Improved Cost Function Definition for Fixed Switching Frequency FCS-MPC with SVPWM

The disadvantage of finite control set-model pre-dictive control (FCS- MPC) is that the switching frequency is variable and relies on the sampling time and operating point. This paper describes how to implement the fixed switching frequency functionality with FCS-MPC. This can be achieved by calculating the dwell times and selecting the optimal two active vectors for the next sampling interval, which have a significant impact on FCS- MPC performance during transient and steady -state conditions, and their values are determined using various mathematical models. Two cost functions are compared under the same conditions to verify their effect on the instantaneous values of the dwell times, and therefore on the FCS-MPC performance. This study considers two-level voltage source inverter for uninterruptible power supply (UPS) applications. The results obtained in MATLAB/Simulink reveal that tracking the voltage while ignoring its derivative results in low power quality. Including the derivative term can reduce the total harmonic distortion (THD) without a significant computational burden at the same switching frequency.