Research On Frequency Control Of Wind-storage System Based On Real Time Power Market

Wind power is a new energy power source with the most promising commercial prospect.However the replacement of traditional thermal power plants and becoming the main power supply cannot happen overnight.Meanwhile,the marketization of wind power is hindered by its volatility and unpredictability.The wind power prediction error increases as time evolves,as a result,real-time market has become the most suitable market for wind power.To cater to this trend,it is necessary to develop a strategy which the wind power is allowed to participate in real-time market.Thus the wind power marketization process is promoted.Participation of wind power in real-time market must meet the basic condition of electricity market,which requests that the output of wind power remains same with the bid value during the working period.Moreover,wind farm is requested to participate in primary frequency control.Otherwise not only facing the punishment of market operators,the irregularity of wind farm can also influence the frequency stability of the whole system under the condition of high permeability.Rely on wind-generator-level control to meet the basic request of real-time market is not adequate,so,a wind-farm-level control strategy must be presented.Therefore,a wind-battery frequency control strategy based on real-time market from the perspective of forecast,control and energy storage is proposed in this thesis.In terms of prediction,a time series model is used on the establishment of system frequency fluctuations and wind farm output.Then Kalman filter is used for rolling optimization and modifying.With no need for delving into the physical relationship,this method is able to find the deep connection from the time series data.Therefore the error caused by nonlinear relationship between the wind generator output and wind features such as wind speed is avoided.Using Kalman filter to scroll and revise forecast results is advantageous to calculate a reasonable bid value for a wind farm meanwhile avoid the circumstance that wind farm cannot output the bid value.In terms of control module,this thesis makes full use of the wind turbine's pitch angle control and over speed control to compensate for the volatility and response the primary frequency regulation.In addition,combination of rapidity of speed control and flexibility of pitch angle control,the capacity of energy storage is minimized which results in cost reduction of wind power.In terms of energy storage,battery control index is proposed in this thesis which makes the battery to avoid overcharge and extends battery service life.In the simulation part,MATLAB is used to build the wind turbine model.Then,the prediction of droop coefficient using Kalman filter is verified what's more,the control module is constructed and the ability of wind storage system on the system frequency response is proved.Finally,four control strategies are compared which proves the feasibility and advantage of the proposed strategy in this thesis.