Multi-step finite control set model predictive control of photovoltaic three-level NPC inverter with harmonic governance

Abstract

To solve the problems of complex control structure, too many parameters to be tuned and complicated modulation module design in the traditional dual closed-loop control strategy of neutral point clamped (NPC) three-level PV inverter. A control strategy is proposed for NPC three-level PV inverters based on multi-step-ahead finite control set model predictive control (FCS-MPC). Based on the derivation of the mathematical model of the PV inverter, the current predictive control of the PV inverter in the αβ frame is realized based on the basic principle of FCS-MPC, which effectively reduces the control parameters of the PV inverter. Additionally, based on the inherent advantages of FCS-MPC, the mid-point potential balance of the DC side, reducing switching frequency and harmonic are simultaneously realized by setting the appropriate objective function. Furthermore, the accuracy of the prediction is further improved by the use of multi-step-ahead predictive control. For the harmonics problem during the fault ride-through of the conventional PV inverter, the causes of harmonic generation are revealed and a notch filter is designed to reduce the harmonics generated by the PV inverter during the low voltage ride through (LVRT). Finally, the time domain simulation software is used to verify the effectiveness and feasibility of the control strategy in this paper.