Research On Distribution System State Estimation Based On Uncertain Measurement Information

With the development of renewable energy technology and the increase of measurement divices equipped in the distribution network,more uncertainties need to be considered in distribution system state estimation(DSSE).Besides,with the dynamic changes of distribution system becoming more and more frequent,the traditional measurement data based on poor accuracy and low sampling frequency can not meet the requirements of real-time monitoring of distribution system.And the introduce of Phasor Measurement Unit(PMU)brings more chances and challenges to DSSE.Based on the above situation,the DSSE is studied in this paper,and the main work is as follows:(1)Aiming at the situation of the exsistence of bad data and low redundancy of real-time measurements in distribution system,the Institute of Geodesy and Geophysics III(IGGIII)robustness scheme is used to divide the measurement data into normal,suspicious,and harmful segments so that the corresponding weights are divided into the preservation zones,decentralized zones,and elimination zones.Besides,to eliminate the effect of bad data duiring iterations,the standard residual method is introduced,and the robust thresholds are adjusted adaptively.(2)Aiming at the situation of low accuracy and refresh frequency of traditional measurement data,a hybrid state estimator based on supervisory control and data acquisition(SCADA)and phasor measurement unit(PMU)measurements is proposed in this paper.According to the data acquisition time,the state estimator switches between the robust estimator and the linear estimator to fast track states,which effectively guarantees the timeless of PMU measurements and correct the estimation results in time.(3)Aiming at the situation of only knowing the upper and lower limits of uncertainties,an interval state estimation for distribution system is proposed,which describes these uncertainties of system measurements are quantitatively d by the interval numbers and affine arithmetic.In order to accurately obtain the results of DSSE,an algorithm based on the combination of interval arithmetic and affine arithmetic is proposed.In this method,the interval numbers and affine arithmetic are transformed into each other in the iterative process to reducing the conservatism of interval state estimation.The estimation results in interval form are used to provide upper and lower bound information of DSSE results for dispatchers more intuitively.