Study On Matching Of Grid - Connected Control And Isolated Detection Method For Photovoltaic Power Generation

Energy shortage and the environmental problems brought by the consumption of traditional fossil fuel energies have become two major limited factors for the sustainable development of human society since the 21 st century. In consideration of the energy shortage and environmental problems, it is an irresistible trend to replace the traditional fossil fuel with the renewable clean energy. Photovoltaic power generation(PV) as the main form of the development and utilization of solar energy will become the main research task in new energy research.The adjustments of the consumption structure and the significant development of photovoltaic power generation technology enhance the rapid development of the grid-connected photovoltaic system. In this system the key units are grid control strategies and islanding testing. The time and power quality are different of the islanding testing if different grid connected strategies with different islanding testing methods are adopted. This paper conducts the matching test on the internal influence between the grid-connected controlling strategies and islanding testing methods through horizontal comparison. The matching result table will be given finally.This thesis firstly makes a research status of grid control strategies and gives an in-depth theoretical analysis of mathematical models of three grid control strategies, the double closed loop controlling strategy, hysteresis controlling strategy and the improved hysteresis controlling strategy. The simulation models of these three grid controlling strategies in the circumstance of Matlab/Simulink are also built to carry out the simulation analysis. The result shows the three grid–connected controlling strategies all meet the requirements of grid-connection under the same circumstance. It also shows that the content of the high frequency harmonics is high in the current of hysteresis controlling strategy with a higher distortion rate and the harmonic distortion rate of the double closed loop controlling strategy is the lowest in the three strategies. In addition, the relevant requirements of technical standards at home and abroad and the classification of the islanding detection are then introduced in detail and the principles of three islanding detection methods are been made specifically.Then the thesis focuses on setting up three kinds of grid-connection control strategies respectively with three island detection methods of matching simulation model to undertake simulation research. The simulation results concluded that it should not only use voltage detection as an island detection scheme, instead it should be combined with other test methods. In addition, the simulation result shows the matching tables and relevant conclusions about the grid control strategies and the islanding detection method.Finally, based on TMS320F2812, a grid-connected experimental platform is set up and the sampling and zero detection circuits have been improved to make a relatively ideal of the rising edge and low-going edge of the wave shape. Moreover, the hardware circuits and the system software such as the main circuit of inverter, control units, drive parts have been designed. Eventually, a simple analysis of the test results has been made that confirms the feasibility of the hardware circuits and the current closed-loop control design of the photovoltaic grid-connected inverter...