A Novel Control Strategy for Three-phase Voltage Source Inverter Connected to the Grid via LCL Filter

摘要

LCL filter used in grid-connected inverter can suppress the output current harmonics around integral multiple switching frequency more effectively compared with the traditional L filter. However, LCL filter, a third-order system, may cause the control system unstable. In order to solve this problem, the system stability is qualitatively analyzed, based on this, a novel control strategy is proposed. In the strategy, a capacitor current closed-loop is added as an inner one, where the capacitor current feedback signal is calculated through estimation. With the proposed strategy, the high order harmonic components of the AC side current are suppressed effectively, at the same time the system stability is ensured. In the strategy, additional sensors are not of necessary, making equipment costs saved and system reliability improved. Effectiveness and feasibility of the proposed control strategy are verified by both the simulation and experiment results.