Single-phase Grid-connected Photovoltaic Power Generation System

As a new type of green renewable energy, solar energy has advantages of large reserves, clean and environmental. With the energy crisis and the environmental pollution intensifying, more and more attention has been paid on the use of solar energy; the most important technology about the use of solar energy is photovoltaic (PV) power generation. Recently, two to three decades of development shows that the gird-connected PV power generation is the mainstream of solar photovoltaic technology, in which grid-connected inverter of PV system becomes the core energy conversion device. It mainly depends on power generation efficiency and cost of PV system whether the market would accept the PV grid-connected inverter or not. These two factors will decide to whether PV power generation system can be used on a large scale. However, the choice of circuit topology and the maximum power point tracking (MPPT) technology are closely related to these two factors, so at present, the development of high efficiency and high cost-effective PV power generation system is a world goal.This paper analyzes some common circuit topology in current grid-connected PV system, and on the basis of summarizing the advantages and disadvantages of these topologies, a non-isolated two-stage high-frequency circuit topology is chosen as the main circuit, with which a single-phase grid-connected PV system is implemented. In this system, Boost converter is adopoted as front-end circuit and Full-bridge inverter as the back-end circuit then chosen to inplement grid-connected power generation. As to the Boost converter here, not only raises the PV voltage to the desired DC-bus voltage, but also achives the MPPT. The operation principle is dicussed, and the control strategy analysed as well, especially the fuzzy controller for implementing MPPT is designed in detail.In this paper, the modeling and simulation of the two-stage PV power generation system is implemented with MATLAB. And1.5KW enperinmental prototype is designed based on TMS320F2808which is from TI. The simulation and the experimental results show that the proposed fuzzy controller can accomplish the MPPT and ensures the PV to generate the maximum power. Because of that the digital control is applied to the system, the design cost is much lower and the system easier to be maintained, besides, the high reliable performance is gotten.