A Decoupled Hybrid Current Control for Improving the Performance of 60° DPWM-Based Three-Phase Grid-Connected Inverter

Nonlinear boundary control technique can offer superior dynamic behavior and eliminate the LCL-filter resonance in the grid-connected inverter. However, the chattering might be aroused by the distorted intracycle voltage information in the control law. It becomes worse when the nonlinear boundary controller is directly applied in three-phase three-wire inverter configuration. A hybrid current control scheme utilizing the decoupled predictive hysteresis capacitor current controller integrated with the linear grid current controller is proposed in the paper. By applying the 60° discontinuous pulse-width modulation scheme and using the virtual dual-buck decoupled structure, two separate sets of switching criteria for dictating the switching states of two specific half-bridge legs are formulated to avoid the interactions amongst phases. A small-signal ac model is also built to study the transfer characteristics of such hybrid current controlled inverter system. Simulation and experimental results have been offered to evaluate the effectiveness of the proposed method. Both results meet the theoretical predictions.