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