Torque ripple reduction method in position sensorless control at standstill/low-speed operation of the wound-field synchronous motor with double three-phase wound stator

This paper presents the reduction method of torque ripple in position sensorless control at standstill/low-speed region of the wound-field synchronous motor with double three-phase wound stator for Integrated Starter Generator(ISG). High-frequency signal injection method which is commonly used for PMSMs is selected for the test motor's position sensorless control. Due to the injected signal, a large torque ripple is generated on the output torque. As our target machine, Wound-field Synchronous Motor with Double Three-phase Wound Stator, has two sets of three-phase windings, we proposed a method by injecting signal to the set of windings in the opposite sign to reduce the torque ripple. The proposed method can realize position sensorless control but also reduce the torque ripple significantly. The effectiveness of the proposed sensorless control method is shown by actual experiment.

I. Introduction

In recent years, because global warming and natural resource depletion have become serious issues, electric vehicles and hybrid vehicles are quickly developing. However, from the perspective of cost, ICE (Internal Combustion Engine) vehicles are still widely used thus improvement of ICE vehicle's fuel efficiency becomes an extremely important issue as well. Therefore, a method of using an alternator mounted in the ICE vehicle as a motor is attracting attention. If an alternator is used as a motor to start and assist engine (micro/mild hybrid technology), improvement in cost-effectiveness of fuel consumption can be realized. This kind of alternator is called Integrated Starter Generator(ISG) [1].