Research on frequency control of micro-grid

Abstract

For the past few years, micro-grid obtained rapid expansion with the growing concern on renewable energy, efficiency and reliable power supply and economic savings. It plays an important role in harmonize the contradiction between distributed generation (DG) and main grid. But when active power vacancy happened, strong fluctuation will be triggered due to the own features of micro-grid. This fluctuation may affect the system’s reliability and power quality.

The source of power (distributed generation) is the most difference between micro-grid and traditional grid. Due to the wide range of control methods and running characteristics of DG, this thesisanalyzed the typical control strategies of DGs (P-Q, V-f, droop control and synchronous machine control system). And the frequency control abilities of different DGs were determined by simulations in Matlab/Simulink.

Every micro-source has its effects on the frequency characteristics of micro-grid. So this thesis analyzed what are their affections in micro-grid based on the previous studies of the power-frequency characteristics.Through analyzing the frequency characteristics of MS, the frequency characteristics of MG can be accurately grasped. It is the basis for study the related control strategy to ensuring the security and stability of the MG system.

Finally, based on thoseground works, the frequency modulation characteristics of multiple DGs cooperation were discussed and the frequency control strategies of MG system are studied.