The Principle And Analysis Of Stability Of Droop Control In Micro-grid

The droop control is the main control strategy when microgrid is off the grid,which can ensure the load power allocation according to the sources' rates,and can acts as a constant power control strategy when the micro grid operates on the grid.This paper divided the droop control structure into two parts,including the droop curve implantation and the terminal voltage control of inverter.The implanted part of droop curve includes power controller and a droop curve equation,and the terminal voltage control part of inverter is aiming to achieve the goal that controlling the output voltage to follow the reference voltage precisely.This paper design the value of power controller and LC filter of droop control,and from the view of closed loop band width,the paper design the value of double closed loop voltage and current controller.It is simulated when the microgrid connects and breaks away from the grid respectively by making use of the droop controller.The simulation results show that the droop control can achieve the distribution of active power load.For the severe decrease in frequency value when micro grid feed heavy load,the paper design the frequency restore strategy,the simulation results verify the frequency restore strategy.At last,the stability of the droop control is discussed under its connection with the network.By establishing the mathematical model of the droop control when the inverter is connected with the network,a nonlinear differential equations are obtained,which can reflect the transient process of the system.This paper studies the transient process of the system under the conditions of different droop coefficients,different line impedances and different initial phases by means of MATLAB numerical solution,and the conclusions obtained are verified by the simulations.