Research On Evaluation Index Of Receiving-end System With Multi-infeed HVDC Including VSC-HVDC

With the development of power electronics technology and the increasing safety and stability of traditional LCC-HVDC multi-infeed systems,VSC-HVDC began to appear in multi-infeed systems,forming a multi-infeed system with VSC-HVDC.The original multi-infeed system evaluation index is no longer applicable,and new indicators are needed to describe the multi-DC feed-in system with VSC-HVDC.This paper mainly focuses on two aspects: 1.Evaluation index of system strength of LCC-HVDC receiving end in VSC-HVDC multi-DC feed system;2.Interaction evaluation index of VSC-HVDC multi-DC feed system.Firstly,the power stability of LCC-HVDC is analyzed,and an indicator for evaluating the strength of LCC-HVDC receiver-end system is proposed--receiver system voltage intensity factor RVSF.This indicator can take into account the power of receiver system such as VSC-HVDC.The impact of system components.The critical value of RVSF,CRVSF,is defined by the power stability limit condition of LCC-HVDC.The calculation method of CRVSF is given,and the criterion for distinguishing the strength of the receiver system using RVSF is given.The analytical derivation and the simulation of the example show that the power stability and static voltage stability of RVSF and LCC-HVDC are closely related,and the given RVSF threshold is accurate and feasible.The effect of VSC-HVDC on the strength of the LCC-HVDC receiver system was analyzed using RVSF.The RVSF analytical calculation method was proposed and verified.This calculation method was used to analyze the influence of the transmission power and the drop point of VSC-HVDC on the strength of the LCC-HVDC receiver system under the two control methods.The conclusions obtained from the research can be used to guide the operation and planning of the VSC-HVDC system.The mutual influence law of multi-infeed system with VSC-HVDC is studied.From the perspective of steady-state operation,the influence of feed power at different placement points on the voltage of a bus is described.A MIIF calculation method that considers the control method is proposed.This method is given in the form of a simple analytical formula,which does not need to consider the influence of the power flow.That is,the accuracy of the control method is increased,the calculation is simple,and the analysis is convenient.The simulation example shows that the calculation method is accurate and can take into account the effects of VSC-HVDC.Using this MIIF calculation method,the reactive-voltage characteristics of VSC-HVDC and LCC-HVDC are studied in parallel,and the variation of MIIF with various influencing factors is studied.Among them,the degree of influence of reactive-voltage characteristics on MIIF was studied.The study has obtained many useful conclusions and can be used to guide the planning of VSC-HVDC.