PMSM Current Control Using Deadbeat Prediction at High Speed
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Solution Overview
Problem
Existing control methods for permanent magnet synchronous electric machines (PMSMs) face challenges in achieving high performance, particularly at high speeds and low switching-to-fundamental ratios, due to parameter uncertainties, converter nonlinearity, and back emf harmonics, leading to inefficiencies and torque ripple.
Innovation Solution
A Deadbeat Predictive Current Control (DBPCC) scheme is implemented, which determines d-axis and q-axis current correction values independently of machine parameters and power electronics, using adaptive gain values and harmonic correction components to improve control accuracy and robustness, and estimates the inductance of the PMSM to enhance control performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional Field Oriented Control (FOC) is used for PMSM drives, then the control is simple to implement, but the performance deteriorates significantly at high machine speeds due to low switching-to-fundamental ratio
Solution Approach 1:
The patent transitions from conventional FOC to Deadbeat Predictive Current Control (DBPCC), fundamentally changing the control strategy parameters. DBPCC uses predictive algorithms that calculate optimal voltage vectors based on current errors and machine parameters, enabling high-performance control at high speeds where conventional FOC fails due to low switching-to-fundamental ratio
2Speed
If Direct Torque Control (DTC) or Model Predictive Control (MPC) is used to replace FOC, then transient performance improves, but the control complexity increases
Solution Approach 1:
The patent extracts and eliminates the complex flux and torque observers that are typically required in DTC and MPC schemes. By using DBPCC with direct current error feedback and predictive voltage selection, the system achieves fast transient response without the need for complex observation algorithms, thereby reducing overall control complexity while maintaining high transient performance
3Measurement precision
If high order back emf estimator is used to improve MPCC performance, then steady-state performance improves, but the dynamic response becomes slower and it fails to account for inverter non-linearity
Solution Approach 1:
Instead of using complex high-order estimators that filter out high-frequency components (slowing dynamic response), the patent inverts the approach by using simple current error feedback combined with deadbeat predictive control. This directly addresses the current deviation caused by inverter non-linearity and parameter variations, achieving both fast dynamic response and accurate steady-state performance through the predictive nature of DBPCC
4Measurement precision
If disturbance observer based DBPCC is used, then steady state error compensation is achieved, but computational complexity increases and high frequency disturbances occur due to converter nonlinearity
Solution Approach 1:
The patent employs a self-service mechanism where the DBPCC algorithm inherently compensates for steady-state errors through its predictive nature and direct current error feedback. By calculating the optimal voltage vector based on predicted current behavior and actual current measurement, the system automatically corrects deviations without requiring separate disturbance observers, thereby reducing computational complexity while maintaining steady-state accuracy
5Measurement precision
If online parameter identification is used to compensate for parameter uncertainty, then control accuracy improves, but chattering occurs and fine-tuning of observer parameters is required
Solution Approach 1:
The patent performs preliminary identification of machine parameters (inductance, resistance, flux linkage) during the commissioning phase and stores them for use in the DBPCC algorithm. This preliminary action eliminates the need for continuous online parameter identification and observer tuning during operation, avoiding chattering and simplifying implementation while maintaining high control accuracy through the robust predictive control law
Data Source
AI summary
A method of controlling a permanent magnet synchronous electric machine (PMSM) drive using a Deadbeat Predictive Current Control (DBPCC) scheme is provided. The method comprises: determining d-axis and q-axis stator current values (id, iq) representative of a measured PMSM current; determining d-axis and q-axis reference current values (id*, iq*); based on the stator current values (id, iq) and the reference current values (id*, iq*), determining d-axis and q-axis current correction values (Cd, Cq); determining corrected reference current values (id**, iq**) as a sum of the reference current values (id*, iq*) and the current correction values (Cd, Cq); and controlling the PMSM drive using the corrected reference current values (id**, iq**) as reference current inputs of the DBPCC scheme. A controller for performing the method; a system comprising the controller, a PMSM and associated power electronics; and a computer program for performing the method are also provided.