Design Of Single-phase Grid-connected Photovoltaic Inverter

Energy conservation and environmental protection has become an importanttrend in the development of modern society because of the depletion of resources.Solar energy has lots of advantanges, such as abundant reserves, wide distribution,and the use of non-polluting, so has become the most potential renewable greenenergy.The main way of using solar energy is photovoltaic power generation. Atpresent, the photovoltaic inverter mainly has the following aspects. Because ofthe large volume and complex equipment, maintenance is not convenient. Theoutput current of grid-connected control system is instability. The conversionefficiency is low, and the cost is very high.Based on the above issues, a miniature grid-connected single-phasephotovoltaic inverter was designed in this paper. It was small in size, and couldbe integrated directly into the solar panel, so could be achieved for the maximumpower point tracking of each solar panel well. The inverter adopted a newtopological structure. It used two single-ended flyback converters for interleavingoperation. The photovoltaic control system could output stable current. It hadhigh efficiency, and cheap cost. The maintenance of system was convenient. Thesystem of the inverter is composed of the following parts: solar panels, flybackconverter, SCR phase, EMI filter and controller. Its basic principle as follows:DC voltage, output by solar panels components, was transformed into220V halfpositive sine wave by alternating flyback converter, and then entered the SCRphase converter to convert into sinusoidal voltage, filtered by a EMI filter, at lastincorporated into the grid. The DSP collected the voltage and phase of power grid,through the MPPT and PLL modulation, generated SPWM wave and drove thepower switch tube, so that the output current and voltage of inverter had the same frequency and phase with grid voltage. Besides power conversion circuit, theinverter also contained power supply of a small signal part, which was achievedby the auxiliary power module. The conversion of DC voltage is used linearregulartor IC.The hardware circuit principles of the system were designed, and the systemsoftware design ideas and implementation methods and key process areintroduced in this paper. Through MATLAB/Simulink, some experiment wassimulated. Finally some module circuit was tested simplely. It verified thecorrectness of the system design. Through the analysis of the simulation results,the work plan of the late prototype manufacturing was prospected.