Research On State Estimation Of Distribution Network Based On PMU Measurement

With the development of society and economy,the demand for power supply reliability,safety and power quality is higher and higher.Therefore,the evaluation of the operation state of the distribution network directly to the user is extremely important.Distribution network state estimation is from the measurement system to the distribution control center is very important part of the distribution network state estimation algorithm instead of the traditional calculation of power flow calculation is not accurate,the line faults,redundant measurement system using real-time data,improve the accuracy and automatically exclude the interference caused by the random error data,estimate system state.In order to obtain relatively accurate measurement data,it is necessary to install phasor measurement units,advanced metering architecture and other advanced measurement monitoring devices in the distribution network.Compared with traditional measurement equipment,PMU can measure the node voltage and branch current of the power grid,and also can directly measure the phase angle of voltage and current,and the measurement accuracy is greatly improved.PMU uses GPS communication technology to synchronize measurement data at the same time point.But the installation cost of PMU is very high,so it is seldom used in the distribution system with many nodes.This paper focuses on the three-phase state estimation algorithm of distribution network based on measurement transformation technology after installing a small amount of PMU.Since PMU has relatively high measurement accuracy and small measurement error,the data should be given greater confidence(greater weight).The pseudo quantity measurement is based on historical data,and the measurement error is larger,so the confidence is lower(the weight is smaller).In this paper the node voltages and branch currents as state variables of the weighted least squares state estimation algorithm,the standard node system allows measurement transformation state estimation algorithm and weighted least squares method for comparative analysis.In transmission network,the optimal allocation of PMU is mostly based on the observability of whole network.Because the distribution is closed loop design,open-loop operation,the number of nodes is large,so it is impractical to make the distribution network reach the whole network.In this paper,the distribution state estimation accuracy and the minimum installation cost of PMU as objective function,using the improved hybrid genetic simulated annealing algorithm to optimize the configuration of PMU,and compared with the optimal algorithm of single node,using IEEE33 system to validate the algorithm.