Research On The Droop Control Strategy Of PV Micro-grid Based On Line Impedance Matching

With the excessive consumption of conventional energy,environmental pollution problems have become increasingly prominent.In order to alleviate the problem of environmental pollution,renewable energy power generation system emerges.These micro network systems have become a focus of research,which are composed of distributed power supply,energy storage,local load and control protection device.The three-phase voltage source inverter system is selected as the research object in this thesis,the circulation problem of parallel inverter and the power equalizer of parallel inverter are studied.Therefore,the adaptive droop control method is presented,which is applied for the high and low voltage microgrid.Firstly,the system consisted of photovoltaic cells and the maximum power point tracking is adopt to supply for three-phase voltage source inverter in the DC power inverter system.The PV mathematical model and the battery mathematical model are established and simulated in this thesis.The traditional perturbation and observation method of maximum power point tracking algorithm based on making the maximum power point of the photovoltaic battery output principle is researched.A fast and stable maximum power point tracking algorithm is proposed in this thesis,which is verified by the simulation.The mathematical model in the three-phase stationary coordinate system and two-phase rotating coordinate system of the three-phase voltage source inverter is deduced.The specific parameters of the LC filter based on filter topology and filtering characteristics are designed.The influence of power line impedance on power distribution is studied,and the properties of traditional reverse droop control and traditional droop control is analyst in detail.the design of the power controller and the voltage and current double loop controller is carried out for the analysis of the droop method.Because of the existence of the line impedance difference between actual high and low voltage microgrid system,which leads to the circulation problem and power sharing between parallel inverters.Therefore,the relationship between traditional droop coefficient,active power,reactive power and power line impedance of power distribution are researched in this thesis.Hybrid droop control method of dynamic regulation droop coefficient is proposed,and the parameters selection of the improved droop control is analyzed and verified.Finally,according to the adaptive hybrid droop control method improved,a high and low voltage microgrid simulation model based on different impedance characteristics is established.The sudden increase of load and load sudden decrease example is simulated,and in the same example and the traditional droop control strategy were compared.Whether electric power lines are resistive or perceptual(i.e.whether it is high or low voltage microgrid)is improved,and the improved control algorithm can obtain good effect of the inverter power sharing,and minimize system circulation.