Research On Application Of State Estimation In Reactive Power Optimization System Of Distribution Network

In electric power dispatching, the reliability of reactive power optimization systembecomes more and more strict accompanied by the power users`increasing demand for thevoltage quality and qualified rate of power factor. The completeness and accuracy of theSCADA(Supervisory Control and Data Acquisition) measurement data, which are collected bythe existed distribution network reactive power optimization system in real time, is low. Andthe grid operation state error is large when the optimizing process is being implemented, such asORPF(Optimal Reactive Power Flow) calculation, on the SCADA measurement data directly,which leads to the low reliability of VQC(Voltage Quality Control) reactive power and voltageupper and lower limit, as well as the low capability of implementation of compensation deviceaction plan gotten from the further time partition and load forecasting. This paper presents theapplication of state estimation in distribution network reactive power optimization system toimprove the measuring accuracy and completeness, in order to improve the reliability of systemreactive power optimization.In an actual distribution network connection, the related equipment files are input into thesystem database, which will access the device files to calculate the parameters, mainlyincluding transmission lines and the equivalent impedance of transformer. For the controlobject of reactive power optimization system, after forming the topological relationship, thispaper adds the transformer stalls and capacitor capacity into the model as the control variables,which can make the state estimation to calculate the real-time state of power grid more accurateand be regarded as the foundation of the further ORPF calculation. In order to reduce the theinjection elements appeared in the triangular decomposition of node admittance matrix whenthe system is calculating, this paper numbers the system nodes according to the minimum outletbranch number after considering the increased line number and calculation workload in theprocess of node elimination. Considering the influence of external network, in order to ensurethe accurate state estimation, this paper uses the classical extended Ward equivalent method todo the equivalence calculation for external power grid, such as Jining power grid. Theregulation of voltage and reactive power for one transformer substation can influence otherassociated voltage substations. This paper divides the whole network into power supplysections according to the bus incidence matrix, which provides the basis for the soft VQCaction plan.After the equivalent model is formatted, the data matrix is formed as a characterization ofnetwork equivalent model with the tool Matlab. Simulations and analysis are implemented in combination with the measuring analog on state estimation algorithm, and apply the stateestimation algorithm to the practical reactive power optimization system is applied. After thestate estimation analysis on the actual application results, the conclusions are as follows: thevoltage amplitude of load flow calculation is more closed to the measured values, and thecalculation error reduces significantly; the vast majority of power flows after power flowcalculation are more closed to the measured values and the calculation error reducessignificantly; the detection of bad data meets to the real-time running status.Based on the realization of state estimation algorithm, the offline and online optimizationof state estimation in reactive power optimization is elaborated and the system flow for the twooperations is explained. After estimation of measured data according to the state estimation, themost advantage of the bus voltage and reactive power in the optimal time will be attainedthrough the optimization calculation. Also the voltage and reactive power limits will be gottenalso through further combining load forecasting, which are then sent to the VQC module as thebasis of the action implementation. Compared to the power grid before installing the system,under the same load fluctuation condition, this system has the bus voltage level raised greatly,the power factor yield improved, the number of equipment action effectively reduced, and thepurpose of loss reduction and energy saving achieved.