A Control Method for Suppressing Midpoint Potential Fluctuation of Three-level Grid-connected Inverter

Abstract

The invention discloses a control method for restraining point potential fluctuation in a three-level grid-connected inverter. The control method comprises the steps that firstly, signals of direct-current bus voltage are extracted from the two ends of a direct-current bus capacitor and the estimation value of point potential fluctuation in the direct-current bus capacitor is determined, wherein the signals of the direct-current bus voltage comprise the tracking value of the direct-current bus voltage and first-order and second-order differential signals; a nonlinear PI controller is used for controlling the difference between the reference value of the direct-current bus voltage and the actual value of the direct-current bus voltage; the estimation value of point potential fluctuation in the direct-current bus capacitor is used for compensating point potential fluctuation in the direct-current bus capacitor of the inverter to obtain the actual controlled quantity of the inverter. The control method lowers the unbalanced degree of point potentials in the direct-current capacitor of the three-level grid-connected inverter, reduces harmonic distortion of currents output by the inverter, improves the quality of electric energy output by the inverter; reduces voltage borne by an inverter switch device and prolongs the service life of the inverter switch device and the service life of a voltage-dividing capacitor; the robustness of a system is improved and negative influences on the system from non-measureable disturbance are resisted.

Description

technical field [0001] The invention relates to an inverter control method, in particular to a control method for suppressing midpoint potential fluctuations of a three-level grid-connected inverter. Background technique [0002] New energy grid-connected power generation has played an important role in alleviating energy shortages, improving the living environment, and ensuring sustainable social development. As the core equipment in the new energy grid-connected power generation system, the inverter's control performance directly determines the power supply reliability and power quality of the grid-connected system. Among all grid-connected inverter topologies, the diode-clamped three-level grid-connected inverter is a converter that has developed rapidly in recent years, and has the advantages of high operating efficiency, small voltage change rate and low harmonic content. , It has been widely used in new energy grid-connected power generation, active power filter and o...

AI Technical Summary

Problems solved by technology

[0004] The existing midpoint potential balance method mainly realizes the suppression of midpoint potential fluctuations by improving the inverter space vector modulation strategy, which belongs to the indirect control method and fails to realize the direct compensation of midpoint potential fluctuations.

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