中文摘要：

从方差的意义上对串级控制系统的控制性能进行了评价．根据反馈不变项理论，得到串级控制系统在最小方差控制器作用下的输出表达式，该表达式可通过采用时间序列模型进行拟合，从而可建立噪声到输出的时间序列模型．根据此模型可求出串级回路输出最小方差的估计值，将该估计值作为基准与实际的输出方差进行比较，得到最终的性能指标．结果表明：这种方法无需辨识过程对象精确的模型，而且计算方法简便、实用．笔者将利用此方法得到的性能指标与某电厂600Mw机组主蒸汽温度控制系统的实际数据进行了对比分析，验证了该方法的可靠性和准确性．

英文摘要：

According variance, control performance of cascade control loop was assessed. Output expression of cascade control system under minimum variance control was obtained based on feedback-invariant terms theory. The output expression can be fitted by time series model, so a time series model of the process from white noise to output was built. Based on this model, the estimated output minimum variance of cascade control loop was calculated. Taking the minimum variance as reference, the practical variance of system output was evaluated, from which the control performance index was obtained. Results show that, it is not necessary to identify the precise process model, the algorithm is simple and feasible. Comparative analysis between practical data from main steam temperature control system of a 600 MW power unit and the data obtained by this method proves reliability and validity of the method.