负电流 meaning in English

negative current

There are five parts are as follows : in part one , the concept of switching function is introduced first to establish the nonlinear mathematical model of the induction motor variable frequency speed adjustment system which is fed by a sine pulse width modulated ( spwm ) inverter and takes the effect of the main magnetic circuit saturation into consideration , then the low frequency oscillation of the system is simulated according to the model . next , from the view point of energy conversion of the inverter - induction system , a criterion for the low frequency oscillation is proposed to determine whether the system is in low frequency oscillation which is judged by whether the interval of the negative current component of the inverter input current is more than 1 / fc ( fc is the carrier wave frequency of the inverter ) or not
首先引入开关函数概念，建立了正弦脉宽调制( spwm )逆变器供电异步电动机，考虑主磁路饱和时的变频调速系统整体数学模型，模拟系统的低频振荡；其次从逆变器-异步电动机系统能量转换角度出发，提出通过检测逆变器输入电流中负电流的间隔时间是否大于1 / f _ c ( f _ c为逆变器载波频率)来判定系统是否出现低频振荡；最后的实验结果验证了系统低频振荡建模和判据的实用性和正确性。