The third part of the work concerns the main influencing factors of the system low frequency oscillation , the small signal mathematical model of the inverter induction motor is established in the stator reference coordinate , effects of the motor parameter on the system low frequency oscillation are researched . then , by the analysis of the inverter nonlinear working characteristic , the internal relationship between the inverter dead time and the low frequency oscillation is studied and clarified , and the effects on the system low frequency oscillation are taken into account , which are produced by the dead time and change of carrier wave frequency of the inverter 首先建立了固定于定子坐标系中pwm逆变器-异步电动机小信号模型的基础，研究电机参数对系统低频振荡的影响；其次，通过逆变器非线性工作特性的分析，研究并揭示了逆变器死区时间与系统低频振荡的内在关系，考虑逆变器死区时间、载波频率的变化对系统低频振荡的影响；最后总结出提高和改善系统稳定运行的电机设计和逆变器v / f _ c曲线设置准则。
