Research On Line Parameter Error Hypersensitivity Of Reactive Power Flow In The Complex Large-scale Power Grids

With a gradually larger scale of modern power grids, increasing difference between loadpeak and valley, constantly concentrated EHV transmission lines, and increasinglycomplicated reactive power characteristics, the reactive voltage regulation and control playsan increasingly important role in the power system. Reactive voltage regulation and control isachieved by AVC system which is based on the calculation of reactive power optimization.Reactive power optimization calculations must rely on the accurate power flow calculation.The complex large-scale power grids which contain super/ultra-high voltage equipment arevery large, while the whole network is coupled tightly, and the reactive characteristics ofhigh-level grids are strongly capacitive. An error in parameter of the mathematical model willlead to significant mistake in flow calculation results. Cumulative error in the calculation ofreactive power loss is particularly evident, which will affect node voltage and reactive poweroutput of balance node and PV nodes, and consequently mislead the regulation and control ofreactive voltage in the complex large-scale power grids.In this thesis, the author focuses on the significant demand of the hypersensitivity studyon line parameter error of the reactive power flow in complex large grids, referring toavailable research literature to understand the research background in depth, systematicallyanalyzing the problems in the calculation of reactive power in complex large grids and widelyintroducing the research background at home and abroad. For the distributive characteristicsof super/ultra-high voltage power transmission line parameters, this thesis stresses thenecessity of the use of distributed parameter in circuit modeling and describes the short line,medium line and long line equivalent circuits. Meanwhile, the factors affecting parametervalues in the power transmission line model are studied and the existence of the parametererror is primarily proved.To further clarify the relationship between the error and the trend line parametercalculation, this thesis describes the voltage drop and power loss transmission lines, andfurther demonstrates the close ties among the transmission line voltage drop, power loss andtransmission line model parameters R, X and B. 220 k V and 500 k V reactive power lossmechanism for the transmission line are discussed respectively in this article, and the reactivepower loss mechanisms 500 k V transmission line is discussed.In this thesis, taking 500 k V UHV power grids of a southern province as an example, theauthor uses simulation software for flow calculation and simulative analysis and when theparameters generates 10% error trend analysis, the main evaluation indicators include 500 k Vbus voltage and reactive power balance node and PV output node. The results of simulationshow that complex large grids reactive power flow is hypersensitive to error of transmissionline. Among the three parameters resistance, reactance, and capacitive of Transmission Line,capacitance error is the most influential to flow calculation results and plays a leading role inflow calculation. Because load fluctuations lead to the phase-to-ground distance and becausedistance change, different geographical environment, changing weather and other factors willlead to a significant line capacitance parameter error, consequently, there will be a tremendousdeviation in the power flow calculation results of the large-scale power grids, and evennon-convergence trend in extreme cases. Research on line parameter error hypersensitivity ofreactive power flow in the complex large-scale power grids in this thesis will be practical anduseful to solve the problem that the simulation of reactive power flow in complex large-scalepower grids is difficult to converge.