Current Quality Control of the Three-Phase Grid-Connected Converter

Three-phase grid-connected converters are prone to poor grid adaptability and low grid side current quality issues. This article first proposes a unified voltage feedforward method based on phase advance correction based on the traditional dual loop control strategy, which effectively improves the grid adaptation ability under weak power grid conditions. By adding harmonic current control elements, the grid side current quality of the converter under weak power grid conditions is improved. In addition, for the application scenario of large capacity and small grid-connected inductors, L grid connection is changed to LC grid connection, and based on this, a control method based on reactive power compensation of parallel capacitors is proposed. Without changing the traditional dual loop control architecture, the reactive power of parallel capacitors is detected and compensated in real-time, effectively reducing the grid-connected current THD. A prototype of a 380V/50kW three-phase two-level grid-connected converter was built, and the effectiveness of the proposed algorithm was verified through experiments.