| In order to achieve the "30·60" double carbon target on schedule,the power system is required to accelerate the pace of energy transformation,and vigorously developing wind power and other green power gradually replacing coal-fired power generation will be the key to achieve energy transformation.Due to the instability,randomness and intermittency of wind energy,and wind power is a cubic function of wind speed,so wind power has a strong volatility.Large-scale grid-connected wind power fluctuation seriously affects the power quality and safe and stable operation of the grid.Therefore,it is necessary to take measures to smooth the wind power fluctuation to a limited range before safe grid-connected.This paper makes an in-depth analysis of the current research status of using energy storage technology to smooth wind power fluctuations and determines the configuration of mixed energy storage for wind farms to smooth their output power fluctuations.In this paper,the time-frequency analysis of wind power fluctuation is firstly carried out,and then the wind power fluctuation calming strategy,frequency division of hybrid energy storage power and power capacity optimization configuration are mainly studied for hybrid energy storage configuration.First,the time-frequency analysis of wind power fluctuation is carried out.The mathematical model of wind power generation is established and the cause of wind power fluctuation and its influence on power grid are analyzed.The time domain analysis of wind power fluctuation is carried out by means of mathematical statistics.It is found that the longer the time scale,the larger the amplitude of wind power fluctuation and the more dispersed the distribution.Fourier transform is applied to wind power signal,and the amplitude-frequency characteristic curve shows that the energy of wind power signal is mainly concentrated in the low-frequency part with very narrow frequency band.According to the wavelet packet decomposition results of wind power signal,the low-frequency curve is smooth and the trend change of the original wind power signal is tracked on the power amplitude.Although the high-frequency part with narrow frequency band has oscillation,the amplitude is very small,which has little influence on the original wind power.The middle frequency band oscillates around the zero value with a large value,indicating that the middle frequency oscillation is the main reason of wind power signal fluctuation.Then,the strategy of wind power fluctuation is formulated.In the first step,the adaptive sliding average algorithm is used to smooth the original wind power.The algorithm can automatically find the sliding window that enables the output power to meet the fluctuation limits of the one minute and ten minute time scales.In the second step,VMD algorithm is used to allocate the target output of hybrid energy storage to power storage and energy storage according to high and low frequency.Aiming at the problem that the sum of two kinds of energy storage outputs after frequency division is less than the output of mixed energy storage targets in some periods,this paper improved the high and low frequency reconstruction link of VMD algorithm,and simulation verified that the sum of high and low frequency power obtained by frequency division of the improved VMD algorithm can completely track the energy storage target output in the whole cycle.At the same time,the topology design of the combined operation system of air storage is analyzed.Finally,the multi-objective optimization function is used to configure the energy storage capacity.An energy storage capacity configuration model is established with the optimization objectives of reducing the cost of energy storage configuration and maximizing the actual energy storage output to track its expected output.MOHHO algorithm and NSGA-Ⅱ algorithm were used to solve the problem respectively.The results show that MOHHO can greatly save the optimization time and appropriately reduce the cost of energy storage configuration.Simulation shows that the actual output of energy storage fully tracks its expected output,ensuring that the energy storage SOC does not exceed the limit.The energy storage capacity configuration is carried out with different fluctuation limit standards,and the results show that reducing the suppression requirement can reduce the energy storage power capacity configuration and thus reduce the configuration cost. |
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