Research On Hybrid Energy Storage Control Strategies For PV Microgrids

In the past few years,the steady development of PV power generation and energy storage technology,PV-hybrid energy storage-based DC microgrid has gained the attentiveness of many academics at home and abroad.Given the intermittency and variability of photovoltaic power production and the various load switching operations,the DC bus is subject to power fluctuations,which leads to DC bus voltage fluctuations.This is achieved by a hybrid energy storage system that has multiple loading and unloading capabilities,effectively suppressing both high and low frequency components of power fluctuations and maintains the DC bus voltage through regulation of the two-way energy flow between the energy storage devices and the direct current busbar.Consequently,Taking the hybrid energy storage system as the research subject,the thesis focuses on the mixed energy storage power distribution problem as well as direct current busbar voltage control strategy.The details are as follows:(1)The first section describes the context and significance of the chosen theme,as well as the cutting-edge technology in energy storage,A concise explanation of DC microgrid and the latest status of research in the field of photovoltaic production technology.After that,each section of the optical storage microgrid system is modeled,it contains computational modules for battery and supercapacitor energy conservation units and for bi-directional DC-DC inverters.The fundamental control theory of the hybrid energy storage system is furthermore analysed in principle and its limitations are pointed out.(2)For hybrid energy storage power allocation,a fuzzy adaptive hybrid energy storage power allocation strategy based on supercapacitor SOC is suggested.To eliminate the issue of loading and unloading the mixed energy storage unit,Due to the low power consumption density of supercapacitor,its charge state SOC is easy to reach its upper and lower limits and may overcharge and excessive discharge.Fuzzy control is used in the power distribution process to adjust the filtering time parameter by virtue of the supercapacitor charge state and its reference power,in order to achieve a reasonable adjustment of the unbalanced power distribution.At the same time,it ensures that the charge state of the energy storage device is always within the normal operating range,avoiding the problem of its overcharging and discharging.Verification of the correctness of the policy is by means of Matlab simulation.(3)Finally,A possess policy is proposed for the direct current busbar voltage waves on account of an improved active disturbance rejection control.The structural principles and control components of self-turbulence control are presented,and the difficulty that the control behaviour of conventional self-turbulence control is limited by the bandwidth of the observer is pointed out.Thus,an improved LADRC based on the introduction of the total disturbance differential is proposed on the basis of the active anti-jamming control method and installed to further enhance the stability in the voltage regulating circuit and anti-interference resistance of the DC bus voltage and obtain the stability of the DC bus voltage.Finally,the rationality frequency domain comparison and the Matlab time domain simulation model are used to confirm the validity of the possess policy designed in this chapter.