Asymmetrical Three-Phase Multilevel Inverter for Grid-Integrated PLL-Less System

Nowadays, the conventional power system is deregulating into Distributed Generation (DG) like Renewable Energy Sources (RES). This advancement helps in improving the environmental issues over fossil fuel-based generation. DG can be operated either as an islanding and/or as a grid-integrated power system. The uncertain nature of the grid at the Point of Common Coupling (PCC) has a significant impact on the stability of the DG grid-integrated Multilevel Inverter (MLI). The mathematical burden due to Park's transformation is reduced by utilizing stationary frame-based control techniques, and the delay due to PLL is avoided using PLL-less control. The proposed topology of MLI with asymmetrical configuration with input DC source ratio of 3:1 integrated with AC grid. This topology consists of the level generation and polarity generation units. The proposed MLI topology develops a nine-level output voltage by five switches per phase. This paper also presents the mathematical modeling of Voltage Modulated Direct Power Control (VM-DPC). The strategy for MLI under various dynamic conditions like load variations (
$P_{load}, Q_{load}$
), and different available power at PCC for DG interfaced MLI (
$P_{ref}, Q_{ref}$
) with AC microgrid is developed. A 15-kVA system is simulated in MATLAB/Simulink and tested under dynamic conditions to verify the design of the proposed system.