Finite set model predictive control (FS-MPC) has shown the features of a simple and practical method in power electronics application. Increasing the number of the voltage vectors in FS-MPC is useful to reduce the harmonic distortion of currents, and the voltage and the torque ripple. Despite all of the advantages this method has a high computation burden. For the vector increase, due to expenses of multi-level inverters, i.e., hardware solution, the discrete space vector modulation, i.e., software solution, is used in lower power applications. Reducing the number of feasible vectors in the cost function is a challenge. In this paper, a new method is proposed for fast and easy detection of the triangle that the reference voltage vector is located. The method uses the magnitude and the phase angle of the reference voltage. By this method, the process of determining the closest three vectors is eased. The validity of the proposed method is verified by the simulation.