Study On The Control Strategies Of Microgrid

The microgrid is a variety of micro-source combination of low-voltage power grid to provide electric power for the local load. The majority of micro-source is connected with the main grid inverter interface, while reducing the inertia of the system, but the control flexibility of micro power increase. Operation of islanded and grid-connected microgrid is two typical mode of operation, improve the reliability of power supply, but also increased the difficulty of control system in terms of frequency, voltage and energy balance.The diversity of network operation mode and the lack of inertia increases the system control difficulty in maintaining stable frequency and energy balance.Current research on the micro source for various types of control methods in two different modes of operation is relatively mature, but in the two kinds of mode switching process less.This paper mainly studies the method for control of microgrid in two modes, as well as from the island to the smooth handover of microgrid grid-connected mode control strategy. The main work is as follows:Firstly, summarize two existing microgrid control of main control strategies and the control strategy of the pros and cons of comparison, put forward the realization of the island to the grid-connected mode smooth handoff significance.Secondly, to analyze the droop control characteristics, through the establishment of droop control small signal model, a careful analysis of the influence of cut-off frequency voltage frequency, voltage droop parameters and low pass filter of three parameters for the stability of the system.Then, set up the mathematical model of three-phase voltage inverter in the two-phase synchronous rotating coordinate system; the two operation modes of microgrid independently and grid-connected operation, introduces the double-loop droop control feedback control principle and control based on PQ, and the controller parameters are optimized through confirmation; simulation model, verify the effectiveness of the controller.Finally, this paper studies the microgrid smooth cutting-in control strategy. Analysis of a synchronous device in power system are important role in operation, a suitable P-ω, Q-E droop control of micro power inverter the synchronization controller design. Simulation results show that the pretreatment of synchronous controller can effectively suppress the grid-connected current impact, the microgrid power grid, so as to improve the stability of the system.