A two-level voltage source inverter (2L-VSI) when working under overmodulation regulation potentially has low performance, especially during large reference or load changes. To address this problem, a new calculation method is proposed in this article by determining a new reference vector from the boundary of linear-modulation zone as a best vector. The reference vector is synthesized by one or two vectors on the boundary line. Therefore, this technique simplifies the calculations to obtain the duty cycles and uses these duty cycles to identify the overmodulation zones. The proposed method is applied to the modulated model predictive control (MMPC) and the space vector modulation, respectively, in a 2L-VSI. A comprehensive assessment mathematically proves that both methods are in consistence with each other. Simulations and experiments are carried out to show that the proposed methods can reduce the computational burden and implementation complexity and improve the performance of the 2L-VSI in terms of fast dynamic response and smooth transition between the linear-modulation zone and overmodulation zone.