Research On Output Fluctuation And Energy Storage Capacity Allocation Of Photovoltaic Power Generation Under Multiple Time Scales

As the proportion of photovoltaic(PV)installed capacity in the power system increases,the impact of its volatility and randomness on the power quality becomes more and more obvious.Smoothing the output power fluctuations of PV generation can effectively solve such problems.The development of energy storage technology provides technical support for smoothing the output power fluctuations of PV generation.Based on the time characteristics of PV generation output power fluctuations,this paper conducts research on the problem of smoothing the output power fluctuations of PV generation using energy storage systems at multiple time scales.It has theoretical significance and practical value for the contradiction of power quantity imbalance at various time scales in the new power system and the deployment of energy storage systems based on the characteristics of each time scale.The main research contents are as follows:First,investigate the relevant data of a photovoltaic power station in a certain area of Tibet,establish a differential-probability model,and study the fluctuation characteristics of photovoltaic output power at multiple time scales,including second-level,minute-level,and hour-level.Then,study the change rate and amplitude of photovoltaic power output fluctuations at each time scale,the main frequency distribution position of fluctuations,and the changing characteristics of photovoltaic output power fluctuations with different time scales from a theoretical perspective.The results showed that with the increase of time scale,the fluctuation of photovoltaic power output showed an upward trend,and its intensity also increased significantly.The fluctuation showed trend in the time scale,and the main frequency band of the fluctuation gradually reduced.Next,based on the fluctuation characteristics of photovoltaic output power at multiple time scales,the wavelet packet decomposition method is used to obtain the smoothing target of photovoltaic power output fluctuations.A double-layer iterative model of energy storage capacity is established,and the model is solved by using the bisection method,and the discharge depth parameter is introduced to improve the bisection method.As the time scale increases,the required energy storage capacity for the same discharge depth gradually increases.Through numerical analysis,it is found that the required energy storage capacity increases by 4.4 times as the time scale increases from 10 s to 1h.Finally,simulation models of photovoltaic energy storage systems based on MATLAB/Simulink and a semi-physical simulation platform of photovoltaic energy storage systems with STC8A8K64SA12 as the control core are constructed.The circuit design and hardware implementation are completed.Taking the 10 s time scale as an example,the energy storage capacity is controlled to vary,and experiments and simulations are designed.The experimental and simulation results both prove the rationality of energy storage capacity configuration based on the fluctuation characteristics of each time scale proposed in this paper.