A hexagonal hysteresis space vector current controller for single Z-source network multilevel inverter with capacitor balancing

Abstract

Z-source neutral-point clamped multilevel inverter (Z-NP-MLI) used in solar grid connected applications due to their better performance related to conventional inverters. Normally, current controller based Pulse Width Modulation (PWM) approach is expected for any grid connected system. The space vector pulse width modulation (SVPWM) strategy is a prominent modulation technique for Z-source multilevel inverters (MLIs) due to their appropriate voltage vector selection opportunity. Previous publications have shown the control of a ZNPMLI inverter using the SVPWM with and without modification of shoot through switching. However, the current controller based SVPWM is not attempted. This paper presents hexagonal space vector hysteresis current control (SVHCC) for ZNPMLI with DC-link capacitors balancing. This proposed SVHCC scheme uses reduced shoot through switching and finding the current reference based on the error. With respect to the error vector position, the choice of the adjacent vector is acted to minimize the error vector. In addition to the error vector selection, the capacitor voltage is also equilibrated by controlling the degree of freedom existing in selecting the switching vectors. The proposed scheme is asserted through MATLAB/Simulink and validated. The results are confirming the advantages of the proposed current control method and the line voltage and output current THD profile is lesser than conventional methods.