Distributed VSD Control for Multi-Phase Electrical Machines
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Solution Overview
Problem
The VSD approach for controlling multi-phase electrical machines is limited by the need for a central controller and high-bandwidth communication links, and lacks fault tolerance when the main controller fails.
Innovation Solution
A method for controlling a 3n-phase electrical machine using n power converters, where each converter is controlled by a respective controller, estimating currents from other sets, and applying vector space decomposition (VSD) to minimize coupling effects and enable independent operation without a central controller, improving fault tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a central controller is used for VSD control of multi-phase machines, then comprehensive control of all phase currents is achieved, but the system complexity increases and fault tolerance decreases
Solution Approach 1:
The patent divides the control system into n independent controllers, each responsible for controlling one power converter and its associated three-phase winding set. Each controller performs VSD transformation locally using only its own measured currents, eliminating the need for a single central controller and thereby improving fault tolerance while reducing system complexity.
Solution Approach 2:
Each controller independently performs current measurement, VSD transformation, and control signal generation for its associated power converter without requiring information from or communication with other controllers. This self-contained operation enables the system to continue functioning even if one controller fails, significantly improving reliability.
2Loss of information
If a central controller with high-bandwidth communication is used, then all phase current information is available for control, but communication requirements and system complexity increase
Solution Approach 1:
The patent segments the current information processing so that each controller only needs to access and process its own locally measured three-phase currents. The VSD transformation is performed independently in each controller, eliminating the need for centralized collection and exchange of current information through high-bandwidth communication links.
Solution Approach 2:
The patent extracts the essential control function from the centralized architecture, allowing each distributed controller to perform the complete VSD control algorithm locally using only its own current measurements. This extraction eliminates the communication infrastructure requirement while maintaining full control capability.
3Manufacturing precision
If VSD transformation is performed centrally with all measured currents, then accurate current control is achieved, but the system cannot operate in master-follower configuration
Solution Approach 1:
The patent segments the VSD transformation operation so that each controller performs the transformation independently using only its own measured currents. This local transformation approach maintains current control accuracy while enabling flexible system configurations including master-follower arrangements, as each controller operates autonomously without requiring centralized coordination.
Data Source
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AI summary
A method of controlling a 3n-phase electrical machine (7) by means of n power converters (3a, 3b) each being controlled by a respective controller, and each power converter (3a, 3b) being configured to power a respective set of three phases of the electrical machine (7), wherein the method for each controller comprises: a) obtaining measured currents (ia,i, ib,i, ic,i, ia,2, ib,2, ic,2) of the set of three phases of the electrical machine (7) controlled by the controller, b) estimating all currents (îdq, 2, îdq, 1) of all the other sets of three phases of the electrical machine (7), which are controlled by the other controllers, c) transforming the measured currents (ia,1, ib,1, ic,1, ia,2, ib,2, ic,2) and all the estimated currents (îdq, 2, îdq, 1) using vector space decomposition, VSD, to obtain a set of VSD currents, and d) controlling the corresponding power converter based on the VSD currents.