Salient Pole Offset PMSM Flux-Weakening Across Full Speed Range
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Solution Overview
Problem
The flux-weakening control method developed for traditional permanent magnet synchronous motors is not effective for salient pole offset permanent magnet synchronous motors due to their unique mathematical model and topology, which affects voltage limit ellipses, maximum torque per ampere control, and maximum torque per voltage control.
Innovation Solution
A flux-weakening control method and system specifically designed for salient pole offset permanent magnet synchronous motors, which involves determining electromagnetic torque, calculating current trajectories in dq and d′q′ coordinate systems, and using PI controllers to adjust direct and quadrature axis currents, thereby enabling effective flux-weakening control across a full speed range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional flux-weakening control method is applied to salient pole offset permanent magnet synchronous motor, then the control system can be simplified, but the control effect deteriorates due to different mathematical model and topology
Solution Approach 1:
The patent transforms the control problem by changing the coordinate system parameters. It rotates the dq coordinate system by a specific angle to obtain a new d′q′ coordinate system, where the voltage limit ellipse becomes aligned with the coordinate axes. This parameter transformation allows the application of simplified flux-weakening control methods while maintaining effectiveness for the salient pole offset motor topology.
2Speed
If direct axis flux-weakening current is injected to broaden speed range, then the speed range is improved, but the torque output deteriorates due to mismatch with the motor's special mathematical model
Solution Approach 1:
The patent introduces a new dimensional perspective by rotating the coordinate system. Instead of directly controlling flux-weakening in the original dq frame, it transforms the control to the d′q′ frame where the voltage ellipse is aligned, allowing simultaneous optimization of both speed range and torque output through proper current trajectory control in the transformed coordinate system.
Data Source
AI summary
The provided is flux-weakening control method and system for the salient pole offset permanent magnet synchronous motor. The method includes determining the given value of electromagnetic torque according to the actual speed and the given target speed; calculating the current trajectories of MTPA and MTPV in dq coordinate system; obtaining the d′q′ coordinate system by rotating the coordinate system, and calculating the current trajectory of MTPA and MTPV in the d′q′ coordinate system to obtain the characteristic current; judging whether it is necessary to turn on the flux-weakening control, and outputting the direct axis current compensation when it turns on; judging the flux-weakening area of the motor; and generating the space vector pulse width modulation signal to drive the motor to realize the full speed range flux-weakening speed regulation of the salient pole offset permanent magnet synchronous motor.