Design And Optimization Of Droop Controller In Photovoltaic Microgrid

Due to the rapid development of industrialization around the world,the demand for energy is growing,the reserves of non-renewable energy are getting less and less,and the energy and environmental problems are becoming more and more serious.And solar energy as the clean energy in new energy,because of the unique advantages has become new energy development inemerging research hot spots.With the deepening of photovoltaic power generation study,PV systems and network are gradually common,and the drawbacks of the network caused by the operation are more obvious.Micro-grid is a small network which usually use the new renewable energy as a power generation mode of distributed power.PV is widely used in microgrids and research theory and engineering practice is relatively perfect clean energy.Control micro-grid of the core technology is reflected in the control inverter,the inverter is the core device that relays the microgrid to maintain reliable operation,so the focus of this paper on the control of photovoltaic micro-network inverter.There are three control strategies for microgrid inverter:droop control,constant voltage constant frequency control and constant power control.The most common method used today is drooping control.The droop control utilizes the sagging characteristics of the synchronous generator when it is running,so that it has a certain frequency modulation performance when the microgrid is running.However,the FM is similar to the primary frequency of the power system,can't achieve the worst frequency modulation.In the micro-grid operation,the use of drooping control will cause obvious drawbacks.When the system load is disturbed,the frequency fluctuates greatly and rapidly,and Low-frequency load shedding equipment may not have enough time to action to eliminate the disturbance,hinder the power grid to maintain a stable state.This paper first discusses the research background of thesis and then discusses the definition and characteristics of micro-grid,as well as the of the current study,discusses the status of various control methods.From the characteristics of photovoltaic cells and the maximum power tracking point,its tracking method is described in detail,building a model of photovoltaic cells is simulation analysis in MATLAB.There is detailed analysis micro-network inverter power control method and multi-microsource system work control method.Secondly,on the basis of the principle of the droop controller,the droop controller is designed,which usually includes the power controller,the voltage and current double loop controller,the filter,the droop control link and the reference voltage synthesis.The parameters of each part of the controller are set up by theoretical calculation.The effectiveness and feasibility of the droop control model are proved by simulation operation,but the shortcomings of droop control are also revealed.In the Matlab/Simulink,a small-scale PV microgrid model is established.The peer-to-peer control strategy is adopted in the system.The droop control strategy is used in inverter power to analyze the operating characteristics of the microgrid and the microgrid performance when the load changes.Then,in the droop controller P-f control link to join the virtual impedance to optimize the droop control method,introduce integral calculation in reactive power calculation,make up for the lack of the traditional drooping control method:When the system load has a certain disturbance,the frequency can be more gentle close to the steady-state value,so as to get enough time for low-frequency load shedding equipment load,so that the system can maintain a stable operation time;The power distribution of each power supply is analyzed,and the system can calculate the power distribution according to the micro-source capacity.Finally,build a single inverter power supply,analog photovoltaic grid,the composition of micro-network hardware platform,using 32-bit fixed-point TMS320F28027 DSP control.The hardware circuit and software program of inverter power supply are programmed in C language.The experimental results show the effectiveness of the control method.