Research On Single-Phase PV Grid-Connected Inverter And Its Low Voltage Ride Through Control Strategy

With the extensive use of fossil fuels caused by energy crisis and environmental pollution is becoming increasingly serious,resulting in "haze" "PM2.5" and other hot words are well known,development and utilization of renewable energy is imminent.Solar photovoltaic grid-connected power generation with its rich resources,clean and pollution-free,can be combined with the advantages of building resources to make it a good development prospects and cause more and more extensive attention.The single-phase single-stage photovoltaic grid-connected power generation system in the form of photovoltaic roof is considered to be the main use way of small and medium-power photovoltaic grid-connected power generation technology because of its simple structure,flexible configuration,low cost,safe and reliable.With the increase in the proportion and permeability of the system in grid applications,the system's low voltage crossing capability should also be available.In this paper,the single-phase single-stage photovoltaic grid-connected system is used to deal with the control strategy of low voltage fault in power grid and the key technologies such as maximum power point tracking and phase-locked loop of the grid-connected system are studied and improved to realize single-phase photovoltaic system can be stable operation of the overall control in the case of normal and low voltage faults?In this article,the mathematical modeling and analysis of photovoltaic cells and inverter topology are carried out that based on the working principle of photovoltaic power generation system at first?Then,through comparative analysis the advantages and disadvantages of the traditional MPPT method in PV cells,in view of its misunderstanding phenomenon,this paper proposes an MPPT algorithm based on extreme search,next,the phase-locked loop technology in the process of grid connection is researched.After comparative analysis of a variety of different types of phase-locked loop's performance In the case of grid voltage normal and drop failure,a single phase system phase-locked loop based on SOGI is proposed for single-phase single-stage photovoltaic grid-connected system?finally,according to the technical requirements of photovoltaic grid-connected low voltage crossing,a LVRT strategy based on single phase dq current decoupling control is proposed?The strategy can adjust the grid of active current and reactive current reference through the algorithm based on the grid voltage real-time drop depth,that can let the PV grid-connected inverter inject a certain amount of reactive power into the grid to help the grid to recover the voltage,so that can achieve LVRT.In addition,we also carried out the hardware circuit and software flow design that based on the above theory and simulation results.Finally,all the improved application of the above technology through the simulation software MATLAB and experimental platform to verify their correctness and effectiveness.