Study On Control Strategy For Reactive Power And Voltage Of Offshore Wind Farm Based On Wind Power Prediction

Wind power generation technology,as one of the most mature and promising power generation methods,has attracted extensive attention all over the world.At the same time,with the rapid development of the wind power industry,the problem of system voltage and frequency stability caused by the intermittence,randomness,and uncertainty of wind power generation is becoming increasingly prominent.One of the more prominent problems is the weak coordination control ability of reactive power when the wind farm operates in parallel,resulting in system voltage fluctuation and even system voltage collapse in serious cases.It will be the key issue about how to choose the best reactive power and voltage control strategy to avoid voltage violations in the operation of wind farms.Based on this,considering reducing the voltage violation rate,improving the control timeliness and realizing the optimal distribution of reactive power output,the paper studies the reactive power and voltage control strategy of offshore wind farms.The main research contents are as follows:(1)an offshore wind farm model is established,which takes into account the reactive power and voltage control system.First,the overall architecture of the offshore wind farm is established.Then a model of the offshore wind power generation system is established.At the same time,it focuses on the reactive power and voltage control problem of offshore wind farms and analyzes the reactive power output characteristics of various reactive power regulating equipment in offshore wind farms to establish a reactive power and voltage control system model.Finally,the simulation model of the offshore wind farm is built,and different simulation conditions are set to verify the validity and accuracy of the built offshore wind farm model,which provides a model basis for the subsequent formulation of the reactive power and voltage control strategy of the offshore wind farm.(2)A wind power prediction method at multiple time scales is proposed.First,the influencing factors of wind power prediction are analyzed.Then a kernel extreme learning machine model is established,and the wind speed correction method and particle swarm optimization algorithm are integrated to forecast the hourly wind power interval.At the same time,considering the operating status of the unit and the results of correlation analysis,the minute-level ultra-short-term forecast of wind power is carried out.Finally,taking the historical data of a wind farm as an example,the validity of the proposed prediction method is verified,and data support is provided for the reactive power and voltage control strategy of subsequent offshore wind farms.(3)A three-stage robust var/voltage optimization control strategy for offshore wind farms is proposed.First,according to different time scales and output characteristics of reactive power regulation equipment,a three-stage reactive power and voltage control strategy architecture is established,i.e.,hour level optimal scheduling of discrete reactive power compensation equipment,minute level coordinated optimal scheduling of wind turbines and dynamic reactive power compensation device,and the real-time droop control of wind turbine terminal voltage.Then,based on wind power interval forecast data and ultrashort-term wind power forecast data,combined with the characteristics of wind power and robust optimization algorithms,hour-level and minute-level reactive power and voltage optimization control strategies are formulated with the goal of minimizing system network loss and voltage deviation.At the same time,considering the above optimization results,the decentralized reactive power and voltage control strategy is used to control the output of reactive power regulation equipment in real-time.Finally,the effectiveness and feasibility of the proposed strategy are verified by simulation.