| Nowadays,the global community is facing a critical period of energy-structural transformation and development.On the one hand,the total energy demand of the whole society continues to rise,and it is difficult for the decreasing fossil fuel to support the long-term rapid development of the economy;on the other hand,the gas emissions caused by burning fossil fuel has,to some certain extent,led to some environmental problems,such as air pollution and global warming.Therefore,worldwide governments and organizations are developing new forms of generating electricity,in order to significantly increase the proportion of renewable energy in energy consumption.However,the generation power of renewable energy,represented by photovoltaic power and wind power,is often affected by meteorological conditions,and the generation power shows strong intermittency and volatility.Therefore,the large-scale integration of renewable energy with huge volatility may bring detrimental impacts on the safe and stable operations of the grid.With the development of energy storage technology,it will be an effective way to stabilize the power fluctuation and improve the grid efficiency as well as the penetration rate of renewable energy by bundling energy storage system with renewable energy generation devices,installing appropriate energy storage system at key buses,and performing appropriate energy storage control strategies as a whole.Therefore,this paper studies the energy storage configuration strategies for stabilizing power fluctuation in tie-line,smoothing wind power and optimizing the operation of the power system from the perspective of the power side and the grid side.Furthermore,the paper provides solutions to sizing the energy storage system for the renewable energy power station and the power grid.The main contents of the important research carried out in this paper are:1.Based on the ideal low-pass filtering method,the research shows the historical data and sampling frequency selection problem for sizing energy storage system in the case of stabilizing power fluctuation the tie-line.According to the established energy storage sizing model considering the operational continuity constraints of the energy storage system and the state of charge constraints,the optimal energy storage configuration results at different time scales are calculated based on different smoothing requirements.Meanwhile,based on the spectrum analysis of the historical power data and the sizing the results of energy storage system,the paper shows the appropriate time scales of histrical data which can be used to calculate the configuration of the energy storage system.The research can serve as a reference not only to size energy storage system in the case of stablizing power fluctuation in tie-line but also to formulate the standard of setting fluctuation rate.2.Based on the moving average filtering method and Savitzky-Golay filtering method,a set of energy storage sizing methods are provided from the viewpoint of stabilizing the fluctuating power in tie-line.According to the data of the typical day’s fluctuating power in tie-line,the optimal size of the energy storage system is calculated based on the sizing strategy related to different digital filtering methods,including time-domain filtering methods and the ideal low-pass filtering methods.The kernel structure of filters for sizing energy storage system are compared in both time domain and frequency domain.Besides,the paper also shows the function of different filtering methods in smoothing fluctuations and discusses the avability and the limitation of the proposed energy storage sizing methods based on the digital filtering methods.3.In order to smooth the output power of the wind farm flowing into the power grid,the paper shows a control strategy for energy storage system with energy conversion loss to make wind power system more dispatchable.The energy storage control strategy consists of two parts: at the beginning of each dispatch period,the controller calculates the setpoint power by referring to the state of charge of ESS and predicted average wind power in the scheduling period;within the dispatch period,the controller adjusts the charging and discharging power of the energy storage systems according to the sampling power by the model predictive control strategy,so that the wind energy storage system can track the set-point power.Based on the control strategy,an engineering energy storage configuration method for wind farms is proposed without considering the operation constraints of energy storage system.4.An energy storage configuration method is proposed based on the control strategy of the wind storage system considering energy storage operation constraints.During the dispatch period,the Hildreth algorithm is used in solving the model predictive control problem which is a typical quadratic programming problem with energy storage operation constraints.The algorithm has strong computational stability and can solve the quadratic programming problem quickly.According to the proposed control strategy,the average fluctuation rate of the wind storage system with different configuration capacities of energy storage system is calculated,and the results are visually presented in a sizing decision map.Based on the control model,the average volatility index of the system optimization scheduling under different energy storage configuration combinations is calculated,and the energy storage configuration decision map is drawn.The most economical size of the energy storage system is determined by referring to the curve of preset the dispatch fluctuation rate on the decision map.5.From the perspective of optimizing the operation of the power system with an energy storage system,this paper proposes an approach of calculating the optimal operation and size of Energy Storage System by considering the correlation of predictive error of dispatchable resources,such as wind power and load demand.The major problem is to minimize the sum of the average investment cost and operating cost during the operation period by optimizing the energy storage system capacity and operating data.In order to solve the optimization problem,the established mathematical model of the dispatchable resources considering the correlation of the prediction error needs to be used to transform the chance constraints into a linear constraint.In the model,two types of transmission line overloading constraints,including two-sides constraints and scenario generation constraints are established.Besides,the paper also provides the corresponding approaches to linearizing the chance constraints.In the planning,the optimization model can be established according to the operational requirements to optimize the energy storage size and the operation data,finally balancing the operational safety and economy. |
