Transformerless Three Phase Variable Output Voltage DC/AC Standalone Power Converter Using Modified Restrictive Control Set Model Predictive Control

This paper proposes a new technique for regulating the amplitude of line-line voltage of a voltage source converter (VSC) with standalone linear or nonlinear load by using the concept of restrictive control set model predictive control (RCSMPC). Conventionally, the line-line voltage is regulated by regulating the amplitude modulation ratio (ma) in sinusoidal pulsewidth modulation (SPWM) technique. However, the total harmonic distortion (THD) increases with the decrease in ma. Moreover, the conventional approach also has some restraint in the large settling time. This problem is addressed by suggesting RCS-MPC for controlling the amplitude of line-line voltage of VSC. Through RCS-MPC, the value of slider gain in the cost function is adjusted accurately to regulate the output line-line voltage. The proposed approach increases the linear region from 0.612 to 0.648, limits the THD of output voltage below 5% during the variation in the output voltage from zero to the maximum value. From the proposed approach, settling time reduces from 0.035 s to a minimum of 0.005 s. The use of the restricted control horizon ensures a low computational load by undergoing the computational time complexity analysis of the MPC algorithm. The stability analysis is performed using the phase portrait and the effect of parameter variation is also discussed. The practicability of the recommended method is verified by MATLAB/Simulink and it is also verified experimentally.