Nonlinear control of grid-connected PV systems using active power filter with three-phase three-level NPC inverter

Abstract

Grid-connected photovoltaic (PV) systems have become a significant area of interest for research scientists. Given this, this article presents a nonlinear control of grid-connected PV systems using active power filter (APF) with three-phase three-level neutral point clamped (NPC) inverter. The control objectives involve: (1) Forcing the PV output voltage to track a reference signal provided by the MPPT block in order to produce their maximum power, (2) Regulating the DC link voltage to satisfy a correct operation mode of the three-phase active power filter, and (3) Satisfying power factor correction (PFC) objective at the point of common coupling, PCC. Therefore, the suggested control strategy includes a cascade structure of two loops. The inner-loop regulator is designed using the sliding mode control technique and Lyapunov approaches to ensure the PFC objective by forcing the grid current to follow a given reference signal. The Outer-loop consists mainly of a proportional-integral (PI) regulator so that to regulate the output voltage. Further, the theory of instantaneous real power is used to calculate reference harmonics. The effectiveness of the proposed controller is demonstrated through simulation results using MATLAB/Simulink.