Research On Current Type Seamless Transfer Shceme Designed For Parallel Inverters System

Along with the rapid development of industry and economy around the word,energy shortage problem has gained increased attention.Renewable resource,serving as one important part of the energy supply system,is the most promising research orientation of the future energy development.Among them,photovoltaic generation is the most popular and widely researched technique,which has the advantages of flexible application,zero pollution,high rate of returns and etc.To further enhance the harnessing efficiency of photovoltaic energy,photovoltaic microgrid is introduced to integrate inverter unit,energy storage un it and other form of distributed generation unit,which is self-governed and has good compatibility with the traditional grid.The main contents can be concluded as follows:Further research the drawbacks of traditional mode switch control scheme and reasoning the cause of impulse during the mode switch.The dominant seamless transfer methods in the fields are compared,of which the pros and cons are analyzed.The mechanism of droop control is elaborated and its application in the field of seamless transfer method design is further explored.In order to enhance the dynamic response ability of the traditional droop based seamless transfer scheme,a novel transfer scheme based on unified current controller is proposed in this paper.On the basis of droop metho d,a current type control scheme designed for inverter islanded operation is proposed in this paper.Droop characteristic is integrated in the control and,in the meantime,the current controller is highly unified before and after the inverter mode switch,which will guarantee the seamless transfer to a great extent.Small signal model is established according to the inverter topology and the seamless transfer method.According to root locus analysis,stability of the control scheme is validated and the corresponding stable region of each control parameter is decided.Based on MATLAB simulation software,the discrete model of parallel inverter system is established.Finally,the experimental platform based on DSP28335 micro controller is established,where several experiments have been designed to test the performance of proposed control scheme.Experimental results have validated the feasibility of seamless transfer method during the mode switch.