Design and control of novel grid tied multilevel filter-less inverter using current based sliding mode control

Abstract

The role of control techniques is increasing due to the high penetration of renewable energy sources at grid level. The importance of inverters also rises as it balances the supply between the renewable source and grid power system. The issues related to penetration of renewable energy like power quality maintenance, protection against the detection of islanding and maintaining the integrity of grid; control techniques play a vital role to solve these problems. This paper proposed an internal control technique known as current based sliding mode control (SMC) for a filter less multilevel inverter (MLI). The aim of proposed research work is to achieve 27 level output voltage by using an inverter, which approaches sinusoidal wave without using any filters. To control the output of MLI, a current based SMC is implemented in order to achieve the robustness, a good dynamic response, a smaller number of voltage ripples and a smaller current THD. Moreover, a comparative analysis of SMC is done with the conventional PI controller. The response of the controller has been investigated for different cases e.g., introducing sag, swell, faults and harmonics in grid level has been implemented on MATLAB/Simulink. To validate the results of SMC for MLI, an experimental setup was also established which consists of National Instruments (NI) based hardware in loop (HIL) system and dSPACE 1202. The HIL system results show consistency with simulation results.