Research On Primary Frequency Regulation Control Strategy Of Large-scale Wind Power Cluster

With the continuous improvement of wind power penetration,the power system's ability of only relying on traditional power frequency regulation is continuously weakened,which not only brings difficulties to the dispatching operation of power system,but also poses a potential threat to the safe and stable operation of power system.Therefore,it is an urgent problem to study the primary frequency regulation control strategy of large-scale wind power cluster.Through the participation of wind power in the primary frequency regulation of the system,not only the frequency response ability of the power system can be improved,but also the rejection rate of wind power can be reduced.In this paper,the primary frequency regulation control strategy of large-scale wind power system is studied from the aspects of the level of wind turbine,the level of wind farm and the level of power system.The main work is as follows:At the level of wind turbine,this paper puts forward the whole wind speed control strategy of wind turbine.The virtual inertial control and droop control are combined to realize the frequency modulation control of the low wind speed section of the wind turbine,and the speed recovery control of the rotor after releasing the kinetic energy of the rotor is carried out to avoid the possible secondary frequency drop.The pitch angle control is adopted in the high wind speed section,and the pitch angle control flow chart is given.Different pitch angle increment is calculated according to different frequency deviation.The common control of high and low wind speed sections realizes the participation of wind turbine in system frequency adjustment in the whole wind speed section.At the level of wind farm,this paper proposes the optimal allocation method of reference value of wind turbine frequency regulation power.The grouping rules are made according to the different operating conditions of wind turbines,and the weight factors are set for each wind speed segment,and the power distribution strategy of each wind turbine in the wind farm based on the weight factors is established.Different frequency regulation power is given for different wind speed segments,and the optimal allocation of frequency regulation power in large-scale wind farm is realized by giving full play to the frequencyregulation ability of each unit.When the wind farm exits the frequency regulation stage,the active increment is used as a trade-off index to determine the initial time when the wind turbine exits the frequency regulation in different wind speed segments and the delay time interval between each wind speed segment.Finally,the simulation model of two regions and four units is built to verify the effect of the control strategy on the frequency fluctuation with the sudden increase of load as the disturbance,and the results show that the grouping strategy and the wind turbine orderly recovery strategy have a positive effect on improving the system frequency fluctuations.At the level of power system,a control strategy of large-scale wind farms cooperating with thermal power plants to participate in the primary frequency regulation of the system is proposed.The control framework of wind-thermal cooperative frequency regulation is constructed.Combining the characteristics of small inertia and fast response speed of wind turbine and coordinated with the thermal power plant,the dispatch center allocates system power shortages to wind farms and thermal power units in real time according to the operating status of the wind farm and thermal power units and the change of system frequency.Then,the wind farm sends the frequency regulation task to each unit to complete the primary frequency regulation of the wind-thermal power collaborative power system.The results are verified through the simulation of a 36-node example,which shows the feasibility and effectiveness of wind-thermal power coordinated primary frequency regulation control strategy.The wind-thermal power cooperative frequency control strategy proposed in this paper can give full play to the role of wind farm frequency regulation,and effectively improve the frequency response ability,and provide certain technical support and method guidance for power system scheduling with large-scale wind power.