Sensorless Rotor Angle Detection via Voltage Subtraction in Three-Phase Inverters
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Solution Overview
Problem
Existing methods for mechanical sensorless control of three-phase machines require complex measurement technologies and mechanical encoders or high-quality machine models, which increase costs and reduce robustness, and often necessitate additional hardware and signal processing.
Innovation Solution
A method where the rotor position is determined by subtracting voltage equations during different converter switch positions, with only one phase being currentless, allowing for the calculation of rotor or flux angle using terminal voltage measurements and optional current measurements, eliminating the need for a star point connection and simplifying signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical encoder is used for rotor position measurement, then high-quality flux determination is achieved, but device complexity and cost increase while robustness decreases
Solution Approach 1:
The patent replaces the mechanical encoder with an electrical measurement system that uses voltage and current measurements combined with signal processing algorithms to determine rotor position and flux angle, thereby eliminating mechanical components while maintaining measurement precision
Solution Approach 2:
The patent introduces intermediate electrical measurements (voltage and current) as mediators to indirectly determine rotor position and flux angle without direct mechanical sensing, using these electrical quantities as proxies to achieve the desired measurement precision
2Measurement precision
If a high-quality machine model is used for flux determination, then measurement precision is improved, but device complexity and signal processing requirements increase
Solution Approach 1:
The patent uses the machine's own electrical measurements (voltage and current) to determine its own state variables (flux angle and rotor position) through signal processing, making the system self-sufficient without requiring external mechanical sensors or complex pre-programmed machine models
3Ease of operation
If terminal voltage measurement with respect to any reference point is used, then ease of operation is improved, but measurement precision may be affected
Solution Approach 1:
The patent inverts the traditional approach by not requiring measurement with respect to the machine star point, instead using terminal voltages with respect to any reference point and compensating through signal processing, thereby simplifying the electrical connection requirements while maintaining sufficient measurement precision
4Device complexity
If two-phase power supply with one currentless phase is used during angle determination, then device complexity is reduced, but productivity may be affected
Solution Approach 1:
The patent employs periodic switching of converter phases to create the two-phase power supply condition with one currentless phase during specific measurement intervals, allowing rotor position determination without continuous three-phase operation, thereby simplifying the measurement structure while maintaining control quality through periodic execution
Data Source
Figure 1
AI summary
The method involves feeding current in two phases, when an inverter is operated in switching positions that are used for analyzing rotor position of a three-phase AC machine (5). Third phase is stopped, and information about a rotor angle and/or a flow angle is provided by using voltage equations obtained by subtracting two inverter switching positions that occur consecutively, where different inverter switching positions have a same dead phase. A sign change of sine of dual rotor angle and/or the flow angle is used as criteria for an indexing table of a current range index to produce torque. An independent claim is also included for a switching arrangement for executing a three-phase alternating current machine controlling method.