量化误差对电厂主汽温控制品质的影响

Influence of quantization errors on control quality of main steam temperature control systems of power stations

量化误差主要与量化单位量成正比。量化单位量的大小取决于A/D或D/A的转换器的位长。量化误差将影响控制系统的准确性指标。对于电站锅炉主汽温控制系统,一般选择12位或16位的A/D或D/A转换器就可满足要求。量化器是典型的非线性环节,可能给控制系统带来自振荡、突变扰动等降低控制品质的影响。一定大小的均匀白噪声的存在,可抵消量化误差的负作用。仿真试验表明,选择偏高精度的A/D转换器,并不意味着可得到较大的控制品质改善。

The quantization error is directly proportional to the quantization unit value, while the quantization unit value depends on the number of digit bits of an A/D convertor or a D/A convertor. The accuracy performance of a control system is probably affected by the quantization error. For the main steam temperature system in power stations, it is suitable to select 12 or 16 bits A/D or D/A convertors. The quantizer is a typical non-linear element, and so it may lead to control quality dropping with unexpectedly disturbance of self-oscillation. If there is white noise with proper strength, the bad effect of the quantization error can be cancelled out. The simulation results show that selecting the higher precision A/D convertors does not mean getting great improvement on the control quality.