Modified grid-connected current source inverter for multi-string PV system

In this paper, the principle of a power conditioning unit for multistring PV power generation system is proposed. The proposed power conditioner is based on the current source inverter (CSI) topology. All PV strings are connected in parallel to a DC bus through the modified wave-shaping circuits. The instantaneous current at a DC bus can be obtained by summing the output DC current of each wave-shaping circuit. To achieve the unity power factor at the utility grid, the DC link current can be controlled with the sinusoidal PWM scheme. The AC output current can be achieved by unfolding the PWM current at a DC bus. The details of the operating principles and the system configurations of the proposed system are described and verified by the simulation results.