Research On Wireless Parallel Technology Of Photovoltaic Inverter Allocated Power By Capacity

Recently, under the dual pressure of energy shortage and haze problems, the nation actively promote the development and utilization of new energy, one of the most development potential is solar power.Photovoltaic distributed generation applicated in the roof of the building and agricultural facilities,we can use the local renewable sources clean and efficiently. In order to make full use of the solar energy and form a redundant power supply system, the distributed power supply can be connected in parallel to form a micro grid through an inverter interface.So the steady operation of parallel inverters can improve the overall capacity and reliability of the power supply system.For the parallel connection of different capacity power supply, it is required to match the corresponding power level inverters, and design the control parameters to achieve the load distribution according to the capacity.To solve these problems, this paper analyzes the wireless parallel connection of different capacity inverters, and especially study the convergence of the parallel system.Firstly, the paper analyzes the research status of parallel control methods, and compares the advantages and disadvantages of them,thus adopts the droop control strategy.Secondly, in order to realize the stable and reliable operation of the parallel power supply, the analysis of the single inverter is carried out. by establishing the mathematical model of the single-phase full bridge inverter, we design the LC filter and double loop PI controller, In order to reduce the steady-state error of the sinusoidal signal,the paper add repetitive controller in double loop control system.then the simulation and experiment results verify the effectiveness of the controller design.It lays the foundation for parallel inverter control.Thirdly, establishes the parallel equivalent model,and obtains the output power expression of the inverter, In order to improve the distribution accuracy of power, the equivalent output impedance is designed to be resistive.After that the paper combines with the low pass filting power expression and droop control equation,then obtains the critical value of convergence and the sufficient condition of power allocation.Finally,the computer simulation is built to verify the theoretical analysis results, and the dynamic characteristics of the parallel system are investigated.Fourth, analyzes the detailed design method of the output impedance, two methods of power calculation, and the strategy of inverter incorporated ACbus.Fifth, in order to validate the analysis of droop coefficient convergence of parallel system, and the effect on practical application,the paper design the parallel system from the two aspects of hardware and software,and build the experimental prototype with two power levels.Finally, the experimental results proved that the paper conclusion has a good guiding significance for the practical application.