A Study on Current Balancing of Three-Phase Inverters with Direct Power Control Under Unbalanced and Harmonic Distortion

Abstract

This paper investigates voltage regulated balanced sinusoidal grid current control under unbalanced and distorted grid conditions, where double-frequency power and harmonic oscillations. To avoid instability, delay, and computational complexity associated with PLL-based synchronization, a PLL-less Grid Voltage Modulated Direct Power Control (GVM-DPC) strategy is proposed. A parallel Dual Second-Order Generalized Integrator (DSOGI) is employed for fast and accurate sequence extraction in the stationary frame. The experimental study includes: 1) performance of traditional modulation, and 2) performance of the demodulation strategies using different. Results demonstrate that both proposed methods outperform the traditional approach. The combination of positive-sequence voltage modulation with nominal voltage demodulation achieves a Current Unbalance Factor (CUF) of 0.05% and reduces the grid current Total Harmonic Distortion (THD) to below 3% without additional harmonic compensation, complying with IEEE 1547 standards.