A New Control Strategy with Simplified Model and Kalman Filter Estimator for Grid-Tied Inverter with Asymmetric LCL Filter

In grid-connected inverter systems, the three-phase asymmetric LCL (A-LCL) filter has outstanding characteristics of simple structure, almost the smallest total inductance, and the strong resistance to the adverse effects of parameter shifts. Nevertheless, the order of this kind of power filter is high, and the control model is complicated due to its asymmetric structure. In this paper, a simplified modeling method, which effectively reduces the system order is proposed, without affecting the control performance. Then, the Kalman filter estimation (KF-estimation) is adopted to reconstruct the PCC voltage. A 380 V/50 Hz/6 kW three-phase laboratory setup has been developed to verify the correctness and effectiveness of the proposed control strategy.