Analysis And Research On Photovotaic Grid-Connected Generation System

With the situation of energy resource crisis and the problem of circumstance pollution become more and more severity, exploitation and utilization the clean and regeneration energy resource is imperative. Solar energy is one of the most clean, practical and large scale regeneration energy resources. The whole world focuses on the use of Photovoltaic (PV). The PV grid-connected system will be the main utilization of solar energy,so it will be developed rapidly. Furthermore, with the development of high-performance Digital Signal Processor (DSP) chip,it is possible that some most advanced control strategies can be used to the PV grid-connected system. Under this background,the dissertation deeply researches the PV grid-connected inverter. It has significance to research on the PV grid-connected system.Solar array maximum power point tracking (MPPT) control and photovoltaic grid-connected inverter control are the two core part of PV grid connected system.Firstly, this paper introduces the operational principle and performance characteristic of PV cells, and describes the equivalent circuit and mathematical model dentally.Secondly, this paper introduces several traditional Maximum Power Point Tracking (MPPT) control algorithms. By comprising these control algorithms, the respective advantages and disadvantages have been found. Based on the maximum power of the fast track process and stability, an improved intermittent scan method is designed to achieve photovoltaic solar power generation system of the maximum power output and improve system performance and maximum power point tracking speed.Thirdly, this Paper focus on single-phase grid-connected system which can work on not only the Photovoltaic grid-connected system but also the Photovoltaic independent system,the control method of virtual value outer loop and instantaneous value inner loop,which can eliminate the static error, as well as make the output wave well. The structure and the calculate course of parameters of output filter for operation independently or grid-connected are given,and the design was testified by simulations and experiments.Subsequently, soft PLL was introduced in detail. The structure of Phase locked loop circuit and operating principle were researched. The experiment results testify that the output current of the inverter have the same phase with the gird,the efficiency of the inverter is1,this method is availability.Finally,TMS320LF2407A of TI incorporated is used as the main controller,a 1.5kW experimental prototype, the experimental waveforms of operation independent and grid-connected are obtained. It shows that the control strategy and the designed circuit can satisfy the design requests,this prototype works safely and stably.