Study On Wide-area Backup Protection Based On Estimation And Node Fault Injection Current Under Limited PMUs

With the development of smart grid and ubiquitous electric power Internet of Things,the structure of the power grid becomes more and more complicated.Traditional backup protection based on local information has the disadvantages of difficulty in setting the protection,protection malfunction,long protection action time,etc.,and it is difficult to ensure the reliability of power grid protection.Protection algorithm using global information can be a powerful supplement to traditional backup protection.As the core component of wide-area protection,PMU can simultaneously measure the electrical quantity information at the protection installation.However,PMU is expensive and cannot be arranged on all buses in consideration of economics.Therefore,this article mainly studies the wide-area transmission line based on limited PMU configuration.Backup protection algorithm.The common structure of wide-area backup protection system is introduced,and the characteristics of various structures are analyzed.Then the fault area detection method in wide area backup protection algorithm is introduced,which provides the suspected fault lines for the fault detection algorithm proposed in this paper.Firstly,this paper introduces the working principle of three kinds of wide area backup protection systems,and analyzes their advantages and disadvantages in detail.Then two common fault area discrimination methods are introduced.Finally,PMU layout based on fault observability is introduced,which lays the foundation for the later two chapters of this paper.In this paper,a transmission line fault detection algorithm based on the combination of a finite phasor measurement unit(PMU)and double-ended ranging is presented.The interval bus is used to arrange the PMU strategy,and the network is divided into several areas.Estimate the total estimated current of the un-arranged PMU bus,detect the suspected fault area based on whether it exceeds the threshold,and use t-test to check and correct the data asynchronously for the suspect area;use each PMU data to obtain the un-arranged PMU bus more accurately The positive sequence of the estimated voltage and the current flowing to the fault line are calculated using the two-terminal ranging principle.The fault distances of the suspected lines are calculated respectively.The range of fault distances for the fault line and the normal line is theoretically analyzed.Fault detection and location criteria for transmission lines under PMU.For bus faults,the bus differential protection is used as an auxiliary criterion.Multiple examples of 39-node system verify the effectiveness of the algorithm,which can correctly detect faulty lines without being affected by fault location,fault type,and transient resistance.When there is a certain error in the line parameters,it still has high detection accuracy and anti-synchronization ability.A wide-area backup protection algorithm based on node fault injection current under limited PMU is presented in this paper.Under the strategy of arranging PMUs in spaced buses,the fault area is first determined according to the wide area differential method.Then the fault component of the voltage of each bus node and the node injection current in the fault area under the interval bus layout is calculated.The node fault injection current is constructed through the derivation of the node voltage equation,and the failures of the nodes on both sides of the fault line and the normal bus node are analyzed.The variation characteristics of the injected current at the back node fault,and based on this,the protection criterion is constructed.On the basis of detecting the faulty line,the location of the fault point can be further obtained.It is not affected by the transition resistance and the fault type,and the fault location has high accuracy.Multiple cases of 39-node system verify the effectiveness of the algorithm,which is not affected by fault location,fault type,and transient resistance.It can still detect faulty lines in scenarios such as switching faults,system oscillations and faults,non-full-phase operation and faults,and the presence of Gaussian white noise.