Research On DC/DC/AC Converter Used For Photovoltaic Power Generation

At present,the energy consumption in economic and social development is still dominated by fossil energy,while the fossil fuels are non-renewable resources.The excessive use of fossil fuels will inevitably lead to the depletion of energy and cause serious damage to the ecological environment.Solar energy is a clean and environmentally friendly renewable energy,and the conversion of solar energy into electric energy for photovoltaic power generation is a main way to use the solar energy.Now,the photovoltaic grid-connected power generation system is the mainstream of photovoltaic power generation applications.Two key parts of grid-connected power generation are the high-boost topology of the pre-stage DC module of photovoltaic power generation and the grid-connected control system for post-stage grid-connected inverter,respectively.The two converters are mainly designed in this paper,and the main research as follows:How to expand the scope of photovoltaic cells work and improve the efficiency of power generation is one of the focus of research in this field.A high step-up ratio(gain)DC/DC converter is an effective way to solve the problem.Several circuit topologies commonly used in the pre-stage DC module of photovoltaic power generation system are compared and analyzed,in which the Floating-output Interleaved-input Boost-derived Converter(FIBC)has the advantages of simple circuit form,high output voltage gain and high system efficiency.The operation principle of FIBC converter topology is analyzed,and its small signal equivalent circuit model is established.Based on the FIBC mathematical model,the voltage and current double closed-loop control strategy is given,and the parameters of the regulator are designed.The mathematical model of LCL three-phase grid-connected inverter under different coordinate systems is established;The parameters of the LCL grid-connected filter are designed,which provides the basis for the selection of the filter parameters;The space vector SVPWM control strategy based on grid voltage orientation is adopted,and the required synthesized voltage vector is calculated according to the sector where the reference voltage vector is located;The double closed-loop control strategy of LCL grid-connected inverter in dq rotating coordinate system is given,and the parameters of PI regulation are set.To better control the grid current,a decoupling control is added to the double closed-loop control strategy.Based on Matlab/Simulink simulation software,the simulation models of traditional Boost and FIBC circuits are established.The stability and dynamic performances of the output voltages of the two circuit topologies are compared and analyzed under the same main circuit parameters.The simulation model of three-phase grid-connected inverter based on space vector closed-loop control strategy is established,and the simulation results verify the feasibility and stability of the proposed control strategy.