Multilevel Design Optimization and Operation of a Brushless Double Mechanical Port Flux-Switching Permanent-Magnet Motor

This paper proposes a brushless double mechanical port flux-switching permanent-magnet motor for potential application in hybrid electric vehicles. To realize the design objectives of high-torque capability, low-torque ripple, and low-magnetic coupling between the inner and outer motors, a new multilevel design optimization method is proposed to conduct a multiobjectives optimization. First, by adopting the comprehensive sensitivity approach, the whole optimization design process is divided into three levels: nonsensitive level, mild-sensitive level, and strong-sensitive level. Then, to improve the whole design efficiency, the response surface method and multiobjective genetic algorithm are applied in the mild-sensitive level and strong-sensitive level, respectively. Based on the proposed design method, a compromise design among the three design objectives is considered and realized. Finally, a prototype motor is built to verify the validity of the proposed design method and motor operation.

I. Introduction

In recent years, double mechanical port permanent-magnet (DMP-PM) motors have attracted increasing attention and become one of the research highlights in the motor field [1], [2]. The four-quadrant energy transducer (4QT), which is one of the typical DMP-PM motors, has been the subject of research [3]. Compared with the single-port PM motor [4], the 4QT integrates two rotated mechanical ports and two electric ports into one compound motor frame. Thus, the mutual conversion and transformation between the mechanical and electrical energy can be obtained. And the function of power split and combination can be realized flexibly. Hence, the 4QT exhibits potential application prospect in many fields, such as modern hybrid electric vehicles (HEVs) and wind power generation systems [5], [6]. However, to realize the function of electric continuous variable transmission in such type of DMP-PM motors, the mechanical power from the engine is required to be equal to the sum of the transmitted power of the inner motor and the electrical power of the outer motor exactly, and then delivered to the drive line by the middle ports simultaneously [7]. Therefore, high control accuracy is required to meet such critical requirements of power balance. Moreover, since one set of windings is located in the inner rotational rotor, the slip rings and brushes are inevitably required to realize the input and output of the power flows, leading to the friction loss and regular maintenance.