Research On Operation Characteristics Of Inverter-based Micro Sources Under The Fault Mode Of Microgrid

Along with the growing shortage of domestic resources and load increasing, microgrid composed of distributed generation has become one of research hotspots in recent years. Safe and reliable operation of microgrid cannot do without precise control and protection. Due to the characteristics of inverter-based micro sources in microgrid, the changes of the electric parameters of islanded microgrid have a big difference with the traditional power grid under fault condition. So it is essential to study the operation characteristics of inverter-based micro sources under different fault conditions of microgrid and their influence on the fault characteristics of microgrid system.At first, the power allocation strategy of microgrid is analyzed. According to the characteristics of the line impedance uncertainty, the droop control strategy based on load voltage feedback is adopted to share the active power and reactive power in the microgrid, and to ensure the stable operation of microgrid. Secondly, the operation characteristics of inverter-based micro sources under three-phase symmetrical fault and phase-to-phase fault condition of islanded microgrid are studied, and the variations of the electric quantity of micro sources are analyzed in detail. For the voltage and current waveform distortion caused by the traditional current limitation in the case of asymmetric fault, the distortion-free current limitation is introduced. Analysis and comparison of two kinds of current limiting methods are carried out. The analysis shows that the method of distortion-free current limitation can reduce the harmonic component in the system obviously. On the basis of analyzing the operation characteristics of inverter-based micro sources under the fault conditions of microgrid, the fault characteristics of islanded microgrid are also analyzed. In addition, a simulation model of microgrid made up of three inverters is established by using MATLAB/Simulink simulation software, setting up the fault parameters and starting simulation, to verify the correctness of the theoretical analysis of the operation characteristics of inverter-based micro sources under the fault conditions of microgrid.The microgrid experimental platform based on digital control by DSP TMS320F28335 is built in the laboratory. The control strategy adopted in the paper and the theoretical analysis of the operation characteristics of inverter-based micro sources under the fault conditions of islanded microgrid are established on the experimental platform. The experimental results verify the correctness of theoretical analysis.