Research On Power System Net Load Optimization Dispatch With Large Scale Wind Power Connection

Recent years,the fossil energy sources are getting shortage.The climate and environment constraints are also getting tight.A new round of energy revolution oriented towards green and low-carbon has risen up luxuriantly.Meeting the power electricity demand and highlight the clean and green energy development are the basic principles of China's power industry.With the exhaustion of fossil energy resources,the renewable energy represented by wind energy,solar energy and water energy will gradually become the dominant energy.Renewable energy resources are abundant and their natural characteristics with randomness and fluctuation in time and space distribution bring new difficulties and challenges to power grid energy balance control with their participation in system regulation and control.Facing the problems bring by large scale wind power access to the power system,this thesis focuses on the net load as dispatch object formed after all the wind power consumed by the conventional power load and further study the power system optimization dispatch methods.In the traditional day-ahead power dispatch,the dispatch time scale is always set as one hour to make the dispatch strategy.With the increasing proportion of wind power generating,the uncertainty and volatility of the power outputs make the power balance more difficult.Thus,in order to meet the power balance demand,in the fossil energy based power system,thermal power generators need to adjust their outputs to response to the wind power outputs frequently,which will cause the stress variation of the boiler tube and thermal fatigue damage and even cause the explosion.In view of the above problems,this thesis proposed a time division method of net load time series based on the random matrix theory.The changing characteristics of net load are analyzed based on the random matrix theory and the stability abrupt transitions of the net load are studied.Thus,we can achieve the segmented points of the time series.Based on the time division,a numerical characteristic extraction method through empirical mode decomposition is given.Moreover,the complexity of net load is calculated by the sample entropy.In addition,a comprehensive quantification index considering the numerical characteristic and the complexity is provided.The provincial data and net load of a province in the northeast in China is utilized to verify the rationality and effectiveness of the proposed methods.In order to reduce the ramp operation of the thermal generators caused by the fluctuations of net load,decrease the ramp operation cost,extend the continuous and steady operation time of thermal generators and improve the operation stability of the system,a power system source-load interaction power dispatch strategy based on the time series characteristics of net load is proposed.Making the comprehensive consideration of the operation characteristics of thermal generators and energy storage systems,the thermal generator operation modes and dispatch strategy are made.On the basis of ensuring the operation stability of the power system,this strategy can make full use of the generating flexibility of pumped storage and battery energy storage to assist to response to the net load variation.The interactions between the energy storage system and wind power are improved and the participation of the energy storage system is increased.Thus,the economic operation of the system is realized.In the power system with large scale wind power access,fully utilization of the demand side resources and realization of source-load interaction is one of the main means of wind power consumption.The rapidly development of electric vehicles make the retired batteries available as a new kind of flexible loads to participate in the power dispatch.In this thesis,a source-load interaction optimization dispatch considering the generating risk of retired batteries is proposed.The characteristics of second life batteries are studied based on the experiment data.The equivalent circuit model is designed and the upper limit of charging and discharging capacity of retired battery energy storage system is given.Due to the differences among battery cells in the retired battery energy storage system will affect the overall charging and discharging capacity,q quantitative method for evaluating the consistency of the retired batteries based on information entropy theory is proposed.The risk comprehensive index of the system operation is proposed considering the retired battery operation risk and uncertain risk of wind power outputs.Further,a source-load interaction optimization dispatch model considering the generating risk of retired batteries is built.In the model,the risk index is taken into account and the safety and reliability of the system are improved.The opportunity cost of retired batteries are calculated,which can reflect the economic and environmental friendly of the provided dispatch strategy.Finally,the reasonability and validity of the proposed time division method,thermal operation mode based on the net load characteristics and the source-load interaction dispatch considering risk index are verified on the real network data of a provincial power grid in the northeast of China.The results show that,the proposed power system optimization dispatch method can take into account the operation stability of thermal power generators,reduce the operation risk of the system,promote the interaction between energy storage system and wind power and achieve the stable and economic operation of the system.