Research On Single-phase Photovoltaic Grid-connected System

Nowadays, Photovoltaic(PV) grid-connected generating technology becomes a very important research area in the field of new energy power generation. This paper focuses on the household-type single-phase photovoltaic grid-connected system and does a lot of research which involves maximum power point tracking (MPPT) methods for PV arrays, grid-connected control of two-stage PV system, filter of grid-connected system, non-islanding protection. Based on the Theory and Simulation Analysis of this system, a prototype was designed.Firstly, the simulation model of PV arrays is established, which is used to simulate its electrical performance. And this simulation model can work at maximum power point quickly and accurately under the control of incremental conductance method in Boost circuit.Secondly, the DC/AC stage adopts the scheme of two-loop voltage and current control, makes unity power factor grid-connected operation realized. The LCL filter reduces the harmonics interference of current efficiently, and the Total Harmonic Distortion(THD)can meet the request of power system. Then, coordinated control system of two-stage makes the whole system work reliably. The power of PV arrays can be the maximum by MPPT based on Boost circuit, and the DC/AC circuit feeds the power into the electricity grid system. The whole system is modeled by Matlab, and the active frequency drift method is used to this simulation system. Simulation results show that the whole system can not only realize a lower THD and unity power factor grid-connected operation with the maximum power of PV arrays, but also can prevent Islanding effect from taking place. Besides, the system shows satisfactory dynamic and stationary performances.Finally,the hardware system which involves switched power supply,Main Circuit and controlled circuit is designed as a prototype. Associated with the software system which is based on the main control chip dsPIC30F2010, the prototype can realize some fundamental functions of the system, and the results show correctness and feasibility of this scheme.