It is anticipated that a large number of voltage source converters (VSCs) will be integrated into future power systems, which can potentially be detrimental to system stability. Previous work has utilized an impedance-based approach to analyze the feasibility region boundaries of power systems with multiple VSCs. However, impedance-based modeling limits the analysis of the system feasibility region to just two or three dimensions. Hence, this paper develops a methodology based on bifurcation theory that enables the system multi-dimensional feasibility region to be identified efficiently with consideration of multiple different varying parameters. The developed methodology is generalized so that it can be applied to identify system feasibility region boundaries in other power systems with multiple varying parameters. The partial Spearman correlation coefficient is adopted in this paper to identify the key parameters that affect the feasibility region boundary. Additionally, the calculated correlation indices quantify the interactions between the control loops VSCs in the system. The proposed methodology is verified against other analytical methods and the impact of key parameter variation on the system feasibility region boundaries is discussed.