新型宽弱磁调速范围的永磁同步电机及其控制方法研究

The excitation of permanent magnet synchonous motor can not be adjusted. The flux weakening control is nessesary when the speed is over base speed. The traditional flux weakening method is accomplished by applying a large minus d-axis demagnetizing current. Flux weakening obtained by this method reduce the efficency and constrain its applications. We present a rotor structue with Ld>Lq and control method which can adjust the airgap magnetic flux according to the operating mode of the motor.we build the magnetic circuit model, formulate the flux weakening principle,analyze the torque and flux weakening charactersitics and research on the design method of the motor with wide flux weakening speed range and control method. The scheme is verified the feasibility and validity for flux weakening by the method of analyis, finite element method simulation analysis and experiment research. The motor with Ld>Lq which increase the reluctance torque and permanent magnet torque and the torque below base speed is increased and the power density is higher. We control the current phase to realize flux weakening and the constant power operation speed range is widen with high efficency for without any minus large d-axis demagnetizing current. Meanwhile, the back electromotive force is lower in high speed which is easy less than direct busbar voltage when it occurs a accident and it is more reliable and safe.With the research and accomplishment of this project there will be a new large torque, wide speed range, high effeicency electrical driving system which takes better propect of amplications for electrical vehicle driving system,electrical spindle system and variable speed electric power generation.

永磁同步电机励磁不可调节，在基速以上运行时必须进行弱磁控制。传统方法通过增大负的直轴去磁电流实现弱磁控制，致使系统效率降低,限制了其应用范围。本课题提出了一种Ld>Lq的永磁转子结构方案和根据电机运行状态灵活调整气隙磁通的控制方法。建立电机的磁路模型,阐述弱磁机理,分析转矩和弱磁特性，研究宽弱磁调速范围电机的设计方法及控制策略。通过理论分析、有限元仿真和实验研究，验证该方案实现弱磁的有效性。该永磁电机的Ld＞Lq，不仅增加了磁阻转矩还增加了永磁转矩，从而增大低速输出转矩，提高功率密度；通过控制电枢绕组中电流相位而非增加负的弱磁电流实现弱磁，提高恒功率运行速度范围的同时又提高了电机效率，且高速反电势值低，故障时不易超过直流母线电压值，增加了可靠性和安全性。该项目的研究和完成，将形成一种新型大转矩、宽速域、高效率电驱动系统，在电动车辆驱动系统、电主轴系统以及变速发电等领域具有良好的应用前景。

永磁同步电机因励磁不可调节限制了电机的转速范围。本项目对永磁同步电机弱磁的相关问题进行了研究，主要获得以下几方面的研究进展。. （1）提出了一种Ld>Lq的新型宽弱磁调速范围的永磁同步电机及其控制方法。提供了一台调速比为1:3的永磁同步电机设计方案。为解决永磁同步电机弱磁困难提供了一条新途径。. （2）研究对比了两种转子结构的新型Ld>Lq的永磁同步电机。两种转子结构为具有磁桥的转子结构的和护套与转子磁轭分体式的转子结构。具有磁桥的转子结构的电机在弱磁特性和齿槽转矩脉动上优于护套与转子磁轭分体式转子结构的电机，在同等条件下后者能输出更大的电磁转矩和更高的效率。. （3）总结了宽弱磁调速范围的永磁同步电机的参数影响弱磁能力的变化规律。宽弱磁调速范围的永磁同步电机弱磁效果正比于气隙、电枢电流、偏心距离，护套中磁通调节段径向宽度和磁桥宽度，反比于极弧系数、匝数、永磁体厚度和永磁体到圆心的距离。. （4）总结了宽弱磁调速范围的永磁同步电机的设计方法的一般规律。第一，提升电机额定电磁转矩应增大极弧系数、匝数、额定电流和永磁体厚度，减小气隙长度、偏心距离、磁通调节段径向宽度和磁桥宽度。第二，具有宽弱磁调速范围的永磁同步电机齿槽转矩脉动可控制在0.5%以下。降低转矩脉动可以增大气隙、磁通调节段尺寸、磁桥宽度，减小偏心距离和永磁体到圆心距离。极弧系数和永磁体厚度存在最优值。第三，提升电机效率可以降低匝数和额定电流，减小磁通调节段宽度和磁桥宽度，增加永磁体到圆心的距离和偏心距离。第四，磁通调节段径向宽度和磁桥宽度设计是该电机设计的难点，设计时要平衡电磁转矩和弱磁能力。. 宽弱磁调速范围的永磁同步电机在电动车辆驱动系统等领域具有一定的应用前景。