Research On Grid Connected Inverter Control System Of Permanent Magnet Direct Drive Wind Turbine In Microgrid

With the increasing fossil energy and environmental pollution problems become increasingly serious,renewable energy power generation technology has developed rapidly.Distributed power generation technology with its clean,low energy consumption,flexible control and other advantages has attracted wide attention from the international community,but the distributed power supply because of intermittent and uncertain,direct power generation will have a significant impact on the safe and reliable operation of the regulation the distribution network and the whole power system.Micro-grid can be integrated to integrate a number of distributed generation devices(DG),and according to the operating conditions of the power system in the island mode self-healing operation,the practice proved that DG in the form of micro-grid operation or island operation can be reduced Peak load on the grid pressure,and improve the power quality and reliability.The research object of this paper is a micro-grid with direct drive wind power generation system,and the control strategy of grid-connected converter and the control strategy of smooth switching between grid operation and island operation mode are studied.In this paper,the mathematic model of direct-drive permanent magnet synchronous wind power generation system is established,including the model of fan,permanent magnet synchronous generator,machine-side converter,grid-side converter and its DC link,and the wind turbine Pitch angle control,permanent magnet synchronous generator control,converter control strategy.Secondly,the droop control strategy of smoothing in grid and island two modes of switching permanent magnet wind power system.In order to achieve a stable switching to grid connected inverter as the research object,respectively,puts forward improved wind droop parallel operation of microgrid based on droop method of active power and reactive power decoupling control and islanding under the mode of on line drop compensation control strategy.This strategy is realized in islanding mode under random starting load uniform distribution and stable operation,and the output voltage of grid connected mode and the stability of wind turbine maximum power.At the same time the design of grid pre synchronization controller,to ensure that the grid operation cannot be produced the impact of current great power.Finally,a microgrid simulation model including direct drive wind power generation system is built by using Matlab / Simulink simulation platform,and the simulation experiment is carried outbetween the island mode and the grid mode by using the improved sagging control strategy.The results show that the improved sagging control can make the microgrids switch smoothly in both the island and the grid,and the system is stable and prove the correctness of the proposed method.