Research On Method And Capacity Allocation Of Microgrid Frequency Characteristics Based On Hybrid Energy Storage System

With the rapid development of smart grid construction and the gradual acceleration of energy substitution,distributed generation has been widely used in regional grids such as microgrids,and has also brought great challenges to traditional power systems.In terms of frequency,due to the intermittent and uncertain nature of new energy distributed power,the power supply and demand balance in the system cannot be guaranteed.At the same time,under the background of high power electronics,distributed power sources such as photovoltaic power sources and energy storage batteries are connected to the power grid via power electronic converters,resulting in a serious lack of system inertia capability.Risk of instability.The introduction of energy storage equipment can alleviate the negative impact of wind,light and other new energy power generation on the system.Energy-density and power-density composite energy storage forms can reliably improve the frequency characteristics of the system,but they are shaped like pumped-storage power stations.Dense energy storage is largely constrained by geographical location and environmental resources.At the same time,there are a large number of abandoned mines in China,and its abundant underground space resources and groundwater resources have created the possibility for small pumped storage power plants suitable for microgrids.This paper first introduces the main problems in the power quality of the microgrid at the current stage and the research status of introducing energy storage systems to participate in frequency regulation at home and abroad.At the same time,the technical characteristics of pumped storage power stations and supercapacitors are separately explained,and the current development and utilization of abandoned mines in China are summarized.Then,from the perspective of the conventional power system,the factors affecting the frequency characteristics of the power grid are analyzed,and the qualitative relationship between the system power supply inertia capacity,frequency modulation reserve capacity,and generator power response speed and the frequency modulation characteristics of the system are obtained.A 220 k V actual power grid was selected to perform a horizontal comparison based on the two indicators of inertial capacity and FM reserve capacity,and the disadvantages of frequency regulation characteristics of the microgrid were obtained through analysis.Based on the traditional FM capability evaluation system,an evaluation index of the frequency characteristics of the system in the face of power steps and continuous disturbances is proposed,which provides a basis for the verification of the method mentioned later.In the context of the micro-grid with high penetration of renewable energy,a frequency control model of composite energy storage with abandoned mine pumped storage power stations was established,and a virtual inertia was introduced into the control link of the supercapacitor to ease its impact on the system after access Negative effects of inertial capacity.An adaptive droop control method based on the state of charge of the supercapacitor is proposed to avoid the problem of secondary frequency drop caused by the difference in capacity and climbing rate during the frequency modulation of the supercapacitor and the pumped storage unit.Simulations were performed in Matlab / SIMULINK platform to verify the correctness of the model construction and the effectiveness of the proposed control method.Finally,based on the actual annual statistical data of a certain area,the daily output curve of typical wind power sources in the area was fitted using statistical methods and BP neural network.Combined with the power consumption habits of the area,the net load curve is obtained,and it is transferred to the frequency domain for spectrum analysis by discrete Fourier transform.According to the operating characteristics of micro gas turbines,pumping units and super capacitors,frequency band division and power allocation are performed,and the allocation results are counted to realize the capacity configuration of each power supply.The thesis contains 41 figures,13 tables and 82 references.