Research On DC/DC Converter In Photovoltaic System

The solar energy is one kind of green and renewable energy source which has the advantages of big reserve, low cost, and do not pollute the environment.Therefore, the use of solar energy is attracting more and more people's attentions,and the solar photovoltaic technology is generally the focus of attention.In recent years, along with the completion of many domestic polycrystalline silicon production projects one after another, our country will soon realize self-sufficiency in the material of photovoltaic cells, the era of promoting large-scale grid-connected PV system is just around the corner.However, there are no specific research for the grid-connected photovoltaic system which conforms to China's national conditions and has the potential to promote,and research its technical features. At present, the application of the photovoltaic system is still based on independent ones and grid-connected system is still in its infancy.In addition,there are weaknesses of Instability in the running , low reliability and lacks of protective measures in domestic photovoltaic system and the problem of building with construction is not considered. With the above background, we have carried out a number of studies on the subject of Photovoltaic power generation technology.By analyzing the characteristics of several kinds of grid-connected PV system and the development of grid-connected PV system in recent years, the paper discusses the grid-connected photovoltaic system which conforms to China's national conditions and has the potential to promote,and research its technical features.The output characteristics of the solar cell are affected by environmental factors such as light, temperature. In order to track the maximum power point of the solar cells to increase the utilization of them,the DC/DC converters which are controlled by maximum power point tracking algorithm are needed in these Photovoltaic systems.The paper focuses on the DC/DC converter which is used to the small or medium sized multi-string two-stage grid-connected PV system. powersmall and medium-sized power of multi-slip, two-stage photovoltaic grid-DC converter system.On the basis of introducing the solar power generation principle, the paper discusses the necessity and the principle of achieving maximum power point tracking with DC/DC converter.After introducing and analyzing the current maximum power tracking algorithm, we research two typical of algorithms, P&O and INC with MATLAB and propose a variable step Conductance Increment method to improve the performance of maximum power point tracking. In order to verify the performance of the algorithm proposed in this paper,we build the experimental platform on the basis of the overall structure simulation.The mainly work in hardware include main circuit designing of the DC/DC converter, drive circuit designing of the MOSFET,designing of the isolated power source, designing of start buffer circuit as well as the designing of the signal sampling circuit.The mainly work of the software part is compilying control program which is based on TMS320F2812 industry specific control 32-bit fixed-point DSP using the on-chip resources of DSP, the software part includes the program of the maximum power tracking algorithm,, the AD signal sampling program, the PWM pulse trigger module program, fault diagnosis procedures, as well as the anti-jamming design for the entire time the program is running. Based on the above work,testing and trial work is involved. The experimental results illustrate that the hardware and software design is feasible and satisfactory.In this paper,the work of system design, simulation , hardware and software and software design laids the foundation for the building of the new grid-connected photovoltaic system and provides a reference and guide for the follow-up work.