Research On Off-grid Photovoltaic Power Generation System

With the development of society, coal, petroleum, natural gas and other fossil energyshortage and environmental problems caused by the use of fossil energy have becomeincreasingly prominent, and developing less pollution, renewable energy has become theconsensus of the world. In all of the new energy resources, solar energy is more favored bygovernments, because the solar energy has the advantages of clean and widely distributed.But the cost is too high is the biggest obstacle to the development of solar energy, and througheffective control to improve the utilization of solar energy has been an important task in thefield of solar power to reduce the cost of photovoltaic power generation. About thisproblem, this paper conducted in-depth study of off-grid photovoltaic power generationsystem.Photovoltaic power generation system is designed in this paper useing DC/DC andDC/AC two level inverter. The DC/DC uses boost circuit to complete photovoltaic maximumpower point tracking (MPPT),and the DC/AC part based on SPWM double closed loopcontrol theory to realize the inverse function.First of all, established simulation model of photovoltaic cells, On the basis ofanalysis of photovoltaic cell output characteristic curve and the misjudgment and oscillationproblems of fixed step disturbance observer method, an improved maximum power pointtracking (MPPT) control method is proposed. And then build the simulation model in theMatlab/Simulink environment to verify the improved method.Then, analyzes the modulation method of SPWM, established the mathematical model ofsingle-phase full-bridge inverter circuit and analysis. In-depth analysis of the double closedloop control strategy of inverter voltage outer loop current loop, voltage in the design loopwith PI regulator, current inner loop P regulator, and the parameters of the double closed loopcontrol system are set by pole placement method.Finally, based on the theory study and simulation, using TI’s TMS320F2812as the controlchip, the power from the hardware and software system of photovoltaic power generation system is designed. Combined with laboratory conditions to build an experimental platform,from the test results can be seen in the experimental circuit, the circuit design to realize thefunction of each part, validate the rationality of design.