Research On Voltage Control And Reactive Optimal Configuration In Offshore Wind Farms Under Multiple Conditions

As the development of clean energy has become the mainstream of research,offshore wind farms are increasingly becoming the focus of attention,which have abundant wind sources off shore.Offshore wind farms containing high-voltage AC submarine cables have a great influence on the study of reactive power compensation due to their large charging power characteristics.In different operating conditions,the demand for reactive power in wind farms is not the same.When the output power is large or the voltage of the system is drastically decreased,the capacitive reactive power is required to maintain the voltage stability.When theTransmission power is small,or when the power frequency overvoltage is generated,or when it's in island mode,inductive reactive power is needed to ensure safe and stable operation of the wind farm.Therefore,this thesis analyzes the various operating conditions that require the configuration of inductive reactive power in offshore wind farms,and proposes a comprehensive reactive power configuration scheme based on suppression of overvoltage and large island compensation,which is supplemented by dynamic reactive power regulation of double-fed induction generators.Firstly,this thesis analyzes the mechanism of power frequency over-voltage generation in offshore wind farms,and obtains the demand for inductive reactive power compensation.Through the formula derivation,the suppression effect of shunt reactors on the capacity-rising effect at the end compensation is the most obvious.In combination with the structural characteristics of offshore wind farms,it can be seen that the shunt reactors at onshore control centers is the best compensation method and the most convenient operation,the power frequency overvoltage of the sample offshore wind farm under different line lengths is calculated by using the ATP/EMTP simulation platform,and the theoretical derivation results are verified.Secondly,this thesis analyzes the mode of operation of islands which are barely researched,studies the configuration of emergency power source and shunt reactors that are required to be equipped under the operation mode of big Island.The capacity of the emergency power supply should meet the power consumption in the offshore booster station and the fan tower tube.The selection of the shunt reactor should refer to the charging power of the low-voltage side submarine cable,and the selection of the reactor can be selected according to the actual number of double-fed induction generators in the operation mode of the big isolated island.And the power flow and short-circuits are calculated under the configuration scheme through examples.In addition,the voltage and reactive power characteristics of offshore wind farms with double-fed induction generators are studied in this thesis.An immune genetic algorithm that takes into account the end voltage limit of double-fed induction generators and the limit of their reactive power output is proposed to control the readifferent locations in order to achieve the optimal network loss as well as make the voltage ctive power of each generator at and power factor to meet the requirements.After the program of C language,the algorithm is optimized.Finally,based on three conditions above,a magnetically control reactor is used instead of a fixed reactor at the land-based centralized control center,and a fixed capacitor is added at sea booster station to in islanding mode.In addition,the reactive power output from the double-fed induction generators is optimized.Considering the comprehensive reactive power optimization configuration scheme for multiple operating conditions,the simulation platform of MATLAB/Simulink compares and verifies the suitability of the scheme for various operating conditions.The research results provided a certain reference for the planning and design of offshore wind farm projects in the future.