| Today,with the rapid development of economic globalization and industrialization,Energy crisis and environmental pollution are two important factors restricting sustainable development,The availability of fossil fuels in the near future will be exhausted,So looking for renewable energy instead of fossil energy is the trend of development,solar photovoltaic power generation to clean pollution-free,resource-rich,safe and reliable advantages of national sustainable development as an inevitable choice.In this paper,the SiC switch tube is applied to the photovoltaic grid-connected system,and the single-phase two-stage non-isolated photovoltaic grid-connected inverter is used as the research object.The DC/DC converter adopts the Boost converter circuit to realize the maximum power point tracking control,after the use of full-bridge inverter circuit to achieve grid control.Fistly,Based on the analysis of the principle of PV array power generation,the mathematical model of photovoltaic cell is mainly studied,and the principle of several commonly used maximum power point tracking is analyzed.On this basis,the small signal model of Boost is analyzed by using perturbation observation,the maximum power point tracking is based on the constant voltage method and the adaptive variable step perturbation observation method.The adaptive perturbation observation method and the fixed step perturbation are compared by simulation.Secondly,the control strategy of grid-locked phase is analyzed and the equivalent mathematical model is established according to the circuit topology.On this basis,the proportional-integral control for the current loop can’t eliminate the steady-state error and the repetitive control.The shortcomings of the slow current and the current loop are controlled by the compound control and the repetitive control and the robust control of the PI control in parallel.The simulation is carried out in Matlab/Simulink,and the PI control and repetitive control and robust control and repetitive control can significantly improve the THD injected into the grid current,suppress the low frequency harmonics of the system.Then,the design of the single-phase photovoltaic hardware system,and the calculation of the hardware parameters,including the switch tube selection,filter circuit,drive circuit,protection circuit,detection circuit,buffer circuit and other parameter design,based on TMS320F2812 designed for the control chip of the software system,including the main program,AD sampling procedures,grid frequency capture procedures,and network inverter procedures.Finally,the experimental prototype is built according to the theoretical calculation,and the feasibility of the hardware circuit and the control algorithm is verified.The test results show that the prototype is stable,safe and reliable,and has good performance. |
