Control strategy study for three phase photovoltaic grid-connected inverters

In the application of three phase photovoltaic gird-connected inverters, how to meliorate quality of grid current is an key issue concerned. Adopting LCL filter to connect inverters with grid brings about a good filtering effect, but it makes control complex. Considering existing control method, in this paper, a strategy that cascaded proportion integrity (PI) and proportion resonation (PR) with grid voltage feed forward based on dq synchronous rotate frame is proposed. The model of three phase inverter is founded and controller was analyzed and derived. This strategy meliorated the dynamic characteristics of connecting grid by feed forward, achieved zero error tracking using PI, and suppressed harmonics currents effectively via PR. Last, simulation and experiment on a 100 kW PV array grid-connected inverter are done. The results show that this proposed strategy achieves smooth grid current starting and fewer harmonics current.