Electromagnetism Design Of Permanent Magnet Motor For ISG Application And Research On Its Control System

In face of the increasingly serious problem of energy and environmental protection, developing vehicles which are fuel-efficient and environmentally friendly is imperative. As a part of new energy vehicles, hybrid electric cars are the most prosperous ones at this stage. The key technology of hybrid electric vehicles is the Integrated Starter-Generator system, in which Integrated Starter-Generator is an important part, so it is significant to stuy ISG technology.This thesis first compares strengths and weaknesses of several types of motors for ISG application, and then chooses the interior permanent magnet synchronous motor for ISG system application accroding to the relevant characteristics and performance requirements of hybrid cars. Then make an analysis of contradictions between low-speed startup and high-speed generation in ISG, based on the limitations of voltage and current、requirements for starting torque and generation in ISG system, the thesis gives a detailed analysis of the selection of basic design parameters, including flux linkage of permanent magnet、stator inductance、saliency ratio and pole pairs. These basic design parameters provide guidance for the detailed design of relevant geometry dimensions of motors by using magnetic circuit method and finite element software. Vehicle-based ISG also has its own specific characteristics such as high power density and it is affected by control strategy and operation condition. Considering these characteristics which are different from traditional motor design, it can conform more to actual situation by introducing control strategy in performance calculation. Besides, the equation between power and stator outside diameter is derived, so it is convenient to get the maximum power according to the space limitation of motor in vehicles. Unlike traditional design methods which only focus on performance of rated point, the method in this thesis focuses on analysing the calculation of overload capacity and field weakening range, which are relevant to quick start and overtaking capacity. Based on the magnetic circuit method, this paper use VC++ to write a motor electromagnetism design software, which can quickly and accurately calculate and check the parameters and performance of motors.Through electromagnetic simulation in JMAG software, several important parameters in magnetic circuit such as magnetic leakage factor、calculating polar arc factor, air gap flux waveform factor can be obtained so that it can make motor design more accurate. Besides, flux linkage of permanent magnet、d-q axis inductances can also be achieved. Then, this paper analyze the influence of cross-coupling of d-axis and q-axis magnetic circuit to stator inductance and electromagnetic torque. The results of electromagnetic transient simulation show that the motor designed can meet requirements of big starting torque and generation voltage and power.Finally, a simulation which adopting maximum torque/current and field weakening control strategy in starting mode and generation mode respectively is implemented, the results show that the ISG designed meets performance requirements.