Design of Single Phase Grid-connected Photovoltaic Power Plant based on String Inverters

Based on the design of string inverters, a high performance gird-connected photovoltaic (PV) power plant is presented. The plant consists of grid-connected single phase inverters, intelligent cluster controllers (ICC) and user-friendly monitoring software. The feedforward control strategy based on grid voltage and load current is proposed to improve inverter's dynamic response. With an optimal maximum power point tracking (MPPT) algorithm, the maximum power output of PV modules is achieved by using forth-back voltage increment perturbation. A Sandia frequency shift based strategy which increases the anti-islanding ability of grid-connected PV power system is also discussed. The proposed system can simultaneously monitor all the inverters on-site of PV modules. The verification has been made on the experimental units. The results show that the plant has excellent capability of high efficiency, intelligent maintenance and integrated management