Research On Control Strategies Of Wind-gas Coordinated Equivalent Power Plant

Wind power has gained rapid development around the world,because wind energy is rich and widely distributed,meanwhile,it can provide clean electric power.However,as more and more wind power are connected to the power grid,its high inter-temporal variability poses significant chanllenges to the power system operations.Currently,two methods are commonly used to cope with such chanllenges.Firstly,a valid operational strategy is the option of wind power curtailment,however,this method can reduce the utilization of wind power and provide little effect of smooth,when the wind power is fluctuated remarkably.Secondly,the controllable power sources and battery energy storage systems(BESS)are installed with the wind farm to compensate for the wind power fluctuation.And the coordinated control methods of wind power generation and BESS,as well as the gas-steam combined cycle power plant(CCPP)are the key ideas in this paper.the coordinated control methods of wind power generation and BESS are studied in this paper.The coordinated control method based on the combination of model predictive control(MPC)and low pass filter(LPF)control have already been proposed in [1].And in this paper,this method is deeply studied to improve its robustness in two aspects.(a)The impact that the wind power prediction errors have on the control method is studied,Taguchi’s Orthogonal Array Testing(TOAT)is utilized in this paper to generate representative testing scenarios for the MPC optimization.Case study demonstrates that the usage of TOAT increases the robustness of MPC optimization.(b)The adaptively adjustment of multi-objective optimization of weighting factors in the coordinated control method of wind farm and BESS is studied in this paper.A dynamic weighting method is proposed in chapter three,which is based on gridding searching method of the optimal weighting factors.In order to determine the optimal weighting factors,an evaluation method by using the membership function and entropy weight method is proposed.Simulation studies demonstrate that,the proposed method has significant effects on the power and SOC control of BESS besides smoothing wind power,by adaptively adjusting weighting factors of each objectives according to the wind power fluctuations,the SOC and the charge / discharge power of BESS.Secondly,the Wind-Gas coordinated equivalent power plant(WGPP)is proposed in this paper.By integrating the wind farm and CCPP in a WGPP,the grid-connected power is controlled effectively,and WGPP can participate in the system schedule as an equivalent power plant.In this paper,the automatic generation control(AGC)control and the economic dispatch strategy of WGPP are studied.(a)In the study of AGC control,two different scheduling modes are proposed in this paper: scheduling track mode and CPS control mode,according to different scheduling targets and connected systems’ scales.In order to take full advantage of CCPP’s performance characteristics,the AGC algorithm based on traditional PI principle is modified.Finally,the RTDS simulation results using field test data and 4 types of wind events validate the feasibility of the two different scheduling modes.(b)And the the economic dispatch strategy of WGPP is studied in this paper.the working state,start-up and shut-down process of CCPP are considered.According to such contraints,a mathematical model of CCPP is established.Based on this model,at the same time,considering the wind power curtailment and demand response,a MPC-based economic dispatch strategy of wind-gas coordinated system is proposed in chapter five in order to maximize the benefit of WGPP.Finally,the simulation results demonstrate that the new strategy can not only make WGPP track the dispatch targets,but also optimize the power generation in WGPP.