Research On Energy Balance In DC Microgrid

As the burning of fossil energy causes environmental problems and energy crises to intensify,countries around the world are facing the shortcomings of traditional power generation methods and are gradually paying attention to new energy power generation technologies represented by wind power and photovoltaics.DC microgrid can fully absorb new energy,but the intermittent and random nature of distributed power generation technology will cause uneven power and power quality problems.In order to maintain the stable operation of the system,energy storage units are widely used in DC microgrids as a means to eliminate power fluctuations.Due to the limitations of a single energy storage element or a single energy storage system,in practice,multiple hybrid energy storage systems are often used to meet system requirements.This paper selects the hybrid energy storage system in the DC microgrid as the main research object,and focuses on the energy balance in the DC microgrid.First,the current structure of DC microgrid is compared and analyzed,the mathematical model of the energy storage unit is established to discuss its working characteristics,and the topology and working principle of the DC/DC converter are studied to provide a basis for the study of control strategies.Secondly,the hybrid energy storage system using traditional droop control strategy is analyzed,and it is found that the line impedance is the root cause of its steady-state energy unevenness and transient power distribution problems,and the control strategy leads to inherent defects that affect the quality of the bus voltage.Discussed the pulse injection type active impedance detection method and the bus voltage translation compensation control strategy.Finally,in view of the power output jump,uneven load current distribution and bus voltage stability of the energy storage unit in the hybrid energy storage system in the DC microgrid caused by the line impedance,an adaptive and improved droop control strategy that actively detects the line impedance is proposed..Real-time detection of line impedance and correction of the control droop coefficient can effectively improve the power output characteristics between different units of the hybrid energy storage system,and realize dynamic current sharing control between multiple hybrid energy storage systems,and introduce a voltage compensation factor to realize the translation of the bus voltage make up.Ensure the adaptive and coordinated operation of each energy storage unit in the DC microgrid without communication,and improve system stability and redundancy.Through the use of Matlab/Simulink software simulation and experiments based on the RT-Lab platform,the correctness and effectiveness of the proposed control strategy are verified.