Low/High Voltage Ride Through Technology Of Directly-driven Permanent Magnet Wind Power Generator

After large-scale wind turbines accidents in 2011,in JiuQuan,the Low Voltage Ride through Technology arouses great attentions and has been a hot research topic.Many previous studies show that low voltage fault is often accompanied by high voltage fault,and the high voltage fault will cause massive wind turbines off the net.Therefore,the new wind turbines should have operation abilities under both low voltage fault and high voltage fault.Focusing on research on low/high voltage ride through technology of directly-driven permanent magnet wind power generator(DPMSG),this paper mainly completes the following work.Firstly,the general situation of wind power generation at home and abroad and the research status of low/high voltage ride through technology are briefly introduced.The operation principle of the DPMSG is analyzed,and a mathematical model is established for the main modules of the unit.Secondly,a novel coordinated control strategy for low voltage ride through is proposed through the research on the traditional LVRT control strategy.Specifically,during the low voltage fault,maintaining the power balance on both sides of the DC bus makes active power output in generator follow the variation of that in grid side.Through the new coordinated control strategy,the machine side converter control of the generator to reduce active power output and the grid side converter increase the active power output during the low voltage fault.the machine side and the grid side converter work together to maintain the power balance on both sides of the DC bus.The simulation model is established in Simulink and the effectiveness of the proposed novel coordination low voltage ride through control strategy is verified by setting differentsimulation examplesFinally,in order to solve the problem of DPMSG off the grid caused by grid voltage swell,this paper analyzes the relationship between both sides of the power flow change of converter of the DPMSG during grid voltage swell.On the basis of the analysis,this paper presents that the directly current compensation of machine side q axis in high voltage fault reduces the unbalanced power on DC bus.Meanwhile,the grid side converter provides inductive reactive power compensation with the establishment of simulation model to do simulation analysis,and the simulation results verify the effectiveness of the proposed control strategy.