Research On Dynamic Evaluation Index Of Voltage Support Capability Of Receiving-end Power Grids With Multi-infeed HVDC

North China,East China and South China have built a typical multi-infeed AC/DC hybrid power grid.The HVDCs’ electrical connection of this type power grid is tight.Once receivingside AC system fails,it can easily leads to a single or even more than one inverter commutation failure.If the voltage support capability is insufficient during the recovery process,it will cause the HVDC blocking and power shortage which will make receiving-side system produce the serious stability problem of voltage and angle.Therefore,it has great significance for the planning and operation management of AC/DC power grid to study the comprehensive effect of multiple HVDC dynamic behavior on power grid security and establish the effective evaluation index.At present,the research of corresponding index,that is,Short Circuit Ratio(SCR)has majorly focused on static voltage stability analysis field,and there is few research to discuss the effect of power system dynamic process on the index,which makes the index of application in the engineering lack of convincing.This paper firstly introduces the analysis method of Effective Short Circuit Ratio(ESCR)in static voltage stability analysis field,that is,the relationship between ESCR and maximum power curve.Then under the premise of considering the dynamic process of HVDC,the changes of ESCR critical value under the influence of different factors is discussed,and the critical value of ESCR considering HVDC dynamic characteristics is recommended.Then based on the application scope of Multi-infeed Effective Short Circuit Ratio(MIESCR),the paper further puts forward the applicable condition of ESCR in multi-infeed system,and points out that ESCR and MIESCR respectively specifies the upper and lower bounds of the voltage support capability.Based on the conclusion,the MIESCR is revised,and the dynamic index,that is,Generalized Multi-infeed Effective Short Circuit Ratio(GMIESCR)is presented which can evaluate the voltage support ability of multi-infeed system in different disturbance scenes.The critical value changes of ESCR,MIESCR and GMIESCR under the influence of different factors is discussed in the CIGRE HVDC standard testing system and dual-infeed system with two generators under the PSCAD environment,the superiority of GMIESCR is verified through comparing above results,and the threshold system of GMIESCR is proposed.Finally,the influencing factors and changes of disturbance parameters evaluating disturbance intensity in GMIESCR is roundly discussed in the dual-infeed system,and the simplified calculation scheme for this index is proposed,which provides access to possibility of estimating voltage support ability rapidly.This index can be applied to the selection of HVDC landing in the planning stage of power grid,the improvement of operation condition of AC/DC hybrid power system and so on,which has certain guiding significance for operation stability of AC/DC hybrid power system.