An improved DC-link control for dual-stage grid connected Photovoltaic system using three-level Neutral Point Climped inverter

In this paper, we provide two options for the intention of new control strategies. The first is novel adaptive DC-link voltage control approach based on the feedforward and PI regulator (FF-PI). The second is a finite control set model predictive current control (FCS-MPC). We address the problem of switching power losses, the harmonic current and voltage balancing problems wich consequently degraded power quality and negatively affected the power factor. This paper proposes two robust control strategies for reducing this drawback. In these strategies, the DC-link voltage is regulated by a hybrid control technique combining a PV feedforward term and a standard PI controller DC link voltage error, which have been proposed by setting DC-link voltage reference according to CPI (common point of interconnection) voltage for control of grid tied voltage source converter. In addition, the natural voltage balancing capability of the three-level and three-phase neutral-point-clamped (NPC) using the predictive control (FCS-MPC) to generate pulse with modulation (PWM)signal for the inverter. The unit vectors are estimated from grid voltages to synchronize output currents of the voltage source using a phased looked loop (PPL). Finally, Several Matlab simulation results have verified the operational performance of the proposed control strategies. In this paper, we argue that the total harmonic distortion THD of grid current has been found well under the limit of an IEEE standard, improving power quality and good disturbance rejection after sudden changes of the active power.