Predictive Controller for Rotating Electrical Machine Switching Losses
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Solution Overview
Problem
Direct torque control (DTC) methods for rotating electrical machines face significant switching losses due to semiconductor switching, which increase operational costs and reduce system reliability, limiting their application in high-power scenarios.
Innovation Solution
The method involves generating and evaluating switching sequences for a rotating electrical machine to minimize switching losses by calculating optimal switching states and sequences using a predictive model, allowing for reduced switching frequency and improved torque control within predefined limits, thereby reducing switching losses and total harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct torque control (DTC) is used to control torque and electromagnetic flux in rotating electrical machines, then control performance and reliability are improved, but switching losses increase significantly
Solution Approach 1:
The patent applies model predictive direct torque control (MPDTC) which uses a mathematical model to predict future switching sequences and their effects on torque, stator flux, and neutral point potential. By calculating optimal switching sequences in advance based on predicted trajectories, the controller can minimize switching losses while maintaining reliable torque control within hysteresis limits.
Solution Approach 2:
The patent changes the control parameters by introducing a quality criterion that maps switching losses and switching frequency, allowing the controller to optimize switching sequences based on minimum switching losses rather than traditional hysteresis control alone. This parameter change enables significant reduction in switching losses while maintaining control performance.
2Measurement precision
If switching frequency is increased to improve torque control precision, then control precision is improved, but switching losses increase
Solution Approach 1:
The patent introduces a quality criterion that explicitly maps switching losses and switching frequency, allowing the controller to find the optimal balance between control precision and switching losses. By evaluating multiple candidate switching sequences with different switching frequencies and selecting the one with minimum quality value (minimum switching losses), the system achieves precise torque control within hysteresis limits without excessive switching frequency.
Solution Approach 2:
The controller uses a mathematical model to predict the trajectories of torque, stator flux, and neutral point potential for multiple candidate switching sequences in advance. This preliminary calculation allows selection of the optimal switching sequence that achieves desired control precision while minimizing switching losses, rather than relying on high switching frequency alone.
3Loss of energy
If model predictive direct torque control (MPDTC) is implemented to reduce switching losses, then switching losses are reduced, but computational complexity increases
Solution Approach 1:
The patent segments the control process into distinct steps: generating candidate switching sequences, calculating their trajectories using the mathematical model, evaluating them with the quality criterion, and selecting the optimal sequence. This segmentation of the control algorithm into manageable stages reduces computational complexity by organizing calculations systematically and allowing for efficient implementation of MPDTC.
Data Source
AI summary
To minimize switching losses in a rotating electrical machine, exemplary embodiments of the present disclosure proposes an iterative control method which calculates optimal switching states in advance. A rotating electrical machine can be controlled on the basis of this iterative control method.