Robust Optimization Strategy For Reactive Power Configuration Of Multi-DC Infeed Receiving-end Power Grid

With the rapid development of DC transmission technology,while meeting the requirements of large-capacity transmission,the security and stability of multi-circuit DC feeds into the receiving-end power grid is also facing greater risks.The multi-infeed DC system has increased demand for reactive power,and the reduction of local traditional generator sets caused by incoming electricity from outside the area has weakened the system’s ability to resist reactive power disturbances to a certain extent.AC system failures often cause the DC system’s commutation bus voltage to drop,which in turn leads to the failure of the DC system’s commutation,which seriously threatens the safe and stable operation of the multi-infeed DC system.When the DC system is in the process of commutation failure recovery,the DC system needs to consume a lot of reactive power,which also brings greater pressure to the system’s reactive voltage regulation capability.In order to effectively solve the above problems,the configuration of reactive power compensation devices based on the accurate determination of the typical fault in the multi-infeed AC-DC hybrid system has become an important means to improve the dynamic reactive power support capability of the AC system,It is also of great significance to solve the problem of voltage stability of power grids in multi-infeed DC areas and to the safe and stable operation of AC and DC power grids.This paper mainly focuses on the non-linear robust fault estimation and reactive power compensation device configuration issues involved in ensuring the safe and stable operation of multi-infeed DC receiving end power grids.The main research work of the thesis is as follows:First of all,The traditional nonlinear robust fault estimation method is too conservative and the algorithm online calculation burden is too heavy,which is far from being able to meet the real-time detection requirements of a wide variety of faults in engineering.To solve this problem,from the two perspectives of reducing the conservativeness of fault estimation in nonlinear discrete systems and reducing the amount of online calculation of the algorithm,a robust fault estimation of discrete-time nonlinear systems based on the enhanced maximum priority switching law is proposed.new method.Based on the designed enhanced maximum priority switching law,the distribution type of the normalized fuzzy weight function at the current sampling time can be subdivided more flexibly.Then,according to the update value of the distribution type of the switching rule at the current sampling moment,the gain matrix of the fuzzy fault estimation observer in different switching modes is respectively input.The simulation results show that the proposed robust fault estimation method reduces the conservativeness of the method without adding additional online calculation burden,and has stronger robust performance against external interference.Secondly,in view of the problem of multiple DC feeds into the candidate points of reactive power compensation installation in southern Jiangsu,a reactive power compensation point layout scheme considering typical faults is proposed.The scheme first identifies the weak grid voltage area under typical faults,and secondly,the voltage In the weak area,the relative transient voltage drop area index is calculated and sorted through the cycle,and the candidate points of reactive power compensation under typical faults in southern Jiangsu are determined sequentially from the area to the station.This scheme can accurately identify the weak area of the power grid and accurately determine that it can give full play to the Power compensation efficiency site.Then,aiming at the problem of reactive power capacity allocation of multiple DC feeds into southern Jiangsu,a configuration scheme of reactive power compensation device to reduce the risk of multi-circuit DC commutation failure is proposed,and the risk of multi-circuit DC commutation failure is defined,considering each site at the same time constant capacity and separate constant capacity two schemes to configure the reactive power device,to reduce the risk of multi-circuit DC commutation failure and the lowest installation cost as the evaluation index,adopt VIKOR-based hybrid multi-attribute decision-making method to evaluate the different scheme of reactive power compensate.The device configuration plan is evaluated to determine the best installation plan and corresponding installation capacity.Finally,the simulation is carried out in the typical operation mode of the actual power grid to verify the effect of the method in this paper to reduce the risk of commutation failure.