Research & Design On Grid-connected Photovoltaic Generation System

With the development of energy sources exhausted and environmental polluted seriously, Photovoltaic generation system has become the development focus and every country pay more attention to it for it's characteristics in nowadays.Because grid-connected photovoltaic power generation system is the development trend of photovoltaic utilization, So Single-Phase Grid-connected Photovoltaic generation System was studied in this paper and 1.5KW Single-Phase Grid-connected Photovoltaic generation device was designed.Based on the detailed analysis of the main circuit topology, MPPT, anti-islanding and the conversion control, a kind of non-isolated main circuit topology which adopts dual BOOST to match of voltage in pre-stage and full bridge inverter in last stage was chosed in this paper, which has many advantages such as easily controlling DC/DC conversion in pre-stage, small fluctuation in middle DC bus voltage, high efficiency, small volume and so on. MPPT is achieved by adopting a way of last stage; both passive and active ways were adopted in anti-islanding. Conversion control on grid-connection which is the most important link in grid-connected photovoltaic power system is to transform pre-stage DC to AC with the same frequency and phase. Besides it also keeps output current being unit power factor and total harmonic distortion being less than 5 percent. On the basis of comparison of all kinds of inverter grid-connection control strategies, instantaneous current control with grid voltage feed-forward compensation was adopted and achieved at last.UC3875 and TMS320LF2812 is the control core of the whole system. The pre-stage dc-bus voltage is in dual-loop controlled by uc3875, meanwhile, MPPT, anti-islanding, converter on grid-connection, communication parallels and fault protection were realized by TMS320LF2812 in the last stage. The general working in this paper includes: detailed theoretical analyses, main circuit design, software & hardware circuit design, debugging and experimental waveforms analysis, and so on.