Optimal Deadbeat Control for Grid-connected Converter with LCL Filter

Active power filter (APF) now has become the most efficient and common apparatus to address the power quality problem. But its performance highly depends on its current-tracking ability, mainly the bandwidth of the control system. Based on this situation, this paper proposes an optimal deadbeat (ODB) control for the converter with an LCL filter. First, the reason why traditional DB control is unstable is revealed by analyzing the locations of poles and zeros of the LCL filter. And this issue is settled by offsetting the zero outside the unit-circle with a selected pole inside the unit-circle. Thus, through a purposive pole-placement approach, we achieve the widest bandwidth control method termed ODB control in this paper. Last, the corresponding grid voltage feedforward section which can cancel the influence of grid voltage on output and minimum-order state observer which is necessary with grid voltage feedforward applied is established. The well performance and the fast rapidity of the proposed control method have been testified by simulations.