Application Technology Of Compound Reactive Power Compensation Based On Distribution Network

Current motor,transformer and other nonlinear devices are widely used in power distribution network.A large amounts of reactive power is consumed by these devices.As a result,the power factor of the distribution network is low and the power quality is not stable.It is an important measure to add reactive power compensator to the secondary side of the transformer in order to improve the power factor of the distribution network.After determining the compensation location and selecting compensation mode,and analyzing the respective features of the thyristor switched capacitor(TSC)and the static var generator(SVG)in this paper,a compound reactive power compensation device combined with bothTSCand SVG is presented.TSC has the advantages of large compensation capacity and low cost,and SVG has the advantage of being able to emit reactive power continuously and quickly and can suppress harmonics in the grid.The combination of them can improve effectively the compensation accuracy and speed of the whole device.This paper has completed the design of the main circuit model structure of the compensation device and the calculation of the relevant parameters.In order to eliminate the interaction between TSC and SVG in the compound reactive power compensation device,the multi-agent coordinated control strategy is adopted in this paper to realize the large capacity dynamic compensation of the whole device.This control strategy is divided into three parts.It includes coordination part,reactive power control part and execution part.The design of the execution part is to select the hardware topology structure of TSC and SVG,in which TSC selects the triangle external connection method,and SVG selects the voltage type bridge circuit.The compensation for reactive power capacity is computed through analyzing the data of a shoe factory in south power network.The various electrical components parameters for the TSC and SVG and the grouping of the capacitor for the TSC are determined according to the required reactive power capacity.The coordination segment includes reactive current detection and reactive power distribution,and a zero-sequence current separation method based on instantaneous reactive power theory is adopted to detect quickly current.The control of reactive power is divided into the control of TSC and the control of SVG.This paper adopts the thyristor zero-crossswitching to control the TSC and avoid the shock current during the casting.the control method of direct current is adopted by SVG.On the basis of comparative analysis between the traditional PI control and fuzzy PI control,the variable universe fuzzy control of PI control strategy is presented because its DC side voltage's instability will have direct effects on the compensation effect of SVG.Finally,The modeling and simulation for TSC and SVG device are completed based on Matlab platform.The simulation experiments show the compensation characteristics of TSC and SVG.At the same time,it is proved that the PI control strategy based on variable universe fuzzy control can track quickly the setpoint voltage without overshoot and improve effectively the control performance and transient response performance of the system.