一种交流调速的高精度采样系统设计

Design of High-precision Sampling System Based on AC Variable Speed Control

基于TMS320F2812内部自带ADC模块的优缺点分析,探讨扩展ADS8365的高精度采样系统设计,以求提高整个系统的测量和控制精度,实现数字化变频调速系统中对多路电压、电流、转速等信号的高精度采样.讨论了影响TMS320F2812芯片A/D转换器精度的原因,给出了ADS8365芯片进行电流信号采样的电路设计,并通过仿真和实际电路实验说明了电路设计的有效性.相比于TMS320F2812的单端采样,基于ADS8365的采样电路具有采样精度高、速度快、同步性好、失真小、抗干扰强,同时能够较好的抑制温漂和热噪声等明显优势.将该采样电路应用于本交流调速系统中,不仅可以大大提高系统的采样精度,增加系统的抗干扰性,也便于系统工况的实时分析,进行合理控制及实时保护.

In this paper, the advantages and disadvantages of the built-in ADC module in TMS320F2812 is analyzed, and high-precision sampling system based on the AD8365 is studied for improving the measuring and controlling accuracy of the whole system, as well as achieving highprecision sampling involving multi-voltage, current, and speed in digital variable frequency variable speed system. Finding out the causes affecting the precision of TMS320F2812 AD converter, the authors work out the current circuit design of current signal sampling, using ADS8365, and prove the effectiveness of the design by way of simulation and practical current circuit experiment. As compared to single-ended sampling of TMS320F2812, differential sampling circuit based on ADS8365 has more advantages： high precision, high speed, good synchronization, small distortion, strong anti-interference, and providing such significant qualities as better suppression of drift and thermal noise. Adopting the sampling circuit in the AC speed control system not only greatly improves the sampling accuracy of the system and increases the system immunity to interference, but also facilitates real-time analysis in system operating conditions, and implements reasonable controlling and real-time protecting.