| Due to continuous reduction of fuel energy and increasingly serious harm to the environment,human have turned their attention to renewable energy sources such as solar energy and wind energy.Technology of distributed generation based on renewable energy has been an important direction for future development of electric power industry.Islanding is a basic problem in distributed generation system.Island refers to a phenomenon when the main power system is in failure,distributed generation system continues to work,provides power to local load independently.Islanding threatens the safety of the maintenance personnel,affects switch action of distribution system,and may bring damage to electrical equipment.Therefore,islanding detection is a must protection device in distributed generation.The number of inverters increases with the increase of photovoltaic power station capacity.Multi inverter grid connected system brings more problems.Therefore,this thesis studies islanding detection of multi inverter system.The main points are as follows:(1)This thesis describes islanding detection methods based on grid connected inverter,and analyzes passive and active islanding detection methods.This thesis analyzes advantages and disadvantages of several active frequency shifts such as islanding detection methods which are widely used at present.(2)This thesis researches multi-inverter islanding detection method,and analyzes the applicability and detection performance of AFD method,SFS method and SMS method in multi inverter grid connected condition.(3)This thesis researches NDZ and the dilution effect of active islanding detection methods in multi inverter grid-conected system,and analyzes the principle of the dilution effect in multi inverter islanding detection and then simulate.Research on multi inverter grid connected islanding detection method based on wavelet transform and support vector machine. |
PDF Full Text Request