Sensorless Rotor Position Estimation via Carrier Injection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional rotor position sensing systems for wound field synchronous machines at standstill are hindered by the need for additional components like resolvers, which are bulky, unreliable, and inefficient, especially in aeronautical applications where multiple machines must start a single engine, requiring a self-sensing or sensorless method to estimate rotor position accurately.
Innovation Solution
A carrier injection sensorless position sensing system is employed, utilizing a multiphase AC permanent magnet machine coupled to the wound field synchronous machine, where the stator is configured with a sub-multiple of poles, and multiphase AC power is applied to detect harmonic currents, converted to αβ coordinates, and rotated to estimate rotor position based on harmonic current vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resolver is mounted to the starter/generator rotor to provide rotor position information, then the required rotor position information is obtained, but the size, weight, complexity, and reliability are penalized
Solution Approach 1:
The invention extracts and eliminates the resolver component from the system by implementing a sensorless control method that estimates rotor position and speed through mathematical algorithms based on terminal voltage and current measurements, thereby obtaining the necessary position information without the physical resolver device
Solution Approach 2:
The invention replaces the mechanical resolver sensing system with an electronic sensorless estimation system that uses mathematical models and signal processing to determine rotor position and speed from electrical measurements, substituting mechanical components with computational methods
2Force
If multiple starter/generators are paralleled to provide full rated torque at standstill, then the required torque is achieved, but the system complexity and control difficulty increase
Solution Approach 1:
Each starter/generator in the parallel configuration is equipped with sensorless control that independently estimates its own rotor position and speed, allowing the system to self-regulate without complex inter-machine coordination, thereby reducing overall system complexity while maintaining full torque capability
3Device complexity
If carrier injection sensorless position sensing is used at standstill, then rotor position and velocity are accurately estimated without additional components, but the method requires sophisticated signal processing and control algorithms
Solution Approach 1:
The invention introduces an intermediary estimation process that uses terminal voltage and current measurements as intermediate variables to infer rotor position and speed, creating a bridge between easily measurable electrical quantities and the desired mechanical position information without requiring direct mechanical sensors
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 method allows for accurate estimation of rotor position and velocity without additional sensing components, enabling efficient operation of multiple starter/generators at standstill, overcoming the limitations of conventional systems by leveraging rotor saliencies and harmonic analysis.
Implementation Method 1
This technique works with any dynamoelectric machine that has rotor saliencies that result in a change in impedance as seen at the stator windings to the high frequency excitation signal.
Implementation Method 2
CIS works by applying a high frequency excitation signal with an electrical current or potential rotating waveform to the dynamoelectric machine at a high enough frequency that it sweeps around the stator faster than the rotor is turning
Implementation Method 3
At rotor standstill or low speed there is insufficient back electromotive force (EMF) generated in a dynamoelectric machine to enable an accurate estimate of rotor position using only passive measurement of terminal potentials and currents.
Data Source
AI summary
For a multiphase alternating current (AC) wound field synchronous machine (WFSM) that has a stator with a selected number of poles, the WFSM having an associated exciter and multiphase AC permanent magnet machine (PMM) directly coupled to the WFSM, a method of sensing the position of a rotor in the WFSM comprises the steps of: configuring a stator for the PMM to have a number of poles that is a sub-multiple of the selected number of WFSM stator poles; configuring a rotor for the PMM to have high saliency; applying multiphase AC power of a selected frequency to the PMM stator; detecting at least one set of stator harmonic currents of the multiphase AC power resulting from the rotor saliency; converting the detected PMM harmonic stator currents from their multiphase coordinates to αβ coordinates; rotating the converted PMM stator currents into a reference frame for at least one selected harmonic to generate αβ coordinate harmonic current vectors; and estimating the position of the WFSM rotor based on the values of the αβ coordinate harmonic current vectors in the selected harmonic reference frame.