Model-based controller for current injection with a single phase NPC inverter

This paper presents the modeling and controller design for a neutral point clamped multilevel converter (NPC) which is used to inject power into the grid. The current injection to the grid is motivated by two main goals. One of them consists in using the inverter to provide power to the network; in this case the energy is taken from an external source and is supplied to the mains. On the other hand, the inverter can also be used for the harmonic compensation of currents caused by nonlinear loads. The proposed controller is designed to inject a sinusoidal current into the grid using an external DC voltage source. And also the converter in the presence of a nonlinear load in a common connection point behaves as an active power filter to compensate harmonic distortion in the current. The selected topology is connected to the mains through an L filter. In order to assess the performance of the proposed controller, simulation results are presented for an NPC converter connected on a common connection point with a nonlinear load.