Simplified Predictive Torque Control for Surface-Mounted PMSM Based on Equivalent Transformation and Partition Method

Tao Liu,Yan Cai,Zhanfeng Song

doi:10.1109/access.2020.2975026

Abstract

Predictive torque control (PTC) is one of the most widely discussed strategies for high performance permanent magnet synchronous motor (PMSM) drive system because of its fast dynamic response and good stability. However, the complex prediction and optimization process requires a large amount of computation. Until now, few studies have carried out any systematic research on the simplification of the PTC. In this paper, a stepwise simplification method for the PTC strategy is proposed. Firstly, by using the equivalent transformation, the prediction process is simplified without affecting the control performance of the PTC. On this basis, the cost function is further simplified with additional presuppositions, and the optimization process is replaced by honeycomb-structured space partitioning for optimal voltage vector searching. Therefore, the computation burden caused by the multiple calculations in traditional PTC is greatly reduced. In addition, this paper provides the implementation details of the proposed control strategy. Moreover, the comparison between the traditional PTC and two simplified PTC is carried out in the evaluation of the transient performance, steady-state errors, control characteristics, computation burden, and compatibility with additional constraints. The experimental results prove the feasibility and effectiveness of the simplified algorithms, and this is beneficial to the future application of PTC strategy in the low-cost motor drive system. Moreover, the simplified PTC algorithm can achieve higher switching frequency, thereby improving the performance of torque and stator flux in the motor drive system with the application of new generation SiC power device.

Highlights

In the past few years, Finite control set model predictive control (FCS-MPC) has developed rapidly and attracted growing interest of the researchers across various fields such as grid-connected power converter, motor driver, and renewable energy
In this paper, by analyzing the characteristics of predictive torque control (PTC), the equivalent transformation based PTC (ET-PTC) based on equivalent transformation is proposed
Different from other simplified algorithms, the ET-PTC completely maintains the characteristics of traditional PTC with simpler control structure

Summary

INTRODUCTION

In the past few years, Finite control set model predictive control (FCS-MPC) has developed rapidly and attracted growing interest of the researchers across various fields such as grid-connected power converter, motor driver, and renewable energy. In [13], the number of candidate voltage vectors is reduced by introducing a direct torque control (DTC) switching table in the induction motor drive system; In [14], the complex weighting factor selection process in the cost function is simplified by using the TOPSIS algorithm. In other circuit topologies such as the four-switch three-phase inverter-fed PMSM drive system, or the matrix converter-fed PMSM drive system, the simplified method for PTC algorithm is realized by converting the capacitor voltage offset (CVO) control and torque control into flux linkage control, or by reducing the candidate voltage vectors needed in the prediction process [22], [23]. With the discussion concerning about the impact of the simplification process on the PTC strategy, the simplified algorithms are evaluated in terms of steady-state performance, transient performance, inherent decoupling characteristics, control object adjustment characteristic, and additional constraints compatibility on surface-mount PMSM experimental platform. Substituting (2) into (1), one can obtain the state equations about id and iq

Lq Lq

The electromagnetic torque T e can be calculated by

The electromagnetic torque Te can be expressed as

The sector number N can be identified by

Findings

CONCLUSION