With　the　increasing　integration　of　power　electronic　devices,　a　growing　number　of　voltage　source　converters　(VSCs)　have　been　applied　in　the　power　system　as　an　interface　between　renewable　energy　sources　and　AC　power　grid.　However,　small-signal　instability　events　may　be　triggered　by　the　dynamic　interaction　between　VSC　and　power　grid　while　riding　through　voltage　dips.　Traditional　small-signal　instability　issues　of　grid-tied　VSC　system　can　be　investigated　by　bifurcation　analysis,　which　is　based　on　deterministic　eigenvalue　decomposition.　However,　when　certain　system　parameters　vary,　the　steady-state　operating　point　changes　as　well,　rendering　definite　analysis　inapplicable.　To　address　this　issue,　this　paper　proposes　an　interval　analysis　methodology　to　depict　the　varying　operating　scenarios,　obtaining　the　eigenvalue　locus　of　grid-tied　VSC　system　under　the　uncertainty　of　hyperparameters,　tackling　the　problem　of　the　system　small-signal　instability　with　multiparameter　varying　simultaneously.　Furthermore,　a　fifth-order　nonlinear　model　of　VSC　in　the　timescale　of　dc-link　voltage　control　is　constructed　in　this　article.　Eventually,　time　domain　simulations　on　a　grid-tied　VSC　system　are　conducted　to　verify　the　effectiveness　and　reliability　of　the　proposed　method.　©　2023　IEEE.