Interharmonics Suppression Scheme in PV System with Reference Phase Correction MPPT Algorithm

In general, the conventional perturbation and observation maximum power point tracking (P&O MPPT) algorithm has been widely used to ensure the maximum power output of photovoltaic (PV) arrays. When the maximum power point is found, the P&O MPPT method will generate a three-point oscillation at the maximum power point, which introduce interharmonics injection. And it can lead to a deterioration in power quality, and when multiple PV inverters are connected in parallel, the deterioration will be exacerbated. Especially, the most serious situation will occur when the MPPT of each battery in all parallel inverters is disturbed in phase, which caused large interharmonics in the grid. To address the above issues, a reference phase correction scheme for interharmonics control of PV systems was proposed in this paper. when the PV system operates stably at a maximum power point (MPP). The disturbance phase of its DC-link MPPT was calculated by one parallel unit, then sends it to another parallel unit. The shift phase required to offset the disturbance of the first parallel unit was calculated by the receiving parallel unit based on the received phase and its own MPPT disturbance phase. In addition, due to communication delays, a phase compensation method is adopted, which is compensating phase required was calculated by using delay measurements on the communication channel. The compensating phase and previously calculated shift phase are added, the final phase adjustment of the second parallel unit is determined. After phase adjustment, effective mitigation of equivalent total DC disturbances is reduced, and interharmonics injection was suppressed effectively. The effectiveness of the proposed control scheme was shown by simulation results.