Performance & Analysis of Grid Connected Renewable Energy System with Multilevel NPC Inverter

Abstract: In recent years, multilevel inverters have gained popularity with medium and high power ratings. Renewable energy sources such as photovoltaic, wind, and fuel cells can be interfaced to a multilevel converter system. Wind is one of the most abundant renewable sources of energy in nature. Wind energy can be harnessed by a wind energy conversion system (WECS) composed of a wind turbine, an electric generator, a power electronic converter and the corresponding control system. The most advanced generator type is perhaps the permanent magnet synchronous generator (PMSG). The wind energy is connected to ac grid connected load. When the grid is concerned the loads may be unbalanced and non-linear in nature. Hence, grid should not inject harmonic and unbalanced currents into the grid. Harmonic currents and negative sequence currents (due to unbalance) will unnecessary increase the line currents. These problems are solved by using effective controllers with multilevel inverters. Multilevel inerter is used to step up the voltage and to reduce the THD. Here nine level and eleven level inverter are used and the voltage increases and THD reduces from 12.87 % to 4.38 %. Active and reactive power is controlled dc stabilization and the reactive power is near to unity. Here LC filter is used to remove the harmonics available in the system. In order to evaluate the performance of the proposed approach, a model of the AC grid, non-linear load, multilevel inverter and renewable energy resources (e.g., wind power generation) had developed in MATLAB / SMULINK environment.

Keywords: Wind Energy, PMSM, Total Harmonics Distortion, Multilevel Inverter.