Multi-Winding Induction Motor Control Using Slip Angle Synchronization
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Solution Overview
Problem
Existing power converter systems for multiple winding induction machines face challenges in synchronizing field orientations between separate power converter devices, particularly due to the changing slip angle under load conditions, which requires high-bandwidth communication links that are often not readily available or practical.
Innovation Solution
The method involves determining a first slip angle estimate in a master power converter based on estimated rotor flux and mechanical angle, and transmitting this estimate to follower power converters, where a slip angle reference is determined to align field orientations, reducing the need for high-bandwidth communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If field orientation is sent directly from master to follower converter devices, then field orientation synchronization is achieved, but high bandwidth communication link is required which increases system complexity and cost
Solution Approach 1:
The patent uses slip angle as an intermediary parameter to achieve field orientation synchronization. Instead of directly transmitting the complex field orientation data from master to follower converters, the system transmits only the slip angle estimate, which is then used by follower converters to calculate their respective field orientations. This intermediary approach significantly reduces communication bandwidth requirements while maintaining synchronization accuracy.
Solution Approach 2:
The patent extracts only the essential information (slip angle estimate) needed for synchronization from the complete field orientation data. By transmitting only this critical parameter rather than the entire field orientation state, the communication burden is reduced while still enabling accurate synchronization at the follower converters.
2Speed
If high bandwidth communication link is implemented between converter devices, then fast field orientation transmission is achieved, but CPU load and bandwidth available for other signals is reduced
Solution Approach 1:
The patent extracts and transmits only the minimal necessary data (slip angle estimate) required for synchronization, rather than transmitting complete field orientation information. This extraction approach achieves fast synchronization response while preserving substantial communication bandwidth for other control signals and system communications.
Solution Approach 2:
The patent changes the parameter being transmitted from complex field orientation data to a simpler slip angle estimate. This parameter transformation reduces the data transmission requirements while maintaining the ability to achieve synchronization, thereby preserving CPU resources and communication bandwidth for other system functions.
3Loss of information
If mechanical position of rotor is used for field orientation, then position information is available, but synchronization fails due to changing slip angle under load
Solution Approach 1:
The patent implements a feedback mechanism where the master converter continuously estimates the slip angle based on actual operating conditions (currents, voltages, speed) and transmits this estimate to follower converters. This feedback approach ensures that field orientation remains accurate under varying load conditions, as the slip angle estimate adapts to real-time operational state rather than relying on fixed mechanical position data.
Data Source
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AI summary
A method for controlling a power converter system and a power converter system comprising a first power converter (10) connected to a first stator winding of an induction motor (30) having a rotor, the first stator winding and a second stator winding, and a second power converter (20) connected to the second stator winding of the induction motor (30), the first power converter (10) being configured to transmit a slip angle estimate to the second power converter (20), and the second power converter (20) being configured to determine a slip angle reference on the basis of the slip angle estimate transmitted from the first power converter (10) and a predetermined phase shift between the second stator winding and the first stator winding and to determine a rotor flux angle estimate on the basis of the determined slip angle reference and a mechanical angle of the rotor.