An accurate deadbeat control method for grid-tied converter using weighted average current sensing

To satisfy the requirement of operating DG units in both grid-tied and islanding microgrids, relatively large shunt capacitors are often selected for the output LCL filters of power converters. This modification can bring a few challenges, such as harmonic distortions and steady-state tracking errors, to the line current regulation during power converter grid-tied operation. In addition, the line current control problems can be more severe when the model-based one-step deadbeat current control scheme is used to reduce the computational load of DG unit controller and to enhance the dynamic current response. To overcome these limitations, a resonance dampened control method is developed utilizing the concept of the recently proposed weighted average current control with two current measurements. First, the weighted average current is accurately controlled via a modified deadbeat control scheme based on a virtual filter plant. To reduce the line current tracking errors caused by weighted average current approximation, a simple feed-forward term using existing grid voltage measurement is added to the line current reference of the proposed deadbeat control. Simulated and experimental results validate the effectiveness of the proposed method.