Research On MPPT And Anti-island Protection Of Photovoltaic Gird-connected System

Photovoltaic power generation has become the focus of the development of new energyin the world, and photovoltaic grid-connected system is the main development trend,thispaper makes deep analysis and research to maximum power point tracking(MPPT) andislanding detection.First, With analysis of principle and drawbacks of traditional MPPT algorithm, this papergives a novel MPPT algorithm based on the centered differentiation, builds the MATLABmodel and gets a good simulation result. Evaluations have successfully illustrated theeffectiveness of the proposed algorithm,which is not only improve the precision of maximumpower point(MPP) but also have good effect to reduce the oscillation.Second, frequency or phase shift methods which inject harmonic into grid is ineffectivewhen phase match between the output of inverter and the load. An anti-islanding methodusing reactive power control is gived.The method has few harmonic components compared tothe conventional methods. The results of simulations show that the inverter requires a veryshort time to detect the islanding and to stop the PV system.Finally, based on detailed analysis and summary of grid system, a laboratory3KWgrid-connected PV installations is designed. TMS320LF2812considers as the control centerof grid-connected system to achieve maximum power point tracking, grid connected invertercontrol, communication and display, etc.Through experimental analysis, the total currentharmonic distortion (THD) of grid-connected inverter output waveform was less than3%;Power factor was greater than0.99, and the system efficiency was up to95%, the desiredspecifications were achieved. Experimental results show the effectiveness of the design.