Control Strategy for Single-Phase Grid-Interfaced Modified Multilevel Inverter Topology for Distributed Power Generation

In this article, a multiresonant proportional-resonant (PR) controller-based current controller is presented for a single-phase multilevel inverter topology, enabling grid-current injection into the distribution grid at unity power factor. The multiresonant PR-controller compensates third and fifth harmonic components to improve the harmonic spectrum of the grid injected current. Moreover, to reduce the switching losses in the power electronics converter, the nearest level modulation technique has been adopted, increasing overall efficiency. Furthermore, a modified multilevel inverter has been presented for grid integration, which requires a reduced number of switching components and isolated dc sources. In addition, system stability and sensitivity analysis are presented to evaluate the performance of the controller. The proposed scheme reduces the harmonic content in the grid current and the steady-state error in the grid injected power. Furthermore, the multiresonant PR-controller and PI-controller performance is verified in terms of steady-state error and total harmonic distortion in the grid current. An experimental prototype of the 21-level modified multilevel inverter-based grid-connected system has been developed to validate the claim.