永磁同步电动机转矩脉动抑制的控制策略研究

发布时间：2018-12-13 18:55

【摘要】：高效率,高性能,低成本是现代交流伺服系统的发展趋势。永磁同步电动机作为伺服系统中重要一环,具有结构简单、体积小、效率高、运行可靠、调速范围宽、动静态特性好等优点,广泛的用于工业生产、国防、日常等各个方面。但永磁同步电动机转矩脉动的存在使其在高精度场合的应用受到了限制,同时,转矩的脉动还导致了转速的脉动。所以研究永磁同步电动机的转矩脉动抑制策略,增加转矩平滑度,具有重大的工程意义。本文从控制的角度,对引起电磁转矩脉动的纹波转矩和齿槽转矩进行抑制,达到降低电磁转矩脉动的目的。首先,本文推导了PMSM运行的基波数学模型与谐波数学模型,分析了电磁转矩与谐波之间的关系,SVPWM原理及实现方式。其次,逆变器等的非线性特性使PMSM运行时电流中含有大量谐波,导致电流的畸变,电机运行在一定频率范围,电流的畸变会引起PMSM电磁转矩的脉动,产生纹波转矩,严重时可能导致系统不稳定运行。通过对逆变器中死区时间引起的电流谐波进行分析,提出电流预测法和电流矢量法来判断电流极性,通过时间脉冲补偿法来补偿死区时间导致的误差电压,从而抑制死区时间对电流谐波的影响。搭建基于时间脉冲补偿法的PMSM控制系统仿真模型,对比相同转速下死区补偿前后相电流波形、转速波形及电磁转矩波形分析,该死区补偿算法降低了电流中谐波成分,削弱了电磁转矩脉动。再次,齿槽转矩是PMSM的特有属性,在电机运行过程中同样会引起电磁转矩的波动,低速时更加的明显。本文通过有限元软件Ansoft对PMSM的齿槽转矩进行分析,得到齿槽转矩的周期性波动规律,利用傅里叶分解计算得到PMSM齿槽转矩各次谐波分量,通过公式的推导和计算,得到齿槽转矩与电流之间的关系。在搭建PMSM非线性模型和完成矢量控制仿真系统的基础上,加入齿槽转矩抑制模块,对齿槽转矩引起的转矩脉动进行抑制。其具体方法:采取注入交轴谐波电流,使得该电流产生的附加电磁转矩与齿槽转矩幅值相等、相位相反,以达到补偿的目的,降低齿槽转矩对电磁转矩脉动的影响。最后,在建立仿真模型的基础上,同时加入死区补偿算法与注入交轴谐波电流法,一方面抑制死区时间引起的电流谐波,另一方面抑制齿槽转矩的影响,进一步削弱了电磁转矩脉动,验证了该方法的合理性。
[Abstract]:High efficiency, high performance and low cost are the development trend of modern AC servo system. As an important link in servo system, permanent magnet synchronous motor (PMSM) has the advantages of simple structure, small size, high efficiency, reliable operation, wide speed range, good dynamic and static characteristics, and is widely used in industrial production, national defense, daily life and so on. However, the torque ripple of permanent magnet synchronous motor (PMSM) limits its application in high-precision situations, and the torque ripple also leads to the pulsation of rotational speed. Therefore, it is of great engineering significance to study the torque ripple suppression strategy of PMSM and increase the torque smoothness. In this paper, the ripple torque and grooving torque caused by electromagnetic torque ripple are suppressed from the point of view of control, so as to reduce the electromagnetic torque ripple. Firstly, the fundamental wave mathematical model and harmonic mathematical model of PMSM are derived, and the relationship between electromagnetic torque and harmonic, the principle of SVPWM and its realization are analyzed. Secondly, the nonlinear characteristics of the inverter make the current of PMSM contain a lot of harmonics, which leads to the distortion of the current. The current distortion will cause the ripple of PMSM electromagnetic torque and the ripple torque when the motor runs in a certain frequency range. Serious cases can lead to unstable operation of the system. By analyzing the current harmonics caused by dead time in inverter, the current prediction method and current vector method are proposed to judge the current polarity, and the time pulse compensation method is used to compensate the error voltage caused by dead time. Therefore, the influence of dead time on current harmonics is restrained. The simulation model of PMSM control system based on time pulse compensation method is built. The analysis of phase current waveform, speed waveform and electromagnetic torque waveform under the same speed is compared. The damned zone compensation algorithm reduces the harmonic component in the current. The electromagnetic torque ripple is weakened. Thirdly, the slotting torque is a special attribute of PMSM, which will also cause electromagnetic torque fluctuation in the motor running process, and it is more obvious at low speed. In this paper, the finite element software Ansoft is used to analyze the grooving torque of PMSM, and the periodic fluctuation law of the slotting torque is obtained. The harmonic components of the PMSM slotting torque are calculated by Fourier decomposition, and the formula is derived and calculated. The relationship between the torque and the current is obtained. Based on the PMSM nonlinear model and the vector control simulation system, the torque ripple caused by the tooth slot torque is suppressed by adding the gear slot torque suppression module. The specific methods are as follows: the additional electromagnetic torque produced by the current is equal to the slotting torque amplitude and the phase is opposite by injecting the alternating axis harmonic current, so as to achieve the purpose of compensation and reduce the influence of the tooth slot torque on the electromagnetic torque ripple. Finally, on the basis of the simulation model, the dead-zone compensation algorithm and the injected cross-axis harmonic current method are added to suppress the current harmonics caused by the dead-time and the influence of the tooth slot torque on the other hand. The electromagnetic torque ripple is further weakened and the rationality of the method is verified.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM341

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