Research On The Realization Of The Control About Crossing-region Interconnected Grid

With the development of UHV AC and DC projects,China has formed the North China Central China UHV AC weak synchronous network pattern.With the access of Tianzhong and Qishao UHV DC,the central China Power Grid with the characteristics of cross regional interconnection and large grid has the characteristics of DC transmission end.The access of Jin Su,Fufeng and binjin UHV DC makes the southwest power grid a large transmission end power grid,Chongqing The back-to-back DC operation of Hubei province transforms the synchronous interconnection characteristics of central and southwest China into asynchronous interconnection characteristics.Therefore,based on the cross regional interconnected power grid as the main research object and the background of practical engineering,this paper studies the frequency stability,voltage stability and out of step oscillation caused by the UHVDC blocking fault of synchronous interconnected power grid and asynchronous interconnected power grid.At the same time,different from the traditional independent stability control system,this paper puts forward multi resources.The architecture of the source coordination emergency control system is applied in practice.The main contents of this paper are as follows:(1)In this paper,a fast configuration method based on single machine single load model is proposed for the over-frequency tripping generator scheme of cross region interconnected power grid without the scheme.First of all,by deriving the analytical expression of the frequency fluctuation characteristics of the system after the disconnection of the cross regional interconnected power grid,the dynamic characteristic curve of the system frequency is obtained under the condition of considering the function of the system standby and the governor;secondly,the influence of the load model,the active frequency factor of the load and the governor characteristics on the frequency change of the system is studied,the frequency influence correlation factor is constructed,and these three factors are quantified and defined It is the main factor of frequency characteristics;then,based on the practical configuration principle of high-frequency cut-off of cross regional interconnected large power grid,a single machine single load model is constructed to quickly configure the fixed values of various parameters of high-frequency cut-off,including frequency threshold,time delay,minimum cut-off load,load ratio of each round,etc.Finally,through the verification and fine-tuning of the whole model of large power grid,the practical effect of the scheme is good.(2)In this paper,a multi scenario and multi-objective low-frequency load shedding optimization model is constructed,taking into account the various fault scenarios of the trans regional interconnected power grid.First of all,the optimization space of load shedding and steady-state frequency recovery effect of cross regional interconnected large power grid is clarified;secondly,considering that there are many variables that can be optimized in the low-frequency load shedding scheme,the optimization variables are determined as the load shedding ratio of basic and special rounds according to the optimization objective of load loss reduction;then,the objective optimization function is determined to average At the same time,the load cut-off rate,the limit range of frequency dynamic fluctuation,the steady-state recovery frequency and the time needed to recover the steady-state frequency are taken as the constraints.Combined with multiple fault scenarios that cause the low-frequency problem of cross regional interconnected power grid,based on NSGA-II algorithm,the optimization calculation is carried out to provide the optimization of low-frequency load shedding strategy Theoretical guidance to achieve the goal of load loss and average frequency deviation double drop.(3)In this paper,based on the two machine model’s local operation trajectory and the law of oscillation center migration,an optimization method of out of step oscillation splitting constant value configuration strategy for cross regional interconnected large power grid is proposed.Firstly,the two machine model is constructed,the out of step splitting criterion mechanism based on local quantity is deduced,and the running track of measuring point voltage,impedance,phase angle and oscillation center voltage is obtained;secondly,the simulation model of oscillation splitting device based on impedance angle principle and oscillation center voltage principle is established through the comparison of action principle of splitting device and three impedance principle of generator protection The simulation accuracy of the operation of the train device is known.Then,by analyzing the migration law of the oscillation center of the power grid,such as the continuous migration of the oscillation center and the large-scale transition,and the influence of the factors such as machine cut,load cut and system disconnection on the migration of the oscillation center,the optimal adjustment and configuration of the interlocking operation of the out of step splitting device of the cross-section of the inter province interconnected large power grid are proposed.(4)Based on the frequency,voltage and out of step emergency control technology of cross regional interconnected power grid,the system protection architecture of improving the first line of defense,expanding the second line of defense and optimizing the third line of defense is proposed,and the configuration scheme of multi resource coordinated emergency control system is proposed,and the overall construction scheme of multi resource coordinated control system is proposed at the initial stage of system protection implementation.