Research On Load Distributed By Capacity Of Wireless Parall Inverter System

With the increasing demand of energy and the depletion of traditional fossil fuels,the development and utilization of new energy is becoming increasingly popular.Solar distributed power generation has been used widely due to the characteristic of huge resource,easy installation and no pollution.Parallel inverter technology,the key technology of distributed power generation,has been paid more attention in academic.Wireless parallel technology using droop control is better than other ones because of higher redundancy,less wiring and more convenient position,the different capacity sizes of inverter in distributed generation system exists.In order to make full use of each inverters,it is an urgent task to carry out the reasonable load distribution for the inverter with different capacity.Discussions and analysis have been paid to the problem in this paper,for the sake of critical droop coefficient of system convergence and a sufficient condition when different capacity inverters paralleled by reasonable capacity distribution,The amplitudes and frequencies of the output voltage of the inverter have been dynamic analyzed based on droop control principle.Firstly,the working principle and mathematical model of single-phase full-bridge inverter are introduced in this paper.Control strategy,selection of parameters of voltage and current loop and algorithm with nonlinear load is designed and optimized.Simulation is built to verify its effectiveness.Secondly,the emphasis is placed on the capacity allocation in different capacity inverters,Mathematical Modeling of the parallel circuit including droop control principle which was introduced in the following was established.Then,on the basis of the droop control equation,dynamic equations of output voltage amplitudes and frequencies of inverter is made up by constituted simultaneous output power equation of inverter after filtering.A sufficient condition about inverter power distribution load according to its own capacity is got via analysis the output voltage amplitude and frequency convergence of inverter.The simulation and experimental platform are ultimately used to verify the sufficient conditions of the parallel load distribution in different capacity inverters.Finally,system’s hardware and software is designed in this paper.In hardware,the selection of the DC bus capacitor,the type of the switch tube and the design of the drive circuit and snubber circuit as well as selection of the parameters of the LC filtercircuit are mainly discussed.While in software,it contains introduction of the main program and interrupt program flow chart,the discretization of low-pass filter and repetitive control and the digitization of PI algorithm.The design of output impedance are introduced and particularly verified by simulations and experiments which show that the voltage distortion rate of system with nonlinear load and the odd harmonic impedance of the system are substantially reduced.