Reserch On The Optimum Allocation Of Voltage Sag Monitoring Nodes And Sag Source Location

Voltage sag is the power quality problem,affecting a large number of sensitive load's normally operating.Besides transmission and distribution network' fault in the power system will mostly cause the node suffering from voltage sags.Due to the short circuit's randomness,it is needed to stochasticly estimating the power system's voltage sag,besides,analying and evaluating voltage sag' state based on its results is the main content of researching power quality.For bringing the losses to a minimum,constructing a reliable and sensitive system to monitoring and locating voltage sag source,through stochasticly estimating the system's sag events,is of practical engineering significance.In order to meet the requirements of completely monitoring all sag events in the power systems,the simplest and most direct method is to install monitoring device in each bus node.However,power system has a large number of bus nodes,which not only increases the devices' cost,but also bring about the difficulty of data transmission and processing.Therefore,it is necessary to optimize the device configuration number and position.Besides the sag data information collected by limited-number voltage sag points are used to locate sag source,which can reduce the troubleshooting time and determine the responsibility for sags accident,in oader to ensure power supply reliability.This work in this thesis is as follows:Firstly,according to the different short-circuit fault types and the influnce of transformer,the voltage sags has been classified as seven types,and its effectiveness and feasibility have been verified in the simulation.Secondly,the voltage sag observation matrix is built,and the method of constructing observation matrix based on the virtual node is proposed.In this thesis the virtual node model is established,the fault distance has been introduced to construct the relationship between the fault distance and the node's voltage.Then setting the threshold value of the node voltage,the monitor reach area can be got through the virtual node method,in order to get the full network observability matrix.This thesis proposes the criterion of gaining node's reach area,and verifies this method.Thirdly,the linear programming model of monitoring point optimal configuration has been established,to meet the constraint conditions of completely monitoring sageventsand to make the amount of monitoring device as the objective function.A simulation is carried out to verify its effectviness in the IEEE test system through the branch and bound algorithm,considering the actual voltage rating and load capacity,the final optimization scheme has been determined.Finally,the method to locate the sag source through sag source judgment matrix is proposed in this thesis,the simulation of the radial grid verifies its effectiveness,but the method can only locate the fault region.To locate the specific location,the method to locate the sag source through using least square theory is proposed,and the simulation in the IEEE test system verify its effectiveness.