Research On Islanding Detection Method Of Microgrid Inverter

In response to the challenges of energy security and environmental pollution,renewable energy,such as solar energy and wind energy,has been paid more attention and widely applied.The randomness and volatility of the distributed generation will affect the stability of the power grid and limit its performance,and the microgrid constructed by multiple distributed power can make up for these deficiencies.The control and protection strategies of microgrid are the foundation of giving full play to the advantages of microgrid,among which preventing the occurrence of islanding effect is an important measure to protect the maintenance personnel and equipment.Therefore,it is very significant to study the islanding detection methods of microgrid.Firstly,the advantages and disadvantages of single inverter system islanding detection method based on the analysis of the micro grid inverter are compared in this paper,the law of islanding detection method for the microgrid multi inverter has been discussed,and a kind of negative sequence voltage positive feedback detection method based on THD online measurement is put forward aiming at the dilution effect of microgrid Multi-Inverters in parallel connection.Secondly,the switching control strategy of the master-slave structure of micro grid inverter is studied,its mathematical model is deduced and loop parameters is designed,meanwhile,the way to realize online measurement of the THD and voltage unbalance,the FFT sampling frequency and the selection basis of the length of the sequence,the advantages and disadvantages of Double Second Order Generalized Integral and Delayed Signal Cancellation for extraction of positive and negative sequence components.Simulation bas been done in the Matlab/Simulink environment with the islanding detection method proposed in this paper.Finally,a prototype of 15 kVA microgrid main inverter is developed,and the design process of hardware and software is introduced.The correctness and validity of the proposed islanding detection method are verified by experiments.