Research On Unified Active Power Optimal Switching Control Strategy Of Wind Farm Under Wake Effect

Under the guidance of the "double carbon" target,the installed capacity of wind power continues to increase,and wind power becomes one of the main forms of power generation in the future.With the development of wind power technology,the scale of wind farms is expanding,and the impact of wake effect on wind farms cannot be ignored.The wake effect will reduce the wind speed of the downstream wind turbines in the wind farm and reduce the output power of the downstream wind turbines,thus reducing the overall output power of the wind farm.Therefore,in this topic,the wind farm composed of doubly-fed induction wind turbines is studied for the optimal control of its active power considering the effect of the wake effect,and the specific work is as follows:Firstly,a mathematical model of the double-fed induction generator(DFIG)and the wind turbine is developed.The operational characteristics of the doubly-fed induction wind turbines are described,the implementation method of its maximum power point tracking(MPPT)mode is analyzed,and the frequency support control technology is studied,laying the foundation for the subsequent implementation of the active optimization strategy.Secondly,the Jensen wake model is used to analyze the wake wind speed distribution of wind turbines for the calculation of wake wind speed in large-scale wind farms.For the superimposed wake phenomenon caused by wind direction change,the calculation method of shadow area under different superimposed wake conditions is proposed,and the calculation of wake wind speed under different natural wind directions and wind speeds is realized.Based on the mathematical model of a single doubly-fed induction wind turbine and the wake effect model,a mathematical model of the wind farm under wake effect is established,and it is analyzed that the output power of the wind farm is only related to the rotor speed and pitch angle under the condition of natural wind speed,and the power regulation of wind farm is achieved by prioritizing the rotor speed control,and then using the pitch angle control after the rotor speed reaches the limit value,so as to avoid the rotor speed exceeding the limit value.The wind farm simulation model considering the wake effect is built in MATLAB/Simulink software,and the captured wind speed,rotor speed,and pitch angle of each wind turbine are compared under different natural wind speeds and wind directions to verify the validity of the proposed wake wind speed calculation method.Finally,because the active power control of wind farms can be seen as an optimization problem due to the tail current interaction between wind turbines,this paper proposes a coordinated optimal active power control method for wind farms with multiple wind turbines under the tail current effect.The control method takes the current state of the wind turbines as the initial state,takes the sum of the total rotor kinetic energy change and the total pitch angle change as the optimization objective,and combines the power change constraint to realize flexible active power optimization switching control of wind farms.The defined optimization objective unifies the kinetic energy optimization at low wind speeds,the pitch angle and kinetic energy trade-off optimization at medium wind speeds,and the pitch angle optimization at high wind speeds.An improved particle swarm algorithm is used to optimize the proposed control method,and a Kmeans clustering algorithm is used to classify wind turbines with similar wake distribution and to assign the same control parameters to the same class of wind turbines,thus reducing the optimization computation and increasing the optimization speed.The simulation results show that the proposed method can flexibly switch the wind farm active targets,optimize the rotor speed and pitch angle of wind turbines at different locations,and improve the system frequency response by releasing rotor kinetic energy and/or increasing the wind farm output power.