An Interharmonic Suppression Control Scheme in PV System Based on DC-Link Voltage Perturbation Reduction

The perturbation and observation (P&O) maximum power point tracking (MPPT) algorithm has been widely used in PV system. However, the dc-link voltage perturbation and drift problem during the tracking process is the main reason of interharmonics injection in PV system. In this paper an interharmonics suppression control scheme based on dc-link voltage perturbation reduction was proposed. To effectively suppress the interharmonics injection. The interharmonics suppression control scheme was divided into two stages according to the insolation change. When the insolation was stable, the dc-link voltage reference value was taken as the input variable. When the characteristic of three points oscillation was met for three consecutive times, it indicates that the MPP has been found. The perturbation step size was set to 0 and operated stably at the MPP. When the insolation changed, the power and voltages of three continuous operating points were sampled and used to ensure the correct tracking direction, which could reduce the dc-link voltage perturbation. The proposed control scheme could effectively reduce the perturbation of dc-link voltage and interharmonics injection. Simulations have been carried out to verify the effectiveness of the proposed control scheme in interharmonics suppression.