Sliding Mode Control for Cascaded Multilevel Inverters

This paper presents a new sliding mode control method (SMC) without carrier techniques for using traditional cascaded H-bridge multilevel inverters (CHBMLI). The sliding surface is designed to squeeze the object located on the sliding surface. Moreover, using a low-pass filter to reduce oscillation (chattering) around the sliding surface due to rapid change and large amplitude of current and voltage of the load is presented. A current control based on sliding mode control method is applied for nine level cascaded H-bridge multilevel inverter. The load current is controlled by the desired current. Without carrier and only level comparation, it makes for simple algorithms, less memory, reduces the number of switching so the losses of switching process of components are also decreased. In addition, due to not using carrier, the chattering is avoided, caused by the carrier in the inverters, reduces Common-Mode voltage (CM) and controls well in case of unbalanced source. Simulation and experiment on MATLAB/Simulink have been used to verify. The experimental results have shown the current follows the set value from low to high in both cases the balanced and unbalanced of DC sources, reduces Common-Mode voltage, reduces the number of switching. The results also show that when without carrier, then the filter parameters greatly affect the quality of the inverters.