A Model Predictive Current Control Method Based on npc Topology Grid-connected Inverter under Unsymmetrical Voltage

Abstract

The invention relates to a model predictive current control method based on an NPC topology grid-connected inverter under asymmetric voltage, and introduces the model predictive current control technology into the control of the NPC grid-connected inverter. In the case of asymmetrical faults in the power system, in order to accurately track the positive sequence voltage phase angle of the system, the decoupled double synchronous reference frame phase-locked loop (DDSRF‑PLL) phase-locking technology is introduced to track the positive sequence voltage phase angle; on this basis In the above, using the positive and negative sequence components of the fundamental frequency voltage obtained after DDSRF‑PLL decoupling, combined with the instantaneous power theory, realizes the model predictive current control that suppresses the negative sequence current component, active power and reactive power oscillation as the control target; in the control process In , in order to ensure the balance of the capacitor voltage on the DC side of the NPC grid-connected inverter, a weight coefficient term is added to the cost function. The entire control process of the invention reduces the use of PI controllers, enhances the response speed of the system, and makes the grid-side end of the grid-connected inverter have higher power quality and stability.

Description

technical field [0001] The invention relates to the field of grid-connected inverter control, in particular to a model predictive current control method for a three-phase grid-connected inverter based on NPC topology under asymmetrical voltage. Background technique [0002] Looking at the research hotspots of new energy power generation systems in recent years and the research status at home and abroad, wind power, photovoltaic power generation and other renewable new energy power generation technologies have achieved unprecedented development. The new energy power generation system is a network dominated by inverters, so the development of new energy also drives the rapid development of power electronic converter technology. When the grid system is in a stable operating state or a three-phase symmetrical fault occurs, the traditional proportional-integral (PI) control strategy based on the positive sequence synchronous coordinate system can achieve a good control effect; bu...

AI Technical Summary

Problems solved by technology

The occurrence of this type of asymmetric fault, the access of high-power single-phase loads, the unbalanced distribution of single-phase loads in the three-phase system, and the randomness of power consumption of single-phase loads will cause the three-phase voltage imbalance of the power grid.

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