计算长电缆电机端电压的递推算法

Recursive Algorithm for Calculating Motor Terminal Voltage with Long Cables

针对变流器与电机间由长距离电缆连接时机端过电压问题,提出根据单程传输时间前的变流器电压和往返传输时间前的电机端电压而递推出当前电机端电压的方法。利用该方法,首先推导出在已知变流器输出梯形波的情况下,电机端电压的表达式。然后,严格论证了在上升时间之后的一个单程传输时间点电机端电压取得最大值,并给出电机端电压与上升时间的关系曲线。说明了电机端电压的最大值并不是变流器输出电压上升时间的单调递减函数,而是周期性地增减。相比于行波反射理论,所提出的方法更便于定量分析。最后,通过仿真和在双馈风力发电机变流器系统中实际观测的电压波形对比,说明所提结论的正确性。

Aiming at terminal over-voltage of the motor when connected to the converter with long cables, proposed an algorithm for calculating the motor terminal voltage based on the output voltage of the converter one transmission time ago and its own value a return trip before recursively. Firstly, according to this method, the motor terminal voltage expression was derived when the trapezoidal wave of output voltage is known. Secondly, a conclusion that the motor terminal voltage gets to its maximum at the time required for a trip from the converter to the motor after rise-time was proved strictly. Moreover, the relation between maximum motor terminal voltage and rise-time was illustrated which shows that it is not monotone decreasing but periodic oscillation. Compared with conventional traveling wave and reflection theory, the method proposed is more suitable for quantitative analysis. At last, the theoretical results are validated by comparing emulation with experimentation in doubly-fed wind-energy system.