Research On Power Grid Frequency Control Considering The Uncertainty Of Wind Power

With the rapid development of wind power technology,wind power resources have occupied a key position in the energy structure of our country.At present,the wind turbines itself are isolated from the power grid frequency,and can not make effective response to the power grid frequency as tradyional synchronous generators do.To this end,there have been a large number of academic research and engineering practice to use additional frequency control links to achieve the target of the wind turbines participating in the frequency control of system.However,it is noted that the wind power is uncertain,and the uncertainty of the wind power can cause significant effect on the primary frequency control of system of the wind turbines.Therefore,this paper makes a detailed analysis of the influence and gives the preliminary countermeasures.Based on this,the main research content and results of this paper are as follows:1.The influence of DFIG on the frequency adjustment of power grid is analyzed.The influence of different wind power permeability in the system on the frequency adjustment of the power grid is discussed,and the simulation platform is set up on the basis of the standard IEEE 14 node system model.It is indicated that the overall power system inertia and the unit power regulation capability will be gradually weakened with the gradual increase in the permeability of the wind power.2.The calculation of the frequency modulation reserve capacity of power grid considering the uncertainty of wind power is analyzed.Firstly,wind farms with different normal distribution models are set up in the power system.Secondly,on the premise of wind farm load reduction operation,the size of the reserve capacity of original planned which the wind farms with uncertainty provided is calculated.Finally,in the full use of wind power resources,this paper calculates the total reserve demand of the power system,the amount of spare support which wind farms can provide,and the spare capacity which conventional thermal generators also need to provide under the condition of load reduction in the full time and in the case time according to the typical daily load scene,the calculated size and the confidence probability preset.Theoretical analysis shows that: According to the upper limit level of reserve capacity provided by conventional thermal generators,it can determine whether wind farms are required to run down in this period.Therefore,in the full period of time,the wind turbines can keep the reserve capacity of active power at all the times,and this capability really reduces the standby pressure of the thermal generators at all times.In the case period of time,it can make wind turbine full operation when not needed,and reduce the amount of operation when needed.So,this strategy not only can avoid the shortage of spare thermal power,but also can provide some system spare to reduce the standby pressure of thermal generators during these period,and to achieve the target of making full use of various resources in power system.3.The strategy of DFIG taking part in the system primary frequency control considering the uncertainty of wind power is analyzed.And in order to observe the effect of simulation control,the proposed control idea is applied to the interconnected power grid connected by HVDC.On the premise of using the integrated power reserve control,the simulation verification analysis shows that: When the uncertainty of wind power is not considered,DFIG’s active power will be adjusted according to the load disturbance,and it will assist thermal generators to participate in the primary frequency control.When the uncertainty of wind power is considered,in the case of power shortage,DFIG will determine the amount of active power support in the actual circumstances would whether meet the amount of active power support in the forecast circumstances or not according to the predictive power response which wind turbine receive and the actual residual active power reserve which wind turbine has.There,it can reflect the uncertainty of the wind speed(the actual wind speed is higher,equal to or lower than the predicted wind speed),and can reflect the uncertainty of the amount of active power support of wind turbine(the actual amount of power response is equal to or lower than the predicted amount of power response),and also can reflect the uncertainty of the amount of active power output of conventional thermal generators(the actual active output is equal to or higher than the predicted active output).In addition,the coordination of ultra short term primary frequency modulation capacity between multiple wind farms which are located in the same wind power center can achieve better performance than using these wind farms independently,such as further reducing the frequency control pressure of thermal power units by making full use of wind power resources in the system.