Droop Control Strategy Research Of Microgrid Including D-PMSG

This paper focuses on the Microgrid including a directly driven wind turbine with permanent magnet synchronous generator(D-PMSG), analyses the problems we may encounter when droop control strategy is used in the islanding mode of Microgrid.Droop control strategy is usually used in the grid side converter of the D-PMSG when the Microgrid is operating in islanding mode, so as to distribute the power properly and adjust the voltage and frequency. But the output reactive powers of distributed generation(DG) units will be allocated inaccurately because of the unequal line impedance. In order to alleviate uneven sharing of reactive power, a selection method of droop control parameters is proposed. Analysis results demonstrate that adjusting droop control parameters can wholly compensate for the impact of unequal line impedance on reactive power distribution.Besides, duo to the intermittency of wind energy, the generation power of the D-PMSG is not equal to output power of grid side converter of the D-PMSG. So a DC bus energy storage device is needed to balance the power. A new droop control strategy is proposed in this paper. This strategy can measure the DC bus voltage, adjust the droop control characteristic curve and change the output power to control the DC bus voltage within a rational range and reduce the capacity of the DC bus energy storage device.The small signal model of the improved Microgrid system is established in this paper to analyze the stability of the system. Simulation and experiment platforms are also constructed. Theoretical analysis, Simulation and experiment results demonstrate that the selection method of droop control parameters can improve the distribution of the reactive power and the new droop control strategy can effectively control the DC bus voltage within a rational range and reduce the capacity of the DC bus energy storage device.