本文根据步进电视的结构与控制原理，提出一种PWM式相矢量合成分数步距角控制方案。

Based on the construction pattern and the control principle of stepmotor, fractional step Angle control of stepmotor is achieved by PWM Phase Vector Cornposition.

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该方法通过实时检测三相交流输出电流方向得到方向函数，利用该函数选择一个PWM周期内不同电压矢量作用时间来控制中点电流的方向，实现电压平衡。

By getting the direction function from the output AC current, the applied time of voltage vectors in one PWM period was chosen, the direction of central current was controlled for DC voltage balance.

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针对三相异步电机矢量控制系统的要求，根据在静止坐标系统中异步电机的数学模型，进行了系统仿真。

The thesis introduces a three phase AC motor's mathematical model in static reference frame and a simulation system for AC motors to develop a vector control inverter system.

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Actually, the view of vectors we take nowadays is that vectors are associated with a pair of numbers which, on the rotation of axes, transform like this.

实际上,今天我们讲矢量所用的观点是,矢量是和一组坐标值相对应的,在坐标轴旋转的过程中像这样变换

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