Research On The Control Methods Of Photovoltaic Power Generation System

As the world energy crisis, the development of new energy has become more and more urgent. PV as a kind of clean energy, its development has been accepted the world's attention. In this paper, the various structural modules in solar power system(including the solar array, DC chopper circuit, battery energy storage unit and inverter) as the research object, based on the topological structure of each module and the actual nature of the work, the control methods of each module in photovoltaic power generation system are investigated.Modules of photovoltaic power generation system, including the solar array, DC-DC chopper converter,battery energy storage unit and the inverter.The topological structure and working principle of the control method are discussed. MPPT control is the bridge connecting the circuit and the inverter circuit, study about the working principle of disturbance observation method and incremental conductance method in-depth are made. The simulation model is built, and a brief analysis of its working process are made, which lay the foundation for the research of inverter connected grid.Inverter's main task is to complete the conversion of DC and AC in the photovoltaic power generation system. According to the inverter topology, the mathematical model is established.Putting forward a kind of droop control method, based on the principle of PV power output active power and voltage amplitude,reactive power and frequency are linear relationship, to adjust droop coefficient.Using matlab/Simulink to build a simulation model,the results show that the droop control method can maintain voltage and frequency steady of system under the condition of on-grid and off-grid process, as output voltage and current waveforms of system is in good condition.By introducing the concept of photovoltaic DC microgrid, the component and structure of microgrid operation characteristics aboutDC and AC microgrid are compared.Summarizing the application of hierarchical control method in the microgrid. Based on photovoltaic DC micro-grid, this paper aimed at the DC micro-grid voltage stabilityproblem, proposed a hierarchical coordination control method of DC bus voltage. The method was based on the control of DC bus voltage variation to coordinate photovoltaic battery energy storage interface, netside interface and the interface work by setting resonable threshold voltage, ensured that under different conditions can keep the network in active power balance. During the on-grid and off-grid process, switching between layers for a smooth design to reduce the transient current impaction. Used Matlab/Simulink simulation and experimental verification, the results verify the effectiveness and feasibility of the method.