Cooperative Interharmonics Control for Parallel Photovoltaic Inverters with Grouping Optimal Scheme

The interharmonics problem is generated by the application of perturbation and observation maximum power point tracking (P&O MPPT) algorithm, and it pose threats to power quality. When several PV inverters are connected in a parallel configuration, the power quality may be further exacerbated by the interaction between interharmonics. To address this issue, a cooperative interharmonics control with group optimization scheme is proposed in this paper. According to the sampling step size or sampling frequency of MPPT, the inverters are packeted by the group control. Then, for each inverter within its respective group, the appropriate phase shift angle is calculated by particle swarm optimization (PSO) intelligence algorithm, which is based on the functional relationship between the root-mean-square (RMS) value of total DC-link voltage perturbation and the phase angle of MPPT perturbation. After that, the MPPT phase-angel of each inverter is shifted based on the phase shift angle, and total DC-link voltage oscillation in each group can be effectively mitigated. With the proposed scheme, cooperative control of multiple parallel inverters is implemented and interharmonics can be effectively suppressed. And further, power quality can be improved. Simulation results are validated the effectiveness of the proposed scheme.