method of initiating operation of a wound field synchronous machine in a motoring mode includes estimating an initial position of a rotor of a wound field synchronous machine using a carrier injection sensorless stimulation signal. The method tracks an operating position of the rotor based on current harmonics of the wound field synchronous machine. The method also calibrates the tracking using the initial position.