Research on Impact of the Direct Drive Wind Farm on Power System Relay Protection
|Keywords||Permanent magnet direct drive wind turbine Grid-connected wind farms Neutral grounding S-function Distance protection|
With the wind power technology development and the increasing attention torenewable energy in China,our country’s wind power industry attracted worldwideattention with its remarkable achievements. In current dominant VSCF(variable speedconstant frepuency) wind turbine,the permanent magnet direct drive wind turbinebecomes the mainstream model in the wind farms for its numerous advantages. Theregion where wind power resource is rich but the grid is weak, with the increasingcapacity of wind power integration and the insufficiency of grid regulation,the wind farmwill have a negative impact on the protection devices where the power grid accessed, andresulting in the malfunction of the protection.Based on the former and present researches and combined with the data from adirect-drive wind farm, the paper uses Matlab software to build simulation models,andresearch the effect of the direct-drive wind farms to the relay protection in the power grid.This paper mainly focuses on the following aspects: First, based on the actual situation ofa wind farm,uses the four component method simulating the actual wind speed, andconstructs the reasonable direct-drive wind machine transmission mechanismmodel,especially analyze the steady state model and the state equation under thesynchronous rotating coordinate system of permanent magnet synchronous generatorused in a direct-drive variable speed wind turbine manufactured in China,and amathematical model and control strategy of the converter is introduced.Second, Through the actual measurement and the calculation data analyzes thesituation of the grid-connected direct-drive wind farms,and explains the impact to thelocal grid voltage stability and protection devices.Then basing on the basic principles andthe actually measured data of the distance protection and using the Matlab software tobuild simulation model,the paper compiles the S-function of distance protection.Finally,the paper studies the impact imposed on the relay protection by thegrid-connected wind farm model which built by the Matlab simulation software. Theresult shows the following situations will have some impact on the grids which affecting the relay protection: the moment of the direct-drive wind farms connect with powergrid,the ground faults of power grid occur in the grid-connected wind farms,the suddenchanges of wind speed,and the short circuit and off network accidents in the wind farms.The simulation results provide a reference for the re-design of the protection program.