PMSM Predictive Current Control for Harmonic Torque Ripple
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Solution Overview
Problem
Permanent-magnet synchronous machines experience torque ripples due to harmonic torque caused by dead time and non-linear inverter characteristics, leading to increased iron and copper losses, current overshoot, and safety hazards, which complicates control and limits their application scope.
Innovation Solution
A control method using a model predictive control algorithm to predict d-axis and q-axis currents, subtracting harmonic components, and determining control policies based on cost functions to simplify the system structure and suppress harmonic currents without the need for PI controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of PI controllers are used to suppress harmonic current, then the harmonic current suppression effect is improved, but the control system complexity increases
Solution Approach 1:
The patent combines multiple PI controllers into a single model predictive control algorithm. Instead of using separate PI controllers for each harmonic component (5th and 7th order), the invention integrates harmonic suppression functionality into the MPC cost function, allowing simultaneous control of fundamental and harmonic currents through one unified control structure.
Solution Approach 2:
The model predictive control algorithm performs multiple functions simultaneously: it controls the fundamental current components for normal motor operation while also suppressing harmonic current components. The cost function is designed to evaluate and minimize both fundamental and harmonic current errors, making the controller universal for multiple control objectives without requiring separate dedicated controllers.
2Reliability
If a large number of PI controllers are used to suppress harmonic current, then the harmonic current suppression effect is improved, but the parameter adjustment complexity increases
Solution Approach 1:
The patent merges multiple parameter adjustment tasks into a single set of PI parameters for the model predictive controller. Instead of adjusting PI parameters for each individual harmonic suppressor, the invention uses one unified cost function with consolidated parameters that simultaneously optimize fundamental and harmonic current control, dramatically reducing the number of parameters that need tuning.
Solution Approach 2:
The invention changes the parameter structure from multiple PI controller parameters to a unified model predictive control parameter set. The cost function uses a single proportional gain and integral gain that work together to suppress harmonics while controlling fundamental currents, transforming the parameter adjustment task from complex multi-parameter tuning to simpler unified parameter optimization.
3Object-generated harmful factors
If harmonic current components are extracted and suppressed using traditional methods, then the torque ripple is reduced, but the control system complexity increases
Solution Approach 1:
The patent extracts only the essential harmonic current components (5th and 7th order) that cause torque ripple, rather than attempting to suppress all harmonics. By identifying and targeting specifically the dominant harmonic orders responsible for torque ripple, the invention achieves effective torque ripple reduction while maintaining a relatively simple control structure through the unified MPC approach.
Data Source
AI summary
This application provides a permanent-magnet synchronous machine control method and device, and a permanent-magnet synchronous machine control system. The method includes: obtaining a d-axis current id and a q-axis current iq in a permanent-magnet synchronous machine control loop at a current moment; obtaining a fifth-order harmonic current id5th and a seventh-order harmonic current id7th in the d-axis current id in the permanent-magnet synchronous machine control loop at the current moment, and a fifth-order harmonic current iq5th and a seventh-order harmonic current iq7th in the q-axis current iq in the permanent-magnet synchronous machine loop at the current moment; determining a d-axis current idk+1 at a next moment in each switch state; determining a q-axis current iqk+1 at the next moment in each switch state based on the first current idk, the second current iqk, and the second voltage in each switch state; and determining a control policy of the permanent-magnet synchronous machine.