Simplified Current Tracking Strategy for LCL-Based Rectifier under Unbalanced Grid Voltage Condition

Abstract

Unbalanced grid is a normal fault in power system, and in order to ensure the rectifier current tracking precision under this condition, the design and implementation of rectifier control strategies become more complex. In view of this, a simplified grid current tracking strategy is proposed, which is suitable for LCL-based rectifier operating in both balanced and unbalanced conditions. The grid current sinusoidal is achieved by tracking converter-side current of LCL filter. The current reference is only calculated by grid voltage and its 1/4 period lagging signal at stationary coordinates. Compared with conventional strategies, sequence separation and Phase-Locked Loop (PLL) are avoided. Besides, an improved active damping method is applied, which can accurately extract harmonic voltage and enhance the resonance suppressing effect. Simulation and experimental results verify the effectiveness of the proposed strategy.