Direct power control (DPC) has been proposed as an effective control method for pulse-width modulated (PWM) converters. The recent development focuses on the integration of the model predictive (MP) control and DPC to obtain better steady-state performance. In most MP-DPCs, duty cycle optimization (DCO) is a common technique to achieve the power error minimization. However, the periodic occurrence of a duty cycle larger than one ("D > 1") deteriorates the performance of the PWM converter by inducing current spikes and power surges. To address this problem, this paper conducts an in-depth examination on the "D > 1" case common in MP-DPC using DCO. It is found the "D > 1" is caused by the wrong control action of the active power in the starting period of each sector. Furthermore, a new table containing an additional pre-calculated interval in every sector is developed to eradicate the "D > 1" case and its associated power quality issues. Both simulation and experimental results are included to demonstrate the effectiveness of the new table.